Saturday, April 28, 2007

Inconvenient question: Invasive species

Invasive species conversations start out simple, and quickly become complex. It is the nature of the wicked inconvenience that one cannot identify a linear solution. For every solution, which may be used to give definition to the problem, begets a complex decision tree which clearly shows that there are no right or wrong answers, but rather better or worse answers. Today I note a studied request for ideas and information gleaned from the Mid Atlantic Exotic Pest Plant Council listserv.

The first paragraph is the normal anguish which appears at first contact or realization of a problem with our natural areas. Gardeners will recognize this problem as the curse of the weed. A solution of aggressive removal gives rise to the standard definition of invasive species, for the author recognizes the harm, either economic or, in this case, aesthetic-environmental, and given the standard definition, seeks a linear solution.

Dear Plant enthusiasts,
Here in Oakton in Fairfax County my students and
I have spent many many man-hours at our campus
and the adjoining Oak Marr/Tattersall
Park(FCPA)removing invasive aliens and trying to
plant native species that are good for wildlife.
It has been a very difficult battle and as we
prune back and tear up russian olive, asiatic
bittersweet, wineberry, wisteria, japanese
honeysuckle, bush honeysuckle, and japanese
barberry year-after-year, several questions keep
coming to our minds.

Time and practical experience demonstrate another basic assertion of a wicked problem: no absolute end. And further, the seemingly simple problem of removal of all exotic aliens, as only exotic aliens are invasive, a surface definition paradox, for it is a native that would appear to be a major contributor to the system imbalance.

1. In places, such as this one, where the deer
are grazing the greenbrier and other shrubby-type
growth so it is unusable by things like towhees,
thrashers, ovenbirds, kentucky warblers, and wood
thrushes, is it better to allow some of the
invasive shrubs to continue to exist in small
patches for bird-use? I know that many of these
shrubs and vines are spread far and wide in bird
droppings, so they would continue to be a
nuisance-source of invasion, but it seems that
all the other sources that we cannot control
outside our management area will continue to
invade anyways, so why not leave a few patches
for the undergrowth-birds to nest in. By removing
the only shrubs that can grow where deer
populations are high, are we also removing the
only places come bird species can nest and forage
for food? Does anyone know of any studies done
on this?

Next the author trips over a horticultural marketing expediency which in this case is the famous “deer” proof pitch. I like to tell my customers that our deer have a preferred buffet of the following sort: 1st. 500 dollar exotic hostas, followed by most natives, immediately followed by anything purchased, minus a few poisonous plants such as daffodils, followed by pretty much anything else left behind, including car bumpers, in the first serving.

2. Most of the "deer-proof" plants that we have
planted have been decimated by the deer. We have
been cutting Wisteria off the forest trees
because of its death-grip which has killed
several, but the ground for at least an acre is
interlaced with the roots so it has been a losing
battle to try to control it in the undergrowth.
Is it possible to use a cover of invasives such
as shoulder-high wisteria understory, that the
deer don't eat, planting some of the other native
shrubs etc underneath and among them, using them
as a sheild? Similarly could some other native
herbacious plants be planted among the
ground-cover of japanese honeysuckle as a
protection against deer-grazing? HAve any studies
been done on this?

Now the interesting thing about this is that a native deer clan seems to have gotten a taste for a nasty exotic which is encouraging, and connecting the ideas of paragraph 2 with three allows one to try the idea of planting or leaving a few select, perhaps non native hors d’ oeuvres which can serve as a tasty first and, hopefully, only stop for the native species deer. I have heard about an idea of planting crab apples and euonymus as a border hedge to keep the deer satiated outside and the garden or woodland thriving.

3. IN our area the deer are eating the multiflora
rose, seeming to keep it under control. I have
seen some amazing thickets of this plant along
Difficult Run downstream from here that have been
totally eaten by the deer. For this reason we
have not bothered removing the rose, hoping that
the deer will fill up on it instead of eating
some of the other native plants. What do you all
think of this?

Paragraph four may have much to so with the terrifying and awe-inspiring non native earthworm, and the destruction of the natural layers of organic material. There is currently research underway which I think includes the mapping of the invasion and soil alteration which allows the invasive plants to follow. It is the interface between our modern human activities and the last refuges of self sustaining ecosystems which are the battleground, and this is what I think the author is recognizing.

4. We are also finding to our surprise that the
primary battles against invasives are closer to
the road in the pinewoods. The oak-hickory-woods,
perhaps because of its thick leaf litter(?) or
its distance from the road(?) or its shadier
summer interior (?) has far fewer invasives and
requires much less maintenance, especially in
areas away from trails and streams where the
japanese honeysuckle, japanese barberry, and
occasionally russian olive are most likely to
occur. As a result we still have some nice
patches of wind-flower, trout lily, toothwort,
violets, jack-in-the-pulpit, paw-paw and even a
little may-apple (unless the deer find it). Have
you all noticed similar things or are we just

Amazingly, ash seedlings, which if Prince George’s County and the state of Maryland cannot finish cutting down, will grow up to succumb to another invasive species the emerald ash borer. I hope to read the many thoughts and ideas that this letter should engender.

5. It is also fascinating to see that of the tree
saplings that are sprouting naturally in the pine
forest, the ones that seem to avoid the deer
grazing are the ashes.

Thanks for your input
Fred Atwood

Frederick D. Atwood
Flint Hill School, 10409 Academic Dr, Oakton, VA 22124

I would hope that if any of my readers have suggestion, that they would write and help; and let me know what you think.