Extension Communications
3614 Administrative Services Building
Ames, Iowa 50011-3614
(515) 294-9915
2/14/00
Contacts: Jeff Iles, Horticulture Extension, (515)
294-0029, iles@iastate.edu
Elaine Edwards, Extension Communication Systems, (515)
294-5168, eedwards@iastate.edu
Yard and Garden Column for the Week Beginning Feb. 18
Great Expectations
By Jeff Iles
Extension horticulturist
Iowa State University Extension
As wise and informed shoppers, most of us enter into business transactions with well-defined expectations regarding the products and services we purchase. For example, we expect to finish a gallon of milk long before it turns to cottage cheese. A good pair of running shoes should hold up for at least one season. And I fully expect my Barry Manilow Greatest Hits CD to sound just as good in 2040 as it does today.
But what of our conifers? You know -- those stately evergreen trees that provide welcome relief to a colorless February landscape. What is an appropriate life-span for the pine, spruce or fir you planted last September? Ten years? Twenty years? One hundred years? Actually, this is a difficult question to answer. For some people, a conifer becomes a candidate for the compost heap at the first sign of trouble. Others who are more tolerant or less observant will put up with shedding needles and thinning canopies until either the plant dies or keels over in a strong wind. As it turns out, beauty, and maybe more important, function, is in the eye of the landowner.
When selecting conifers for the Iowa landscape, remember that there are no perfect trees. Yes, some have significantly fewer problems than others, yet it seems all conifers have an Achilles heel that may cause them to have an abbreviated life-span or shabby appearance. Part of the problem lies in the fact that we are not situated in what might be considered prime conifer country. Sure, our native soils are good enough, however, in many cases, we're not planting into good native soils. Rather, we're chiseling planting holes out of compacted subsoil left by building contractors that bears no semblance to the original soil. But even on fertile, well-drained soils, conifers in Iowa must contend with strong, desiccating winds, extremes in temperature and humidity, and on occasion, branch splintering ice and snow storms. And to make matters worse, conifers under stress often become inviting targets for insects and diseases. Clearly, the deck is stacked against conifers residing in Iowa.
Should there be a moratorium on planting certain conifers? Well, it all depends. If your expectations are such that 15 to 20 years of relatively trouble-free service is good enough, then you won't be disappointed with the likes of Austrian and Scotch pines. But, don't come whining to me when, at the ripe old age of 20, your Austrian pine looks like it's suffering from an advanced case of mange, or your Scotch pine is doubling as a singles bar for bark beetles and/or nematodes. Honestly, if I was in the market for a conifer, I'd set my sights just a little bit higher and try one of the following trees.
Firs, with their narrow-conical outline and soft, silver-blue needles, seem to be everyone's favorite group of conifers, yet many are poorly adapted to hot, dry summers typical in the Midwest. Fortunately, white fir (Abies concolor) is more heat and drought tolerant than many of its brethren and performs admirably in Iowa, as long as it's not planted on poorly-drained sites. White fir should be located in full sun and with plenty of room to grow. Trees easily can grow 30 to 50 feet tall and 15 to 20 feet wide and in my opinion, look their best when allowed to branch to the ground. Just remember, improper installation (planting too deep), especially on poorly-drained soils or where water from sprinklers or rainfall tends to collect, will terminate the life of your white fir prematurely. Fraser fir (Abies fraseri) also is a very handsome and popular conifer, yet its performance is dependable only in Iowa's northeastern corner.
Many people are familiar with Norway and Colorado spruce, but are you acquainted with Serbian spruce (Picea omorika)? Mature specimens will approach heights of 50 to 60 feet and spread about 20 feet across. Its side branches are relatively short, but curve upwards, imparting a very graceful, slightly formal appearance. Serbian spruce can be used as a single specimen, or in odd-numbered groupings if the site is large enough to accommodate such a planting. It also is quite adaptable to alkaline soils.
Looking for an alternative to Eastern white pine? For starters you might consider Swiss stone pine (Pinus cembra). When young, trees resemble dense green columns, but gradually take on a less formal, more open appearance. Because Swiss stone pine only grow 30 to 40 feet tall and half as wide, they are easier to use in cramped residential yards than white pine. And unlike white pine, the needles of Swiss stone pine persist up to five years, giving the tree a full-bodied appearance.
While I don't recommend it, the branches of limber pine (Pinus flexilis) can actually be tied in knots. Aside from this curiosity, limber pine is a fine tree for Midwestern landscapes. Easy to transplant and very adaptable, limber pine will grow 30 to 50 feet tall and at least half as wide, becoming rather open and picturesque with age.
One more pine worthy of note is Korean pine (Pinus koraiensis). Very adaptable and quite cold hardy, Korean pine sports attractive blue-green to gray-green needles and a somewhat informal, loose-pyramid outline. Although it can grow 30 to 40 feet all and half as wide, it will fit most residential sites far more easily than the gargantuan white pine.
Finally, if you like the idea of conifers with fall needle color, then you might consider the tough and durable European larch (Larix decidua), or the slightly more site-sensitive baldcypress (Taxodium distichum). In fall, the rich green needles of European larch turn amber-yellow, while those of baldcypress turn rusty-orange to brown before falling to the ground. Both of these deciduous conifers can grow quite large (well over 60 feet tall), so give them plenty of room. Neither tree is overly picky about where it grows, however, baldcypress will object if planted on soils with high pH.
So, how high are your expectations? Will you plant Austrian and Scotch pine and enjoy them for the short term? Will you trudge along with the same old trio of Norway spruce, Colorado spruce and white pine? Or, will you expect more from your conifers and boldly lead your neighborhood into the 21st century with exciting and adventuresome conifer choices? I'll be watching.
ml: isugarden
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