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Temperature

• Plant processes influenced:– Photosynthesis– Respiration– Enzyme activity – Transpiration– Stomatal opening– Pollination – Seed germination

TemperatureTemperature

• This factor, more than any other, This factor, more than any other, determines what plants can be grown in a determines what plants can be grown in a particular areaparticular area

TemperatureTemperature

• Temperature affects the maturity rate of Temperature affects the maturity rate of garden productsgarden products

TemperatureTemperature

• Temperature can influence some diseases Temperature can influence some diseases and insect problemsand insect problems

• Temperature influences quality of most Temperature influences quality of most fruits and vegetablesfruits and vegetables

• Most plants will not grow below 40°F or Most plants will not grow below 40°F or above 96°Fabove 96°F

TemperatureTemperature

• Cool season cropsCool season crops

• Day temperatures 60 - 75°FDay temperatures 60 - 75°F

• Night temperatures 50 - 60°FNight temperatures 50 - 60°F

• Tolerate some frostTolerate some frost– Spinach Spinach – Radish– Radish – Carrots – Carrots– Cabbage Cabbage – Beets – Beets – Onions – Onions– LettuceLettuce – Peas – Peas

TemperatureTemperature

• Warm season cropsWarm season crops

• Day temperatures 70 - 85°FDay temperatures 70 - 85°F

• Night temperatures 60 - 70°FNight temperatures 60 - 70°F

• Usually do not tolerate frostUsually do not tolerate frost

• Should not be planted until the ground Should not be planted until the ground warmswarms– CornCorn – Tomatoes– Tomatoes– BeansBeans – Vine crops – Vine crops

TemperatureTemperature

• PhotosynthesisPhotosynthesisCOCO22 + H + H22O O CC66HH1212OO66 + O + O22

• RespirationRespirationCC66HH1212OO6 6 + O + O22 COCO22 + H + H22O O

• ThereforeTherefore: : Photosynthesis leads to an increase in growth and Photosynthesis leads to an increase in growth and

storagestorage

Respiration leads to a decrease in storage and reduced Respiration leads to a decrease in storage and reduced growthgrowth

TemperatureTemperature

• Growth and plant yield = P - RGrowth and plant yield = P - R

• During the day, both photosynthesis & During the day, both photosynthesis & respiration take place but at night, only respiration take place but at night, only respiration takes placerespiration takes place

• Best to keep temperatures warm during Best to keep temperatures warm during the day and cool at night!the day and cool at night!

• Respiration increases more than Respiration increases more than photosynthesis at high temperaturesphotosynthesis at high temperatures

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40°F40°F 96 °F96 °FToo cold Too cold for growthfor growth

Sugars burned Sugars burned up as fast as up as fast as made. No net made. No net growthgrowth

photosynthesisphotosynthesis

respirationrespiration

TemperatureTemperature

• Heat unitsHeat units

• Growing Degree Unit = Growing Degree Unit =

Mean temperature - Base temperatureMean temperature - Base temperature

• Base = either 40 or 50 depending on cropBase = either 40 or 50 depending on crop

Heat units (example)Heat units (example)High Low Mean Base GDU

60 50 55 40 15

90 70 80 40 40

85 55 70 40 30

40 34 37 40 0*

888555

* if mean is less than base, enter “0”* if mean is less than base, enter “0”

TemperatureTemperature

• Uses of Heat Units:Uses of Heat Units:– Predict time to harvestPredict time to harvest

• PeasPeas

• ‘‘Accord’ takes 1150 GDUAccord’ takes 1150 GDU

• ‘‘Nugget’ takes 1570 GDUNugget’ takes 1570 GDU

• ‘‘Alderman’ takes 1700 GDUAlderman’ takes 1700 GDU

• CornCorn

• ‘‘Aztec’ takes 1330 GDUAztec’ takes 1330 GDU

• ‘‘Butter and Sugar’ takes 1570 GDUButter and Sugar’ takes 1570 GDU

Temperature

• Uses of Heat Units: Uses of Heat Units: (continued)(continued)– Predict flowering datePredict flowering date– Predict certain pest problemsPredict certain pest problems– Determine if a crop will grow in a certain Determine if a crop will grow in a certain

area!area!

PhenologyPhenology

• PhenologyPhenology– Relating the development of one plant to Relating the development of one plant to

some aspect of anothersome aspect of another– Greek for “the science of appearances”Greek for “the science of appearances”

PhenologyPhenologyLilacLilac

When in flower, time to plant tomatoes

PhenologyPhenologyForsythiaForsythia Rose Rose

When in flower, time to prune your roses!When in flower, time to prune your roses!

Winter temperaturesWinter temperatures

• Winter injury often occurs from:Winter injury often occurs from:

– Intercellular ice formation (between cells)Intercellular ice formation (between cells)

– Intracellular ice formation (within cells)Intracellular ice formation (within cells)

Winter temperaturesWinter temperatures• Factors that influence hardiness:Factors that influence hardiness:

– Kind of plant (ex: apple vs. peach)Kind of plant (ex: apple vs. peach)

– Temperature during autumnTemperature during autumn

– Soil moistureSoil moisture

– LightLight

– NutritionNutrition

Hardiness curve Hardiness curve (degree of hardiness attained)(degree of hardiness attained)

A S O N D J F M A M J JA S O N D J F M A M J J

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LowLow

HighHigh

MonthsMonths

Winter temperaturesWinter temperatures

• Minimum temperature and when it occursMinimum temperature and when it occurs

• Rate of freezingRate of freezing

• Length of time frozenLength of time frozen

• Number of times frozenNumber of times frozen

• Amount of snow coverAmount of snow cover

• WindWind

Winter temperaturesWinter temperatures

• Symptoms of winter injurySymptoms of winter injury– Dead flower budsDead flower buds– Dieback of shootsDieback of shoots– Brown needlesBrown needles– Bark splits (common on Norway maple)Bark splits (common on Norway maple)– SunscaldSunscald– Root injury/low vigorRoot injury/low vigor– Frost heavingFrost heaving

Winter damageWinter damage

catfacingcatfacing

Winter damageWinter damage

Bark splitBark split

FungiFungi

Winter injuryWinter injury• Winter injury is often associated with a Winter injury is often associated with a

particular set of conditions:particular set of conditions:– Plants grow too late in the fall (Japanese maple)Plants grow too late in the fall (Japanese maple)

Winter injuryWinter injury– Extreme cold too early in fall or winterExtreme cold too early in fall or winter

– Drying windsDrying winds

– Mid-winter warm period followed by severe Mid-winter warm period followed by severe coldcold

– Lack of snow coverLack of snow cover

Winter damageWinter damage

Snow lineSnow line