Archive for April, 2010

Invasiveness

Friday, April 30th, 2010

In general, the greatest fear of tree care professionals regarding the planting of exotic species, is that they will become invasive, i.e. they will take over landscapes and replace more desirable species (usually natives) growing in that landscape. Not all exotics are invasive, however, and there are other reasons for not planting them. A good example of this latter point is Norfolk Island pine. It is widely used in the U.S. as a potted, indoor plant because it gets too cold almost everywhere for it to survive outdoors; thus it is a waste of time and money to try and use it here. Others are not useful because they simply do not perform as we would wish.

Invaders, on the other hand, are great at performing well beyond our expectations, and can quickly become pests that are difficult and expensive to control and/or eradicate. Some native species of native species can also be classified as invasive because they are prolific seeders or sprouters, and they can occupy ground where we don’t want them in an urban landscape. Again, they become expensive to deal with when they invade areas where they are not wanted; in effect they become a “weed” that must be removed, much like dandelions in a neatly kept lawn area.

Of course we all know the definition of a weed: it is a plant that is out of place. An analogy would be the difference between soil and dirt: dirt is simply soil out of place.

The tendency of various plants to become invasive is not very often noted on tags attached to trees offered for sale, nor is this tendency spelled out in many publications about species selection. Actually, it would be difficult to do this, especially for urban situations, since these tendencies would vary widely depending on where the species is planted. For example, a tree that might spread easily to an adjacent park (if not controlled), might have a hard time spreading anywhere if it was planted as a ground cover in an island surrounded by asphalt in a large parking lot. Even though the tendency to spread may not be spelled out on a tag or in a publication, the nurseryman or other tree care professionals can probably answer that question for you with only a vague description of where you want to plant the tree. All you have to do is ask.

Invasiveness can be a problem that one shouldn’t have to deal with if you make wise species selections when establishing your home landscape. In general, you can’t get into much trouble if you use native species recommended for your vicinity, and for the purpose(s) for which they are suitable.

The Lure Of Exotics

Friday, April 16th, 2010

There is something alluring about exotic plants that leads many people to desire them in their home landscape, more so than native trees and shrubs. My dictionary defines exotic as : 1. foreign; 2. strangely beautiful, enticing, etc. I tend to think of an exotic plant as something one ” just has to have, because it is soooooooooo________________(beautiful, different, sexy, quick to grow, easy to take care of, etc. – just fill in your own descriptor). I didn’t use the words “lust for,” since we’reĀ  talking about plants and not someo….er…… thing else. I can’t envision lusting for a plant of any kind, but I do know there are many different folks out there, with many different ideas. Soooooooooo, who knows?

In general, I think most people have planted exotic tree species, because they believe they will grow better and produce better results than the more commonly available native and naturalized species. Sometimes this works out OK. A good example is Scot’s pine, which is widely grown in Missouri for Christmas trees, with no apparent harmful effects on native ecosystems; especially since it is a short term crop cultivated and cared for in a farming-type manner. Another example of a good exotic species, for urban use, is Japanese zelkova. This species is touted as a fairly good replacement for American elms which have been wiped out by Dutch elm disease. It is not a perfect replacement, but has many elm-like characteristics, since it is a relative of the American elm, and appears to be relatively resistant to the disease. Zelkova Also has good pollution, wind, and drought tolerance, which speaks well of it in urban settings.

There are many other examples of exotic species filling a void in urban landscapes where natives and naturalized tree species have failed, for one reason or another. However, there are probably just as many, if not more, examples of exotics not performing heroically in either urban or rural situations. Japanese honeysuckle is a good example. This sweet smelling, seemingly innocent invader of forest understories has wreaked havoc by forcing out native understory plants, without any significant replacement of the soil-holding functions or wildlife benefits of natives like fragrant sumac or buck brush. Some folks may lust for that aroma though.

Some commonly seen exotics in Missouri have characteristics that make them poor choices for planting: Siberian elm, mimosa, Russian and autumn olives, callery pears (especially Bradford pear), Austrian pine, Lombardy poplar, and Tree-of-Heaven (Ailanthus). Even though you may be a fan of some characteristic each of these trees possess, you should avoid planting them in Missouri. We have many good natives that will perform just as well, even if they may be less alluring on the outside.

Before falling for the allure of an exotic tree species, check it out first. Make sure it is suited to Missouri conditions, and is recommended as an alternative for a situation where natives or naturalized trees have already failed to perform. Don’t let the “siren’s song” lure you into a whirlpool of sadness later on. Good luck.

Random Thoughts

Saturday, April 3rd, 2010

Some random thoughts on the tree care scene:

There are some good fruit-producing trees that also make good landscape trees, if placed correctly and managed properly. Pretty blossums in the spring, shade in the summer, and something good to eat in the fall; a hard combination to beat.

How you prune and care for a young tree during its first few years will affect its shape, strength, and life span. Quoth the bard, “As the twig is bent, so is the tree inclined.”

Eastern redcedar is not really a cedar at all; it is an upright juniper, which has been unfairly maligned because it tends to be an early invader of abandoned, and poorly treated farm lands. However, it has many fine characteristics that make it a desirable landscape tree in urban settings throughout Missouri. It is an alternate host for cedar apple rust, however, and should not be planted too near apple trees. The rust doesn’t hurt the redcedars, but can do a number on apples, especially in “wet” years.

Trees that grow fast, usually go down hill fast too. Be careful of advertisements promising fast shade and longevity. Remember: Right Tree, Right Place.

One of my favorite trees is northern red oak. I don’t have room for one, but I do have a close cousin, a shumard oak, in my back yard. How about you?

I have a great place for a red oak, or a sugar maple (one of my wife’s favorites), but the spot is occupied by a callery pear (not a Bradford), that doesn’t seem to want to give up the ghost so I can replant with a favorite. The previous owner of my home planted it, and it is doing well; even surviving a pretty good ice storm, so I’m going to leave it for a while just to see how it does. It’s pretty right now, I will admit.

Common tree names have always fascinated me, ever since I studied taxonomy back in college. I noted redcedar above as not really being a cedar. Here are some others:

Douglas fir is not really a fir; it is a false hemlock!

Baldcypress is not a cypress; it has been around a long time and is in a class all by itself.

Scotch pine is most commonly used for Pinus sylvestris, but throughout most of the World it is known as Scot’s pine.

And, finally, one of my favorites; spruce pine (Pinus glabra).

The world of taxonomy is sure exciting, eh?