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The Firs by Dr The Firs by Dr. Bert Cregg s a native of the Pacific limiting factor. We can adjust soil pH MSU Project GREEEN, we have Northwest, I have always had by applying sulfur or fertilizing with transplanted over 200 of the trees to Aa soft spot in my heart for firs. ammonium sulfate to make a site MSU Horticulture Research Stations From high school summers shearing more suitable for firs, whereas soil across the state and are expanding the deep green grand firs (Abies grandis) drainage is difficult to change across evaluation to include traits that are on Christmas tree plantations to a landscape. Nevertheless, there are critical in landscapes such as response seeing the spire-like crowns of several reasons to expect the use of to soil pH and drought. subalpine fir Abies( lasiocarpa) on firs to increase in the future: day trips to Mt. Rainier, firs were an 3. Introduction of Hybrids ever-present symbol of my Northwest 1. Blue Spruce Burnout One of the interesting features of upbringing. The true firs (genus Since I’ve started this column firs is that many species hybridize Abies) include a remarkable variety people have asked me, “Why do readily. It may be possible through of trees that are important to the you hate blue spruce so much?” hybridization to combine desirable nursery, landscape, and Christmas For the record, I don’t hate blue ornamental traits from one species tree industries of Michigan. spruce (or Norway spruce or Scots (say, needle color or form) with The genus includes over 40 pine or Austrian pine or white pine). stress adaptations from another species distributed throughout the It’s like the old saying, “There are species such as drought tolerance. temperature regions of the Northern no bad dogs, just bad owners”. It’s While we usually expect hybrids to Hemisphere. Firs are single-needled not the fault of blue spruce that it’s be intermediate between their parent members of the pinaceae family and been over-planted. Blue spruce is species, certain crosses may result are distinguished by the fact that easy to grow both in the nursery and in “hybrid vigor”, a type of synergy their cones are borne upright and the landscape; it tolerates poor site in which the progeny are superior disintegrate rather than drop off the conditions and even road salt. But, to either parent. Early results from tree intact. Firs are very attractive as we’re learning again with Emerald our work with the exotic firs from as ornamentals and Christmas Ash Borer, over-planting a single Kellogg Forest suggest that hybrids trees because of their upright and species or even a handful of species of Korean fir such as Korean x Veich symmetrical growth habit. The is a recipe for disaster. Diversity is and Korean x Balsam are well adapted popularity of firs, particularly Fraser strength. for Michigan’s climate. At the 2003 fir (Abies fraseri), as Christmas trees Exotic conifer conference in Clinton, has grown steadily over the recent 2. Introduction of New Species Iowa, hybrid firs were one of the past. While Scots pine was once the Efforts are underway here at MSU hottest topics and many conifer mainstay of the Michigan Christmas and elsewhere in the United States breeders are experimenting with new tree industry, more and more growers to evaluate exotic species of firs that crosses. So look for more hybrid firs are switching production to Fraser may be adapted for use as Christmas to become available in the future. fir. The use of firs for landscaping, trees and ornamentals. About ten however, continues to lag behind years ago Dr. Mel Koelling, MSU 4. Introduction of Inter-specific “tried and true” conifers such as Forestry Department, and MSU Grafts pines and spruces. The biggest reason Statewide Christmas tree Extension Another way to combine traits firs trail other landscape conifers Agent Jill O’Donnell began a from one species with another is by is that many fir species are fairly program to examine exotic firs for grafting a scion (top) of one species exacting in their site requirements. Michigan. To date, they have planted onto the rootstock of another. This As a general rule, firs prefer acidic soil over 40 species and hybrids of firs is a really exciting development conditions, usually the lower the pH, in a demonstration planting at the in efforts to promote and expand the better. In native stands, firs grow Kellogg Experimental Forest near the use of firs. Scientists at North on soils with pHs in the 3-4 range. Augusta, Michigan. The principle Carolina State University are While most people think of pH as goal of the program was to evaluate experimenting with inter-specific a limiting factor in planting firs, in the new fir species for Christmas grafts to overcome problems reality, soil drainage is often a bigger trees. However, with support from associated with phytophthora root 24 The Michigan Landscape™ Bert Cregg Chub Notes John Fertig Justin “Chub” Harper is widely known as one of the leading experts on garden conifers in the United States. The Harper Collection of Dwarf and Rare Conifers at MSU’s Hidden Lake Gardens is nationally recognized. Each Conifer Corner includes Chub’s notes on his favorite (and not so favorite) conifers. rot in Fraser fi r by grafting Fraser fi r (which is highly susceptible to phytophthora) onto species such as Momi fi r that are resistant to root rot. At the 2003 International Christmas Research and Extension conference, the fi eld tour visited a Abies concolor ‘Candicans’ test planting of grafted and ungrafted seedlings of Fraser fi r. Mortality of ‘Gables Weeping’ - An irregular ungrafted seedlings was nearly 100 mounding or weeping form with percent whereas seedlings that were blue-green needles. Zone 3 grafted onto resistant rootstocks had Korean fi r (Abies koreana) Abies koreana ‘Silberlocke’ virtually no mortality. Inter-specifi c Korean fi r is well adapted to grafting also offers the potential to landscapes in Michigan. There are graft onto rootstocks with tolerance Subalpine fi r is another example several excellent specimens at the to adverse soil conditions such as of a high elevation western species Harper Collection at Hidden Lake poor drainage or high soil pH. that does well in our Midwest Gardens and the species and hybrids climate. Our research has shown have done well at the demonstration Noteworthy Landscaping Firs that it is relatively tolerant of soil planting at Kellogg Forest. Several pH compared to other fi rs. Moisture There are a number of fi rs that outstanding cultivars are available in make excellent landscape trees and availability and soil drainage are the trade. Like Fraser fi r, Korean fi r is probably the principle limiting factors this list provides just a sampling. a precocious cone producer. As a general rule, true fi rs are more for this interesting species. demanding in their site requirements ‘Aurea’ - A golden-yellow form then most other conifers. Firs don’t of Korean fi r that is a broad globe like wet feet so avoid sites with poor when young and later develops a Bert Cregg drainage. If your soil pH is above 6.5 leader and grows in a broad upright you may need to add elemental sulfur form. The short needles are bright or fertilize to reduce the soil pH. yellow to golden in color becoming dull by winter. Chub notes: “This is Concolor fi r (Abies concolor) a real show-stopper, especially when Concolor fi r is native to it cones.” Zone 4 mountainous areas of the West. It’s one of the most popular fi rs for ‘Blue Cones’ - As the name implies, landscaping because it will tolerate this cultivar is noteworthy for its higher pH levels than most other fi rs. dramatic blue cones in the spring. Abies lasiocarpa ‘Green Globe’ Chub Harper notes: “Concolor fi r is Zone 5 just about everyone’s favorite because ‘Silberlocke’ - The needles on this ‘Green Globe’ - A dwarf, globose it holds up to heat and cold.” cultivar are recurved (turned upward) form with green needles, Chub notes: revealing the silver underside. The ‘Candicans’ - Upright grower with “This is a reliable plant I rate among result is a striking silver appearance. long silver-blue needles. Zone 4 the top fi ve for dwarf conifers.” Zone Chub notes: “A dramatic and 5 ‘Swifts Silver’ - A superior selection, outstanding tree, this is one everyone exceptional silvery colored needles, lusts after. The only downside is the Corkbark fi r (Abies lasiocarpa var. uniform growth, well suited for silver characteristic of the needles arizonica) ornamental uses and Christmas tree tend to fade with age.” Zone 4 Corkbark fi r is the only recognized production natural geographic variety of A. Subalpine fi r (Abies lasiocarpa) lasiocarpa. The common name derives May/June 2004 25 Bert Cregg Bert Cregg Douglas-fi r: When A Fir Is Not A Fir Douglas-fi r is a classic case of how common names can often lead to Abies nordmanniana confusion. Douglas-fi r is member of a Abkhazia. The species has dark green separate genus, Psuedotsuga, which lustrous needles and is a fast grower. actually translates to “false hemlock”. There are several specimens over To help distinguish it from other fi rs 80 feet tall at the State Hospital at the common name is hyphenated as Traverse City, Michigan. Zone 5 Douglas-fi r. Other common names Douglas-fi r (Psuedotsuga menziesii) such as Oregon pine only add to the Abies lasiocarpa var. arizonica Interior forms of Douglas-fi r are species’ identity crisis. well adapted to Michigan and can While at fi rst glance Douglas-fi r from its peculiar, whitish, corky bark.
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