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Combating Invasives

Invasive plants are those that reproduce rapidly and take over wild habitats, out-competing the plants that Mother Nature provided, stealing light, water and nutrients from less aggressive plants. By definition, they are plants that have come here from other countries. They are often very good-looking plants, but thugs. And they can elbow native plants out, sending them towards extinction.

Most invasives produce large numbers of seeds that are distributed by birds, by the wind, or by water. In most cases, invasives are also difficult to remove or eradicate once established, and have extensive root systems that preclude simply pulling them up.

Back home, in their country of origin, most invasives have predators - insects or diseases - that keep their numbers in check. They may have come here inadvertently, or been brought by well-intentioned but misguided people.

Although there are plenty of invasives, recently I've just been working on eliminating one: bush honeysuckle. It has shown up uninvited around my house, and in the woods nearby. I noticed how prevalent they are because honeysuckle leaves appear earlier than those of most other plants.

For many invasive trees and shrubs, merely cutting down plants is a good start, but not enough. Their root systems are full of stored energy and, one might say, attitude. Cutting them down will stop them from producing seeds this year, but most will re-sprout. So I decided to dig up the honeysuckles, at least near the house. Small ones pull quite easily.

I began with a honeysuckle that was about 8 feet tall, and perhaps 25 years old - I'm not sure. I cut the stems off about two feet from the base. These stubs provided me with handles, and some leverage, once I got to work on the stump.

I began by trying to dig a circle around the bush, pushing my spade into the soil as far as I could, trying to cut roots and to loosen up the stump a little. But it wouldn't even wiggle. Next, I dug a hole near the stump a foot deep and a couple of feet wide. Every time I came across a root, I cut it with a small pruning saw I save just for that purpose. Dirt dulls saws quickly, so I have labeled the saw and don't use it for pruning.

I used a 5-foot steel pry bar to loosen up the stump with the idea of pushing it into the hole I'd dug. I worked on the other side of the stump, digging and cutting, cutting and digging. Shortly, I tipped the stump into the hole, and severed the last of the roots. It felt very good, something like, I suppose, victorious warriors must feel after battle. I'd beaten the stump.

Much to the dismay of some in the nursery business, the New Hampshire legislature has decreed that no one may sell, propagate or transport three very popular landscape plants after January 1, 2007: Norway maple, burning bush (Euonymus alatus) and Japanese barberry. They join bush honeysuckle and 22 other plants that are already prohibited. Vermont has a similar list, including honeysuckles. My website, www.gardening-guy.com has the lists for each state.

The laws do not require you to dig up or cut down your invasive plants, but you might consider getting rid of them voluntarily - even if you live in a town or city. You may assume that since there are no forests nearby, it shouldn't matter if you keep your Norway maple (or other invasive species). But Dr. Douglas Cygan, the Invasive Species Coordinator for the NH Department of Agriculture has this response: "It's not just wind or birds that distribute seeds. Runoff can carry seeds through subsurface drainage systems to an outlet in a natural environment. Seed from your tree can end up in streams, rivers, ponds."

Cygan also noted that some people don't believe that "Crimson King", one of the most commonly sold cultivars of Norway maple, is a problem. It has rich red-purple leaves - but these leaves are never seen in the wild. He said that all Crimson Kings are clones of one plant that had a genetic mutation. But when Norway maples reproduce by seed, they produce green-leaved progeny.

There is good news about bad plants. Get rid of them, and you have room for new plants. Here's what I intend to plant as replacements for my honeysuckles. First I will plant a fothergilla (Fothergilla major). It's hardy to Zone 4, 6-10 feet tall and wide. It has white bottlebrush flowers in spring, lasting 3 weeks, and exceptionally nice fall foliage colors.

Next, I will plant common ninebark (Physocarpus opulifolius) It's hardy to Zone 2, 5-10 feet tall and wide. 'Diablo' has nice reddish purple foliage, as does 'Summer Wine', which stays smaller, about 6 feet. They have nice white or pinkish flowers in mid-summer.

So take the afternoon off, and get to work outside. Tell your boss I said it's okay.

To see a list of invasive plants for Vermont, Maine and New Hampshire, click here Invasives List.

Henry Homeyer is the VT/NH associate editor of People, Places and Plants magazine. His website is www.gardening-guy.com. He may be contacted at gardening.guy@valley.net, or P.O. Box 364, Cornish Flat, NH 03746.