COLE CROPS - College of Agriculture & Natural …...Cauliflower is the most sensitive of the cole...

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Cooperative Extension Service • Michigan State University • Extension Bulletin E-1591 (Revision) • June 1988 60$ COMMERCIAL VEGETABLE RECOMMENDATIONS COLE CROPS Broccoli, Brussels Sprouts, Cabbage, Cauliflower Bernard H. Zandstra, Department of Horticulture Christine T. Stephens, Department of Botany and Plant Pathology Edward J. Graf his, Department of Entomology T his bulletin has been prepared as a guide for commercial production of the cole crops. The cole crops are members of the Cruciferae (mustard) family, which also includes Chinese cabbage, col- lard, horseradish, kale, kohlrabi, mustard, radish, rutabaga, turnip, and watercress. The term "cole" probably originated in ancient Roman times as a name for leafy vegetables in the mustard family, but now we use it primarily for broccoli, Brussels sprouts, cabbage, and cauliflower. They are impor- tant fresh market and processing crops in Michi- gan, with a combined total of about 7,000 acres grown each year. Production The yield figures (Table 1) are based on the experience of Michigan growers over many years. Experienced growers should be able to produce cole crops at good or higher yield levels regularly. Types and cultivars Broccoli, Brussels sprouts, cabbage, and cauli- flower are all botanical varieties of the genus and species Brassica oleracea. Because they are closely related, their culture is similar. However, there are important differences both between and within the botanical varieties. BROCCOLI: Most broccoli cultivars produce good quality heads during cool weather, but only a few are productive at temperatures above 85° F. By selecting cultivars adapted to different environ- mental conditions, it is possible to produce good broccoli from June through October in Michigan. Broccoli plants produce large central heads. After the main heads are cut, the plants produce side- shoots in the axils of the leaves. Most older culti- vars produce many sideshoots, but most recently- developed cultivars produce very few sideshoots. Some new cultivars produce heads on an elon- gated stem, so that the heads are exposed at the top of the plant. These heads are easier to cut and bunch than heads on short stalks, and they are less susceptible to diseases caused by contact with surrounding leaves. Other characteristics to consider when choos- ing a broccoli cultivar are bead size, head uniform- ity, color, firmness, and days to maturity. BRUSSELS SPROUTS: Brussels sprouts require a long, cool growing season to produce good quality buds. Most areas in Michigan are not Table 1. Yields of Broccoli (main heads) Brussels sprouts (buds) Cabbage, fresh market Cabbage, processing Cauliflower cole \ Low 2.5 4 10 25 4 crops in Michigan 'ields—Tons per acre Good 4 5 15 30 7 Excellent 5 6 20 40 10

Transcript of COLE CROPS - College of Agriculture & Natural …...Cauliflower is the most sensitive of the cole...

Page 1: COLE CROPS - College of Agriculture & Natural …...Cauliflower is the most sensitive of the cole crops to adverse weather. Mature cauliflower plants can withstand temperatures as

Cooperative Extension Service • Michigan State University • Extension Bulletin E-1591 (Revision) • June 1988 60$

COMMERCIAL VEGETABLE RECOMMENDATIONS

COLE CROPSBroccoli, Brussels Sprouts, Cabbage, Cauliflower

Bernard H. Zandstra, Department of HorticultureChristine T. Stephens, Department of Botany and Plant Pathology

Edward J. Graf his, Department of Entomology

This bulletin has been prepared as a guide forcommercial production of the cole crops. The

cole crops are members of the Cruciferae (mustard)family, which also includes Chinese cabbage, col-lard, horseradish, kale, kohlrabi, mustard, radish,rutabaga, turnip, and watercress. The term "cole"probably originated in ancient Roman times as aname for leafy vegetables in the mustard family,but now we use it primarily for broccoli, Brusselssprouts, cabbage, and cauliflower. They are impor-tant fresh market and processing crops in Michi-gan, with a combined total of about 7,000 acresgrown each year.

ProductionThe yield figures (Table 1) are based on the

experience of Michigan growers over many years.Experienced growers should be able to producecole crops at good or higher yield levels regularly.

Types and cultivarsBroccoli, Brussels sprouts, cabbage, and cauli-

flower are all botanical varieties of the genus andspecies Brassica oleracea. Because they are closelyrelated, their culture is similar. However, there areimportant differences both between and withinthe botanical varieties.

BROCCOLI: Most broccoli cultivars producegood quality heads during cool weather, but onlya few are productive at temperatures above 85° F.By selecting cultivars adapted to different environ-mental conditions, it is possible to produce goodbroccoli from June through October in Michigan.

Broccoli plants produce large central heads. Afterthe main heads are cut, the plants produce side-shoots in the axils of the leaves. Most older culti-vars produce many sideshoots, but most recently-developed cultivars produce very few sideshoots.Some new cultivars produce heads on an elon-gated stem, so that the heads are exposed at thetop of the plant. These heads are easier to cut andbunch than heads on short stalks, and they areless susceptible to diseases caused by contact withsurrounding leaves.

Other characteristics to consider when choos-ing a broccoli cultivar are bead size, head uniform-ity, color, firmness, and days to maturity.

BRUSSELS SPROUTS: Brussels sproutsrequire a long, cool growing season to producegood quality buds. Most areas in Michigan are not

Table 1. Yields of

Broccoli(main heads)

Brussels sprouts(buds)

Cabbage,fresh market

Cabbage,processing

Cauliflower

cole

\Low

2.5

4

10

254

crops in Michigan

'ields—Tons per acre

Good

4

5

15

307

Excellent

5

6

20

4010

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well-suited to Brussels sprout production becausesummers are too hot, and the cool, fall growingseason is too short for efficient production.

There are two basic types of Brussels sproutcultivars: short or dwarf types that are very com-pact with no space between sprouts on the stalks;and tall or standard types. The short types maturesooner and are more suited to production inMichigan.

CABBAGE: There are several types of cab-bage, including white or green, red, and savoy.There are several head shapes, the most commonbeing round, flat, and oval. Early-maturing cab-bage cultivars are very compact and grow rapidly.Mid- and late-maturing cultivars are larger, andheads can be harvested early for market, or laterfor processing. Some late-maturing cultivars canbe stored for several months and marketed duringthe winter.

CAULIFLOWER: The main differencesbetween cauliflower cultivars center aroundmaturity. Early-maturing cultivars tend to besmaller, are not self-blanching, have lighter heads,and are usually more susceptible to environmen-tal stress. Mid-season and late-maturity cultivarsgrow larger, many are self blanching, and theheads are larger and more dense.

Some recent mid- and late-season cultivarshave a more compact growth habit than tradi-tional cultivars. Heads are borne on a taller stalkand leaves are smaller. These cultivars may beplanted at a closer spacing than larger plants, butrequire more careful management in the field.

Climate and IrrigationAll of the cole crops are cool-season crops.

They grow well under moderate temperatures andwithstand moderate frosts. Cole crop seeds willgerminate at 40° F, but germinate best at 70 to75° F. Of the cole crops, cabbage is the least sus-ceptible to high temperatures. It grows and pro-duces well at temperatures up to 85° F. Brusselssprouts grow well at temperatures below 70° Fand are grown commercially in areas with coolsummers or mild winters. Broccoli and cauliflowergrow well at temperatures of 70 to 85° F, butheads tend to be soft and become over-mature

quickly at temperatures over 80° F. Cauliflower isusually grown as a fall crop in Michigan to avoidhot summer temperatures.

Cauliflower is the most sensitive of the colecrops to adverse weather. Mature cauliflowerplants can withstand temperatures as low as 25° Ffor several hours late in the fall without damage tothe curd. However, young plants subjected tofreezing temperatures often "button" (form headsprematurely). Cauliflower heads maturing duringwarm weather (above 80° F) often suffer from oneor more disorders: leafy heads, riciness (overmature florets), purple or green color, soft, looseheads, and poor wrapper leaf development.

Cole crop roots penetrate the soil to a depthof only 18 to 24 inches. They have a relatively highand constant moisture requirement. Thus, evenmoderate drought stress any time during thegrowing season may cause significant reductionsin growth and yield. Growth during dry periodscauses internal tipburn in cabbage and buttoningand tipburn in cauliflower. Cole crops require 1 to2 acre inches of water as rainfall or irrigation perweek, depending on plant size, stage of growthand soil type.

Irrigate cole crops with Vi inch of waterimmediately after transplanting to avoid moisturestress on young plants. If the soil is dry at thetime of transplanting, irrigate the land to beplanted 2 days before transplanting with lh to1 inch of water, and follow the transplanting withVi inch of water.

Cole crops are also very sensitive to water-logged soil. If the roots are under water for over24 hours, many plants will die. Therefore, plantcole crops only on soil with good surface and sub-surface drainage.

Soils and Field PreparationCole crops grow well on well-drained soils

with good moisture-holding capacity. They arevery sensitive to nutrient deficiencies and low pH.Loams, clay loams, and muck soils are ideal forcole crop production, but lighter soils can alsoproduce good cole crops if managed carefully.Because of potential disease problems, use a croprotation that does not include members of the

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Cruciferae family more than 1 year in 3. Eliminateweeds in the Cruciferae family, such as wild mus-tard, yellow rocket, shepherdspurse, and wildradish since they serve as hosts for several colecrop diseases.

Prepare the field for transplanting by broad-casting the fertilizer and incorporating the herbi-cide and boron. A slightly rough soil surface willhelp reduce sand movement and blasting of thetransplants. If preparing the field for direct seed-ing, make a smoother seedbed. Cole crops nor-mally germinate and emerge easily unless a hardcrust forms on the soil surface.

FertilizerThe cole crops require careful nutrient

management to obtain good quality and maxi-mum yields. They are sensitive to several micro-nutrient deficiencies and require nitrogenthroughout the growing season. Maintain the soilpH at 6.2 to 6.8 on mineral soils and 5.5 or higheron organic soils. Add lime as recommended byyour soil test to achieve the desired pH level.

Cole crops require moderate to high amountsof nitrogen, phosphorus, and potassium. As abasis for good nutrient management, maintain soiltest levels of phosphate (P2O5) at 150 to 200 lb peracre and of potash (K2O) at 300 to 350 lb per acre.Each year add a minimum of 120 lb P2O5 and120 lb K2O. Total nitrogen (N) rates will vary withcrop and cultivar, but all require at least 150 lb Nper acre.

To prepare fields for planting, broadcast andplow down or disc in 60 lb N, 120 lb P2O5, and120 lb K2O. Sidedress all crops with 50 lb N 3weeks and 6 weeks after transplanting. Apply athird sidedressing of 50 lb N to cauliflower andBrussels sprouts. Sidedress with ammoniumnitrate (33-0-0) or urea-ammonium nitrate 28 per-cent N solution if they are available. Urea (45-0-0)is a good source of N, but it has to be incorporatedinto the soil to avoid volatilization and is slowerreacting than ammonium nitrate. It should beused for the final sidedressing to extend N avail-ability in light soils.

Secondary and MicronutrientsThe cole crops are sensitive to deficiencies

of calcium, magnesium, manganese, boron, andmolybdenum.

Calcium (Ca) deficiency within the plantcauses internal tipburn of cabbage and externaltipburn of cabbage, cauliflower, and Brusselssprouts. There is sufficient calcium for plantgrowth and development in most soils. However,during hot, dry weather plants grow rapidly andsufficient calcium does not reach the developingleaf tips, which subsequently die. Calcium is notreadily available to plants at soil pH below 6.0,and young cole crop plants growing at low pHoften demonstrate calcium deficiency symptomsof poorly developed leaves with dead margins,especially during cool weather. Maintain soil pHabove 6.5 to reduce incidence of calciumdeficiency.

Magnesium (Mg) deficiency occurs in cab-bage and cauliflower plants when they are grownon low-pH soils. Magnesium is a very mobile ele-ment and is transported within the plants fromolder to newly-formed leaves when it is deficient.The older leaves of deficient plants becomemottled and yellow. Younger leaves remain anormal green color.

When a soil test indicates a low magnesiumlevel and a need for lime, apply finely grounddolomitic limestone. If magnesium deficiencyoccurs during the growing season, apply 2 lbactual magnesium as 20 lb magnesium sulfate(epsom salts) per acre in a foliar spray, includinga surfactant. Repeat after 10 days if symptomspersist.

Boron (B) deficiency occurs to some extent inall the cole crops, but is a major problem in cauli-flower, causing hollow stem and brown, water-soaked spots on the head. Hollow stem alsooccurs in cabbage and broccoli. Most forms ofboron are very soluble and leach from the soilrapidly. There is very little chance of boron toxic-ity to sensitive crops as a result of carryover.However, if boron is applied in the spring withanticipation of planting cole crops, there may besufficient boron in the soil to adversely affectsmall grains, beans, peas, and cucumbers planted

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there the same growing season.

Apply boron to all land to be planted to colecrops. To avoid boron deficiency, apply 3 to 4 lb ofactual boron per acre (30 to 40 lb borax or 15 to20 lb Solubor) and disc in before planting. Boraxcan be mixed with granular fertilizer and broad-cast on the field. Solubor can be sprayed on thesoil and incorporated with the herbicide. Boroncan also be applied to foliage, but it is less effec-tive than soil application. If additional boron isneeded during the season, apply 0.3 lb actualboron per acre (1.5 lb Solubor) in 30 gallons ofwater as a foliar spray.

Manganese (Mn) deficiency in cole crops issimilar in appearance to magnesium deficiency,but yellowing is more general over the wholeplant. Interveinal areas turn pale-green tomottled-yellow, while veins remain dark green.The deficiency frequently occurs at soil pH above7.0. At pH below 5.5, manganese toxicity mayoccur, with symptoms similar to the deficiency.Maintain pH above 6.0 to avoid manganese toxic-ity. Broadcast soil applications of manganese arerelatively inefficient in solving manganese defi-ciency because of its high fixation and immobilityin the soil.

When a soil test or previous experience indi-cates that manganese is deficient, apply 8 to 12 lbof manganese per acre (30 to 45 lb manganesesulfate) in a band 2 inches below the seed or as asidedressing after plants are established. For foliarapplication, apply 1 to 2 lb manganese (4 to 8 lbmanganese sulfate) in a foliar spray 3 to 4 weeksafter transplanting, or when plants are about6 inches high after seeding. Reapply every 2weeks until symptoms disappear.

Molybdenum (Mo) deficiency occurs occa-sionally in cole crops, primarily on low-pH soils.Cauliflower is very susceptible. Recently maturedleaves of molybdenum-deficient plants are lightgreen or slightly yellow. Leaf margins may curl inand die. Some leaves may not expand fully, caus-ing a condition called whiptail.

If the deficiency occurs in the field, apply3 ounces of sodium molybdate per acre as a foliarspray that includes a surfactant. One or twoapplications should overcome the deficiency.

Transplant ProductionCole crop transplants can be grown in the

greenhouse or field. Plants for transplanting intothe field during April and May are grown in thegreenhouse. Plants for later field establishmentcan be grown in the greenhouse or field seedbeds.Many of the cabbage and broccoli plants trans-planted during April and May in Michigan aregrown in field seedbeds in the southern UnitedStates and shipped north by truck.

Greenhouse Plant Production: Grow cole croptransplants in % to 1 inch diameter cells. Twohundred or 288 square-cell greenhouse flats (11 by22 inches) are ideal for cole crop plant production.Plants grown in smaller cells require more carefulwatering and fertilizing and often become spindlyand root bound. Early cauliflower plants are verysensitive to root binding and often button if heldin cells too long.

Use a moderately coarse, pasteurized soil orartificial mix that is well drained but holds somemoisture. Soak the media thoroughly at least oneday before seeding. Sow seeds about lk inch deep,and water after seeding. After seedlings haveemerged, water daily or as needed; soak the cellscompletely, but do not overwater. Do not usesprinkler or mist systems that keep the leaves andmedia wet continuously.

After the first true leaves appear, water onceor twice a week with 100 ppm of a soluble com-plete fertilizer (such as 20-20-20). Do not over-fertilize or plants will become tall and thin. Colecrop seeds germinate rapidly at temperaturesabove 60° F. After emergence, maintain 60 to 65° Fnight and 70 to 75° F day temperatures.

Cole crop plants are ready for transplanting4 to 5 weeks after seeding, when they are 4 to 6inches tall with 3 to 4 true leaves. If the plants areready but cannot be transplanted immediately,reduce water and temperature slightly to slowtheir growth. Cole crop plants should not be hard-ened before transplanting during cool weather. Ifthey will be transplanted during hot, dry weather,harden the plants for 2 or 3 days before trans-planting by exposing them to ambient conditionswhile still in flats. The day before transplanting,water the plants with a complete fertilizer solu-

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tion. Soak the media thoroughly with water beforetaking the plants to the field.

Transplant Production in Field Seedbeds:Establish field seedbeds on light, sandy soil thathas not had cole crops on it during the preceding3 years. Before seeding, disc in 300 lb 12-12-12 orthe equivalent per acre. Sow 3 to 4 seeds per inchlA to Vi inch deep in moist soil in rows 10 to 12inches apart. Three to four ounces of seed willprovide enough plants for one acre of field trans-planting. Be sure to apply an herbicide, eitherpreplant incorporated or after seeding.

After sowing the seed, drench the soil witha soil insecticide to avoid maggot and cutwormdamage. Irrigate the seedbed regularly so thatplants do not suffer moisture stress. Sow cabbageand broccoli seeds in early April to have plantsready for transplanting in May and thereafter.Sow seeds every week to maintain a constantsupply of young plants. Sow Brussels sprouts inlate May for transplanting in early July. Cauli-flower seedlings are sensitive to cool weather andfrost and should not be sown in the field beforeMay 1. Sow cauliflower seed May 15 to 30 forplants for the fall harvest.

Soak the seedbed, or loosen the soil aroundthe plants with a fork before pulling to keep rootsystems intact. It is best to pull the plants neededeach day. However, if more plants are ready thancan be planted immediately, pull and pack themloosely in boxes, and store at 50° F for up to 1week. Make sure plants are dry before packing inboxes to prevent disease development.

Field grown plants are ready for transplantingwhen they have 3 to 4 leaves and are 5 to 6 inchestall. They are usually ready 5 to 6 weeks aftersowing, but early plantings may take 1 or 2 weekslonger. Plants older than 6 weeks can be trans-planted, but they become established slowly,suffer higher mortality, and are more likelyto button.

Spacing and PlantingThe recommended planting dates and spac-

ings for cole crops are given in Table 2. Cole cropseeds vary considerably in size, with 4,000 to12,000 seeds per ounce. At a 3 ft by 1 ft field spac-ing, there are about 15,000 plants per acre; at a 3 ftby Vh ft spacing, there are about 10,000 plants peracre.

Cole crops are usually transplanted in Michi-gan. To help plants become established in coolsoil, include a high-phosphorus starter fertilizer inthe transplant water. Apply 2 to 4 fl. oz. of waterwith each plant. Use the higher rate when soil isdry. Also include an insecticide for maggot controlin the transplant water, or drench the plants witha soil insecticide after transplanting.

Cole crops can be established relatively easilyby direct seeding. The seeds germinate and plantsemerge quickly, even in cool soils. The seeds areround and thus are well adapted to precisionseeding. Seeded cole crops normally take 20 to30 days longer from planting to harvest than thesame transplanted crop. A precision seeder isessential for direct seeding of cole crops. Belt, cup,

Table 2. Planting dates and final spacing for direct-seeded and transplanted cole crops

CropEstablishment

methodPlanting

dateRow spacing

(inches)Plant spacing

(inches)

Broccoli

Brussels sprouts

Cabbage

Cauliflower

Transplanted

Seeded

Transplanted

Transplanted

Seeded

Transplanted

4/15-7/15

4/15-7/15

6/20-7/10

4/1-7/15

4/15-6/15

6/20-7/10

24-36

20-36

36

30-36

30-36

36-40

12

6-8

24

12-18

12-20

18-24

Seeded 5/15-5/30 36-40 16-24

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and vacuum planters can plant uncoated seed.Since seed size varies considerably between cul-tivars, several different belts or cups will beneeded to plant different crops and cultivars.Clean seed is essential for vacuum plantersbecause seed trash blocks the small plate holes,causing skips in the row.

To obtain a uniform stand, make sure theseeder singulates the seed. Plant double or triplethe desired stand, and thin with a hoe 2 to 3weeks after emergence. If saving time is moreimportant than a perfect stand, plant to thedesired stand. You should be able to obtain aboutan 80% stand by seeding cabbage and broccoli tostand. Cauliflower should always be plantedthicker and thinned to stand because there arefewer total plants per acre, and stand reductionsthus have a greater impact on potential yield.

Harvest and PostharvestEach of the cole crops has different harvest

and postharvest requirements. Broccoli is readyfor harvest 45 to 60 days after transplanting, or60 to 75 days after direct seeding. Hybrid cultivarsmature very uniformly and most heads in a plant-ing can be harvested in two trips over the fieldwithin 7 days. Some older cultivars mature over alonger period of time and may require three tofour harvests to cut over 90% of the main heads.Some cultivars produce sideshoots for 4 to 6weeks after initial harvest. The sideshoots becomeprogressively smaller, and it usually does not payto harvest them after the main heads have beencut. They may be a good source of broccoli forU-pick operations.

Cut broccoli by hand and transport it to apacking shed in containers or in bulk wagons.Harvest broccoli heads that are 3 to 6 inches indiameter and have a uniform green color. Cut theheads so that the total length from the top of thehead to the end of the stem is 6 to 8 inches. Striplarge leaves off the harvested stems.

The size of broccoli heads is directly related toplant spacing: the closer the spacing the smallerthe heads. Broccoli is usually sold in 6- to 7-inchdiameter bunches containing 1, 2 or 3 heads. Tiethe bunches with paper-covered wire, rubber, or

plastic bands, and pack 14 or 18 bunches in 23-lbbroccoli boxes.

No. 1 broccoli is solid with no open florets; ithas uniform green or blue-green color; the headsare clean and contain no insects, soft rot, or hol-low stem, with few or no leaves in the heads.

Harvest broccoli early in the morning so thatthe heads remain cool. Pack, hydrocool, ice it, andplace in a cold storage at 32° F as soon as possible.If broccoli is kept iced at 32° F and 95% relativehumidity, it should remain in good condition for3 to 4 weeks.

Brussels sprouts mature 90 to 120 days aftertransplanting. When sprouts at the bottom of thestalk are 3A to 1 inch in diameter, cut off the topof the plant so that no more sprouts form. Thesprouts that have developed will then fill out andmature in about 4 weeks. Remove leaves with aknife or machete before harvesting the stalks.Harvest the stalks by chopping them off atground level. The stalks may be sold with sproutsattached (for local sales), or the sprouts can beremoved and packed in small baskets.

Cabbage matures 60 to 80 days after trans-planting. It is mature when heads are solid. Har-vest early cultivars soon after they reach maturityto prevent the heads from splitting. Most full-season cultivars are less susceptible to splittingand continue to gain size until harvested. Cutcabbage for market with 4 or 5 wrapper leaves.No. 1 heads for market weigh 2 to 5 lb. An idealsize is 2Vi to 3 lb so that 20 heads will fill a 55 lb,1%-bushel box or wirebound crate.

No. 1 heads are solid, have uniform greencolor, no insect injury or debris, no soft rot orblack rot, no thrips damage, and no internaltipburn.

Cabbage stores well and should last 4 to 6weeks at 32° F and 95% relative humidity. Somelate-maturing cultivars store well for 5 to 6months and can be marketed during the winter.

Depending on the cultivar and season, cauli-flower matures 50 to 90 days after transplanting.Cauliflower is ready for harvest when heads are6 to 8 inches in diameter. Cut the heads before

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they become overmature and florets begin toseparate.

Most cauliflower needs to be blanched toproduce uniformly white heads. Blanching is anyprocess that prevents sunlight from contactingthe heads and turning them yellow. Mostrecently-developed, late-season cultivars aremoderately to very self-blanching; i.e., wrapperleaves naturally curl over and cover the heads sothat sunlight doesn't penetrate, making tyingunnecessary. Self-blanching occurs most effec-tively after September 1 when night temperaturesfall below 50° F. At higher temperatures thewrapper leaves do not cover the heads well andthe plants have to be tied. Cauliflower that doesnot require blanching is being developed andshould be on the market soon.

Tying is the traditional method of blanchingcauliflower. When plants are nearing maturity,check fields every 3 or 4 days for visible whiteheads. Gather the outer leaves together over theheads and tie them together with colored rubberbands or twine, so that sunlight cannot penetrateto the head. Repeat the process twice a week,tying all the visible heads on a day with the samecolor band. Use a different color each day. Tie theleaves together as high as possible to allow airmovement over the heads to avoid head rots.

Cauliflower heads mature 7 to 14 days aftertying, depending on temperature. One week aftertying, check several heads to determine if theyhave reached the desired size. When 75% or moreare large enough, harvest all the heads tied withthat color band. Some small heads will be har-vested, but since some plants produce small headswhich do not reach marketable size, little totalyield will be lost. Cauliflower heads become over-mature quickly when temperatures are above 70° F.

Cut cauliflower by hand with the leavesintact and transport the heads to a packing shed.Remove most of the leaves and trim the butt."Michigan pack" cauliflower is the most commonpacking system in Michigan. Four to six leaves areleft attached to the butt and trimmed 2 or 3 inchesabove the top of the head. The heads are packed12 or 16 to a 2-layer box. In the western pack, fourto six leaves are left attached to the butt, but aretrimmed back to the base of the head. The heads

are then wrapped in cellophane and packed 9,12,or 16 to a single-layer box.

No. 1 cauliflower heads are uniformly whiteor cream color, 4 to 8 inches in diameter, solid,with no insect damage or debris, no soft rot, nospots or discoloration, and no hollow stem, rici-ness or leaves in the heads and weigh 2 to 3 lbeach. Some late-maturing cultivars produce headsthat remain solid up to 6 lb. Heads this size maybe used for processing or local sales but are gener-ally too large for fresh market.

If cauliflower is refrigerated soon after har-vest, it can be stored for 2 to 3 weeks at 32° F and98% relative humidity. Hydrocooling will improvestorability and extend storage life. Handle cauli-flower heads carefully because they are suscep-tible to bruising and abrasion and spots turnbrown soon after contact with other heads or thecontainer.

Physiological DisordersHollow stem occurs in cauliflower, broccoli,

and cabbage. It is primarily a result of boron defi-ciency, but may be influenced by excessive nitro-gen fertilizer application and rapid growth. Borondeficiency may appear as brown water-soakedspots on cauliflower heads, but often there are noexternal symptoms of hollow stem. In seriouscases, the hollow stem proceeds upward throughthe surface of the head and the internal surface ofthe cavity becomes brown or black. Bacterial softrot may develop, causing a soft, odoriferous rot ofthe head surface and the internal cavity. Somecauliflower cultivars are more susceptible to hol-low stem than others. It is difficult to avoid hollowstem completely, especially during the summer. Itis less of a problem in the fall when plants matureslowly. Use of resistant cultivars, maintenanceof correct soil pH, irrigation, application of boronand sufficient but not excess N-P-K reduces theproblem.

Brown spotting of the heads is sometimescaused by drops of moisture which are exudedfrom the leaf tips, usually at night. This process iscalled guttation. The water contains dissolvedsalts that kill cells on the surface of the heads,leaving small brown spots. It is especially a prob-

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lem in low, foggy areas where the heads remainwet much of the day and the guttation water doesnot evaporate quickly. The brown spots make theheads unattractive but usually do not cause rots.

Riciness is sometimes a problem in maturecauliflower. Individual florets develop and elon-gate, causing them to look like grains of rice. Inextreme cases, the floral parts may extend lk inchabove the head and turn green. Riciness oftenoccurs as cauliflower reaches and passes maturity.It is affected by adverse environment, especiallyhigh temperature conditions. Some cultivars aremuch more susceptible than others. When ricinesshas been a recurring problem, use other cultivars.

Buttoning is premature heading of cauli-flower. Any heading that occurs before the planthas attained sufficient vegetative growth to sup-port production of a marketable head is called but-toning. It is caused by stress on young plants,especially during the first 8 weeks of growth. Themost common causes of buttoning are: exposureof young transplants to frost for 4 or more hours;exposure of young plants to temperatures below50° F for 5 or more consecutive days in the field;use of overhardened, rootbound, or old (over 6weeks) transplants; excessively wet or dry condi-tions, especially immediately after transplanting;inadequate fertilizer, especially nitrogen; andinsect, disease, or weed pressure that severelyreduces vegetative growth. Early maturing culti-vars are more susceptible to buttoning than later-maturing cultivars. To avoid buttoning, do notexpose transplants to low temperatures, plantonly young, vigorous plants in the field, irrigateafter transplanting, maintain recommended soilpH and nutrition levels, control pests, and usefull-season cultivars.

Blindness is a condition in cauliflower inwhich the growing point dies at an early stage ofgrowth but the plant remains alive. A long, nar-row leaf often develops at the apex, which some-times causes this disorder to be confused withwhiptail, caused by molybdenum deficiency. Theother leaves become thicker and darker greenthan normal. The plants do not develop heads.The exact cause of blindness is not known. Expo-sure of young plants to frost may kill the growingpoint. However, it often occurs in summer-planted

cauliflower that has not been exposed to frost.Insects may also damage the growing point,inducing blindness. Some cultivars are moresusceptible than others.

Tipburn: In cabbage, tips of individual leavesinside the head turn brown. There may be one orseveral leaves with dead tips. The affected leavesdevelop during periods of rapid growth of theplant, usually during warm weather with moisturestress. Apparently, sufficient calcium for normalcell development does not reach the leaf tips.Internal tipburn is only visible by cutting headsopen. The discolored leaves make the affectedheads unacceptable for fresh market or process-ing. Some cultivars are more susceptible thanothers.

In cauliflower, tips or margins of young andrecently-developed leaves die and soft rot oftendevelops. The problem usually occurs as theheads begin to form. The rotting leaf tips oftenstain the heads and sometimes the soft rotspreads to the heads. The problem is more com-mon on light, sandy soils, and during warm grow-ing conditions. Some cultivars are very suscep-tible. Tipburn cannot be avoided completely. Toreduce its incidence, use cultivars which are lesssusceptible. Grow the crops on soils that containsufficient organic matter or clay and irrigate regu-larly to maintain a constant supply of moisture forthe plants. Apply nitrogen at adequate levels.

InsectsSee Extension Bulletin E-968, Cole Crop Insect

Pests, for pictures and detailed descriptions ofinsects. See Extension Bulletin E-312, Control ofInsects, Diseases, and Nematodes on Commercial Vege-tables, for current pest control recommendations.

Cabbage maggot (Delia brassicae) is a seriouspest of early direct-seeded or transplanted colecrops. The adult flies emerge from the soil in earlyMay and lay their eggs on cole crop plants andrelated weeds near the soil surface or in the soil atthe base of the plants. The short 0/4 inch), whitemaggots emerge a few days later and begin to eatand burrow into the plant stems and roots. Youngplants that are invaded by maggots usually wiltand die.

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There are three generations of cabbage mag-got each year. The first generation does the mostdamage because it emerges when transplants andseedlings are small. Later generations do lessdamage because many are killed by high soiltemperatures and the crops are advanced enoughto withstand some injury. Protect transplantedcole crops with a soil insecticide either in thetransplant water or as a drench after transplant-ing. Treat direct-seeded plantings and seedbedsbefore seeding or with a drench over the rowsafter seeding.

Imported cabbage worm (Pieris rapae) adults,the white butterflies often seen around crucifer-ous crops, emerge from the pupal stage in earlyMay and lay their eggs on cole crops and othercruciferous crops and weeds. The velvety greenworms, which grow to over one inch in length, eatholes in leaves and leave large amounts of greendebris on the leaves. There are several generationsa year, and the adults and larvae may be activeuntil frost.

Observe fields for adult activity and checkplants for eggs and larvae. Treat cabbage with aninsecticide as soon as the insects appear. Broccoliand cauliflower can tolerate some injury prior tohead formation, but should be treated duringhead formation to avoid insect contamination ofthe harvested product.

Cabbage looper (Trichoplusia ni) adultsmigrate into Michigan during July and August.The adults are about 1 to IV2 inches across, gray-brown, and fly and lay eggs mostly at night. Thelarvae are light green, with a white stripe on eachside, about 1 inch long, and move by humpingtheir back like an inch-worm, from which they gettheir name "looper." There may be 2 or 3 genera-tions per year. As the larvae grow, they becomemore difficult to control. Plant damage and prod-uct contamination are similar to that of importedcabbage worm.

Monitor fields regularly for eggs, larvae, anddamage. Apply insecticides as needed for control.Cabbage loopers are much more tolerant of insec-ticides than imported cabbage worms. Be sure ofyour identification and use higher rates or moretoxic materials on loopers.

Diamondback moth (Plutella maculipennis)does not do major damage but is often seen inMichigan. The gray adults overwinter on trash inthe field, lay eggs in the spring, and the small(1/3 inch) yellow-green larvae emerge soon there-after. The worms eat numerous small holes in theleaves. They leave a few small webs in the centerof the plant. Control of diamondback moth issimilar to that for other worms.

Thrips (Thrips tabaci) are very small (1/16inch), yellow or brown insects that damage colecrops by rasping the leaf surface and sucking thesap. They cause economic injury primarily oncabbage, where they live and eat inside severallayers of leaves. Injury looks like rust spots on theinner leaves. Large areas of leaves can be affectedduring heavy infestations. Badly infested headsare not usable for fresh market or processing.Thrips damage usually increases during the hot,dry weather of late summer. Once thrips areinside cabbage heads, it is very difficult to controlthem. High pressure sprays for worm controldirected down into the heads will give somethrips control. If thrips are present, begin insecti-cide application as soon as heads begin to form.

Cabbage aphids are small (1/16 inch), blue-gray insects that suck sap from the plants. Theyare generally most abundant from mid-summerthrough October. Heavy infestations cause leavesto cup and curl inward. Aphids live in the outerleaves of cabbage, and the presence of live ordead ones makes the cabbage unmarketable.Aphids can be controlled relatively easily withinsecticides.

DiseasesRhizoctonia solani causes a number of

closely-related diseases of cole crops, includingdamping of£ wirestem, bottom rot, and head rot.If the fungus attacks very young seedlings, thedisease is called damping off. The fungus pene-trates seedlings near the soil line causing water-soaked constrictions of the stem, which girdle theplant. The plants then wilt and topple over. Ifplants survive the initial attack, the center of thestem decays while the outer stalk provides suffi-cient support to keep the plants erect. At thisstage the disease is called wirestem. Stems are

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brown or black and wiry above the soil line. Theplants grow very slowly and usually do notdevelop to maturity. Bottom rot occurs as a carry-over from wirestem. Lower leaves wilt, rot anddarken, but remain on the plant. Head rot maydevelop, causing a darkening and decaying of thestem at the base of the heads and spotting andwilting of the leaves in the center of the head.

Control damping off and wirestem in thegreenhouse and field seedbeds by using sanitizedmedia and containers, treating seed or soil with afungicide, and avoiding overwatering. Do notgrow cole crops in low-lying fields with heavysoils, and do not use diseased transplants.

Black rot (Xanthomonas campestris pv. campestris)is a bacterial disease that affects all the cole crops.Cotyledons on infected plants become watersoaked and then shrivel and drop off. On trueleaves, the infection generally appears as a yellowv-shaped area along the leaf margin. As thelesions enlarge, the leaf veins within them turnblack. Numerous brown specks appear in yellowareas on the leaf surface. The pathogen movesthrough the leaf into the water-conducting (vascu-lar) system, causing a blackening and a pluggingof the veins. Early infections usually cause plantwilting and death. Later infections cause stunting,smaller heads, or possibly only leaf spotting.

Under conditions favorable for black rotdevelopment (80 to 86° F and high humidity), thedisease moves rapidly through infected plants andspreads to adjoining plants in wind and rain. Theblack rot organism overwinters on crop debris inthe field, but infection occurs more often frominfected seed. To avoid black rot, use seed that hasbeen hotwater-treated or assayed and found to becompletely free of black rot. Rotate fields out ofcole crops for at least 2 years to avoid reinfestationin the field. Copper sprays applied with a boomsprayer may reduce spread of the organism in thefield. Do not use an airblast sprayer, because itwill increase spread of the pathogen.

Club root (Plasmodiophora brassicae) is a fungaldisease that attacks the roots of all cole crops andother cruciferous crops and weeds. Infected plantswilt in the middle of hot, sunny days, and leavesturn pale green to yellow. Eventually, infected

plants wilt permanently and die, or survive in astunted condition.

Swimming spores of the pathogen enter rootsthrough root hairs or wounds. The organismstimulates plant cell multiplication, causing rootsto enlarge and form spindle-shaped galls or"clubs." The growth of the clubs inhibits devel-opment of a normal root system and blocks thevascular system. The clubbed roots eventuallydecay and are invaded by soft rot bacteria whichrelease a toxin. Lack of sufficient water and thepresence of the toxin causes foliar wilting.

Clubroot incidence can be reduced by usinguninfected transplants, avoiding movement ofmachinery from infested areas into clean fields,and maintaining soil pH of 7.3 or higher. Croprotation is not very effective because the restingspores can survive in the soil for many years.

Downy mildew (Peronospora parasitica). Theinitial symptom of this fungal disease is theappearance of small, irregularly shaped grayish-purple spots on stems and the undersides ofleaves. Under cool, moist conditions, the spotsenlarge and become covered with fluffy, grayish-white mycelia. The upper leaf surface turns yellowand dries out. Heavily infected leaves eventuallydrop of £ The organism may move systemically inthe plant causing internal darkening of broccoli,cabbage, and cauliflower heads. Downy mildewoverwinters in plant debris or on cruciferous weedhosts. It spreads in the field with splashing waterduring cool weather, and is primarily a problemduring the fall. Fungicide applications help pre-vent spread of the organism in the field.

Blackleg (Phoma lingam) is most common oncabbage, but it also affects other cole crops. Symp-toms may appear early in the growing seasonon seedlings not yet transplanted in the field.Inconspicuous, small, circular, dark lesions appearon the leaves of the infected plants. The spotsgradually enlarge, becoming well defined with agray center filled with numerous black, pimple-like, spore-bearing structures called pycnidia. Thelesions on stems are oval shaped and often sur-rounded by a purplish margin. Spots spread overthe whole plant including the root system. Thedark cankers which form on affected roots may

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eventually destroy the fibrous root system. Thedisease causes wilting, stunting and death ofaffected plants. To avoid blackleg, use disease-freeseed and rotate fields out of cole crops for at leastthree years.

Alternaria spp. fungi cause leaf spotting andhead rotting of crucifers. The initial disease symp-tom is the appearance of small dark spots on olderleaves. The spots are generally circular, rangingfrom Vi to IV2 inches in diameter. A brown or blackvelvety mold, composed of masses of fungalspores, rapidly covers the lesion. These spores ruboff the lesion surface easily. Lesions may coalesceto form large, irregular, diseased areas on the leafsurface. Cabbage leaf margins are often colonizedby Alternaria spp. after tipburn or other injuries tothe plant. Bacterial soft rot often follows Alternariainfection. On cauliflower, tiny brown sunkenlesions appear on the curds. On broccoli heads thelesions are yellow. The spots enlarge rapidly andare eventually covered with black spores.

To avoid Alternaria diseases, use high quality,disease-free seed; irrigate early in the day so thatleaves dry rapidly; and tie cauliflower leaves ashigh as possible to allow air movement and toreduce free moisture on the head. Apply fungi-cides when necessary.

Soft rot (Erwinia carotovora) bacteria cause awatery, soft, foul-smelling rot of the cole crops.Bacterial infection often occurs after chemical,mechanical, pest, or other injury. It often followsexternal or internal tipburn. The bacteria softenthe cell walls of plant tissue, which results in arapid collapse into a slimy mess. Soft rot may be aprimary pathogen on broccoli heads, especiallyduring warm, humid weather. The bacteriabecome established in small droplets of water thatremain on the heads. Cultivars with domed headsthat shed surface water are less susceptible. Toavoid soft rot, grow cole crops on well-drainedsoils and maintain adequate soil moisture to avoidtipburn. Select cultivars recommended for Michi-gan, and avoid injury to plants.

Turnip mosaic virus and cauliflower mosaicvirus sometimes cause economic losses in storedcabbage. Early infection in the field causes leafspotting and leaf drop. The spots become black

and sunken on inner cabbage leaves during long-term storage. Turnip mosaic spots are larger thancauliflower mosaic spots. The viruses are trans-mitted by aphids. Aphid control is the primarymeans of virus control. Where the viruses havebeen a problem, make an extra effort to controlcruciferous weeds near seed beds. Select cabbagecultivars that are resistant to virus infection.

Additional InformationMore information on cole crop production is

contained in the following bulletins which areavailable from county Cooperative ExtensionService offices or from the MSU Bulletin Office,P.O. Box 6640, East Lansing, MI 48826-6640.

E-312, Control of Insects, Diseases, and Nematodes onCommercial Vegetables

E-433, Weed Control Guide for Vegetable Crops

E-486, Secondary and Micronutrients for Vegetables andField Crops

E-550, Fertilizer Recommendations for Vegetable andField Crops in Michigan

E-675, Vegetable Varieties for Commercial Growers

E-968, Cole Crop Insect Pests

E-1565, Yields of Michigan Vegetable Crops

E-1668, Disorders of Cole Crops

E-1751, Identifying Diseases of Vegetables

E-1998, Costs of Producing Broccoli in WesternMichigan

E-2003, Costs of Producing Cauliflower in WesternMichigan

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Issued in furtherance of Cooperative Extension work in agriculture and home economics, acts of May 8, and June 30. 1914, in cooperation with theU.S. Department of Agriculture. W.J. Moline, Director, Cooperative Extension Service, Michigan State University, E. Lansing, Ml 48824.

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File 26.52 (vegetables-commercial).