volume 3 | number 2 spring 2008

climate changesoil as a habitat

species profile

4

spring 2008 great lakes christmas tree journal

Recently we started a new series of articles for the Great Lakes Christmas Tree

Journal profiling conifer species used as Christmas trees in the Great Lakes region.

Some of the conifers we’ll discuss in the series are well known and widely used as

Christmas trees. Others are perhaps less familiar but possess attributes that make

them interesting nevertheless. The goal of the species profiles is to provide growers

with background information on interesting conifers including the ecological and cultural

characteristics as well and some trivial or other interesting tidbits. This issue’s featured

conifer is Korean fir Abies koreana.

Christmas Tree Species Profile:Korean fir Abies koreanaBert Cregg, Ph.D. Michigan State University, Department of Horticulture and Department of Forestry

Abies koreana ‘Aurea’ is a popular form ofKorean fir in the landscape nursery trade.

Botanical characteristics: In itsnative environment, Korean fir is a smallto medium tree, growing up to 50–70'. Asindicated by its common and scientificnames, Korean fir is native to the Koreanpeninsula. The native range is relativelysmall and the species occurs only on thesouthern end of the Korean peninsulaand on Jeju island, just south of theKorean mainland. Korean fir occurs incool moist areas on mountainsides atelevations between 3,000' and 6,000'.Taxonomically, Abies koreana is classi-fied within the genus Abies in the sectionBalsamea, along with Abies fraseri, A.balsamea, A. lasiocarpa, and A. veitchii.Like many other plants from that regionof the world, Korean fir is sufficientlycold hardy (USDA Hardiness zone 4) tothrive in the Upper Midwest, includingmost of lower Michigan. Korean fir tendsto break bud later than other firs makingit less susceptible to late frost injury.

Seventy five years ago in theCultivated Conifers of North America,Liberty Hyde Bailey, in typical under-statement, described Korean fir as “Hardyand attractive.” Both adjectives are appro-priate and go a long ways in explaining

continued interest in the species. Firstand foremost, A. koreana is one of themost forgiving firs in terms of siterequirements. Korean fir will grow wellon a range of sites and is less restrictivein its preferred sites than Fraser fir.Korean fir needles are often described as

dark green but often range toward brightgreen. Needles are relatively short anddistributed along the stem in a bottle-brush arrangement, giving the tree acharacteristic texture.

Growers chime in: Anyone who hasspent more than five minutes with Frankand Cathy Genovese of Candy CaneChristmas Tree farm in Oxford, Michigan

recognizes their enthusiasm for Koreanfir. “We started with 25 seedlings from theMSU exotic fir trial that we bought at aresearch auction”, Cathy remembers.“The seedlings had great, fibrous rootsand grew into full, beautiful trees. Wegrew the first trees on to be 9–10' and we

got great feedback from our customers.We asked some of them to keep the treesdisplayed until late January and they hadgreat needle retention.” The Genovese’scontinue to grow Korean fir and estimateit makes up about 20% of their chooseand cut business. Dan Wahmhoff ofWahmhoff farms in Gobles, Michigan isalso a Korean fir fan. “There are lots of

5

This slow growing form of A. koreana makes an attractive foun-dation plant.

A. koreana is one of the most forgiving firs in terms of

site requirements. Korean fir will grow well on a range of

sites and is less restrictive in its preferred sites than

Fraser fir. Korean fir needles are often described as dark

green but often range toward bright green.

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interesting exotic firs out there,”Wahmhoff notes, “but Korean is aboutthe only one that grows fast enough tomake any economic sense. We’ve grown9–10 footers on about the same produc-tion cycle as our Frasers.”

In the interest of being “Fair andBalanced”, it should be noted thatKorean fir can present challenges thatmay dampen some grower’s enthusiasmfor the species. The most obvious issuewith Korean fir is cones. Most peoplefamiliar with Christmas tree productionin Michigan recognize the problem ofprecocious cone production in Fraser fir,however coning in Korean fir occurseven earlier in the tree’s developmentand more frequently than in Fraser fir. Infact, Korean fir’s propensity for profusecone production has caught the eye ofnursery growers over the years and sever-

species profile

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spring 2008 great lakes christmas tree journal

Abies koreana x lasiocarpa. This hybridcombines the adaptability of Korean firwith the form and color of sub-alpine fir.

al ornamental cultivars of Korean firhave been selected for their distinctivecones (see below). Needle color canalso be a potential issue for Korean fir.As noted earlier, Korean fir is sometimesdescribed as dark green in the literaturebut, compared to many firs, bright greenis probably a better description. As soilnutrients become limiting, Korean fir canquickly slip from bright green to achlorotic yellow-green. Korean fir alsohas a bit of a reputation for producingsquirrelly leaders once pruned. LouWaldock of Waldock farms in Howell,Michigan believes Korean tops can betamed, however. “Sometimes the termi-nal leader can get a little curly,” Waldocknotes,“but we’ve had good success intraining new leaders from laterals.”

Hybrids on the horizon: Many firspecies hybridize readily and Korean fir

is an obvious choice for hybridizationsince it cones readily and has manydesirable adaptive and ornamentaltraits. Several Korean fir hybrids areavailable from seedling nurseriesincluding A. koreana x fraseri,A. kore-ana x veitchii, and A. koreana x lasio-carpa. The goals of crossing speciesare usually to combine desirable traits,produce a plant that is intermediatebetween two species, or to produce‘hybrid vigor’— a cross that is superiorto either parent alone. A hybrid of A.koreana and A. lasiocarpa (see photo)appears to combine desirable traitsfrom both species, combining theadaptability of Korean with the bluishneedles of sub-alpine fir. It is importantto note that species hybrids can oftenproduce surprises. For example, in theMSU exotic fir trials, Korean and Vietch

fir were consistently among the lastspecies to break bud each spring—adesirable trait since it minimizes risk oflate frost damage. Nevertheless, treesfrom a cross between Korean and Vetchfir broke bud two to three weeks earlierthan trees from either parent speciesand were damaged by a late freeze in2004. There are a number of possiblecauses for this phenomenon; the seedsources used to make the cross couldhave been different than the seedsources of the parent species tested orthe cross produced a hybrid vigor (ear-lier budbreak than the parents) whichin this case resulted in a negative trait.The take home message is that we can-not assume hybrids will be superior oreven intermediate to the parentspecies. Each hybrid cross needs to beevaluated on its own merits.

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species profile

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spring 2008 great lakes christmas tree journal

Landscape cultivars: Although thenumber of Christmas tree growers inMichigan dabbling in Korean fir isincreasing, the species is probably morewidely known as a landscape ornamen-tal. The American Conifer Society (ACS)recognizes roughly 40 cultivars of Koreanfir. Some cultivars are obscure, but oth-ers are fairly well known and maybeworth considering for growers that areexpanding into landscape nursery pro-duction.

The list below provides a cross-sectionof the Korean cultivars that are in thenursery trade.

• ‘Silberlocke’ Silberlocke is one of aseries of Korean fir cultivars that fea-ture recurved, or upturned, needles.The recurved needles display the sil-very bands of stomata on the under-side of the needles. The result is astriking silver appearance that givesthe cultivar its name since Silber isGerman for silver.

• ‘Blue cones’ As the name implies,the Korean fir cultivar was selectedfor its prolific blue cones.

• ‘Compact dwarf’ This cultivar ofKorean fir is characterized by its slowgrowth rate. The American ConiferSociety denotes dwarf conifers asthose that growth between 1" to 6"per year and typically reach about 1' to 6' in height by age 10. As withmany ornamental conifers, ‘Compactdwarf’ lacks apical dominance andtherefore appears more as a shrubthan a tree.

• ‘Aurea’ This is a yellow form ofKorean fir. Christmas tree growersaccustomed to striving for dark greencolor, might have to be physicallyrestrained to keep from adding morefertilizer to this one.

Abies koreana ‘Silberlocke’.The recurved needles onthis cultivar make it a silvery showstopper.