Invasives: What are they? What can you do about them?

Posted on Tuesday, September 12, 2023 · Leave a Comment 

I’m lucky. Unlike many houses built in the 1800’s or early 1900’s, mine had no invasive plants when I bought it in 1970, probably because it was built as a Creamery, or butter factory. Decorative plants were not needed. Most older houses are plagued with plants brought from Asia or Europe by well-meaning people who did not know that once imported, those handsome plants might not have any predators that could keep them under control. Most of our native insects will not eat foreign plants.

 

Plants including Japanese knotweed, Asian bittersweet, goutweed, purple loosestrife, yellow pond iris and multiflora roses have thrived in New England – and all are nearly impossible to get rid of, once established. Unfortunately, I now have four of the six mentioned above. But no Japanese knotweed or bittersweet, thankfully (they are two of the worst).

 

Multiflora rose hips are eaten by birds but the plants are invasive and should be removed.

Multiflora roses just showed up on my property last year, probably by birds that dropped seeds. It is easy to see roses growing in your woods or fields, or even in a garden bed and pass it by as “just a rose”. But the roses we love don’t just appear.

 

The multiflora rose was introduced from Asia in the 1860’s as a vigorous ornamental rose and as a source of rootstock for grafted roses. In the 1930’s it was widely introduced as erosion control and alongside highways – a mature planting is so dense it can prevent cars from going over median strips. But the birds liked the rose hips – their seed pods – and it escaped cultivation.

 

So what am I doing to eliminate it on my property? I am digging it out. Most effective for one or two year old plants, I am using a curved, single-tine hand tool called the CobraHead (www.Cobrahead.com) to carefully excavate the roots until I can lift the plant out.

 

Multiflora rose roots radiate out from the central stem

First, I dress appropriately: jeans, long-sleeved shirt, a hat with a brim, and heavy winter leather work gloves. This culprit wants to hurt anyone trying to uproot it. I cut off the branches, just leaving a foot or so to grab onto when pulling it out. Then I loosen the soil and pull weeds around it. The roots radiate outward from the stem like spokes on a bike. I loosen each root and tug gently when they are small enough to remove.

 

I do not burn brush anymore because of global warming, and don’t want any errant seeds to escape, so I cut up the branches and brought them to our town recycling center. I put them into the trash going to the landfill, along with the roots. It took me about an hour to remove and cut up one plant – and I have several. But this plant can grow 10 feet or more in a year, and strangle trees or shrubs.

 

Girdling buckthorn twice with a pruning saw will slowly starve it to death

I’ve read that just cutting back the stems to ground level will stimulate the roots to send up new shoots everywhere, causing a bigger problem. There is no easy answer. Invasive plants are always difficult to remove – usually a scrap of root can generate a new plant – or several.

 

Buckthorn is another invasive that is common along streams and at the edge of fields. Like multiflora rose, cutting it down stimulates the roots to send up new shoots. The best way to eliminate it is to starve the roots: Take a pruning saw and cut through the bark and the green layer of cambium beneath that. Go all the way around the trunk, then repeat six inches above the first cut, and repeat. This will not kill the tree until the third year, but this slow death will not stimulate the roots to grow. Best done in winter or fall after leaf drop.

 

Buckthorn often grows with several stems in a tight grouping

Since buckthorn are often multi-stemmed, it can be difficult to use that method. Do it up high enough that you can get your saw in between the stems. But I’ve done it, and it works.

 

Purple loosestrife is blooming now in swamps and wet places – it is gorgeous, but outcompetes many of our native wetland plants that feed pollinators and other animals. Like many invasives, it produces huge numbers of seeds and these seeds don’t all germinate the next spring – many stay dormant for years. I’ve read that multiflora rose seeds can stay viable up to 20 years – a good reason to clear plants out when young.

 

My approach to purple loosestrife is to dig out new, young plants. I recognize them by their square stem, the leaf shape and the color of the stem which is often reddish. But for big established plants I just use a curved harvest knife to slice off the foliage once or more than once each summer. This prevents seed production, and reduces plant energy.

 

As regular readers of this column k now, I only use organic techniques in the garden. This means no chemicals including herbicides. From what I have read, most herbicides will not kill the invasives mentioned in this article. They will set them back considerably, depending on the age of the plant and the dose of the chemical. But learning to recognize all the invasives is best. And if one appears on your landscape, get rid of it immediately! And remember, persistence is important

 

Henry is the author of 4 gardening books and lectures at garden clubs and libraries. He lives in Cornish, NH. His email is henry.homeyer@comcast.net.

Filed under Article · Tagged with buckthorn, invasive plants, multiflora rose

Invasive Plants

Going for a walk the other day along a public trail I was struck by the number of invasive shrubs I saw. Most trees and shrubs have shed their leaves, but burning bush (Euonymus alatus), Japanese barberry (Berberis thunbergii) and honeysuckle (Lonicera spp.) still have leaves on their branches. Holding leaves and producing food by photosynthesis gives them extra energy to take over the world (or their world, anyway). This is a good time to pull a few of these out because many are very visible right now.

invasive honeysuckle

Why bother, you might ask? Because these invasive plants which come from the China or Japan have no natural enemies here. Left alone, they can take over the landscape, outcompeting our native wildflowers and understory shrubs, although that may take decades. In some places they have created monocultures by elbowing out other plants. Most birds, mammals and insects have evolved while depending on native species for their food and shelter. Do these shrubs provide food? Yes, but it is often not of the same quality as that of our native species.

Cutting down invasive shrubs will not necessarily kill them. Some invasive trees and shrubs react by sending up multiple new shoots from their roots. Instead of one buckthorn, for example, you suddenly have several in a circle around the tree you cut down. That increases the problem instead of solving it.

I have found that buckthorns can be killed without producing the root suckers if I double girdle the tree. By this I mean I cut a ring around the tree with a pruning saw, and then cut another ring a foot higher or lower than the first cut. I cut through the bark and the green cambium layer, but do not cut into the heartwood. If I do this now, the tree will leaf out next spring and the following spring, but slowly die by the third year. Patience is the key. The technique allows you to slowly starve the roots – they can’t get any nutrition from the leaves. Many buckthorns have multiple stems, and you must girdle every one to kill the roots.

Wheeled shrub puller

For small to medium sized invasive trees and shrubs, pulling them up is another option. I recently met with Gerry Hawkes, an inventor and forester in Woodstock, Vermont to try out a tool he developed to pull invasives (and do other tasks such as hauling firewood and moving large stones). It is a sturdy, 2-wheeled device that uses leverage to pull up a tree, roots and all. We pulled an inch-and-a-half buckthorn tree and a full size multi-stemmed honeysuckle with a trunk that was over three inches in diameter at the base.

The tool we used is called a Wheeled Post and Shrub Puller (http://wheeledhandtoolsystems.com). It is made of sturdy 2-inch square steel “pipe” and stands over 6 feet tall leverage when in the vertical pulling position.

Standing on shrub puller for maximum pulling power

We looped a light chain around the base of the tree and then attached it to one of four notches on the puller to allow us to begin with the best mechanical advantage, which is 12:1. I pulled down on the handle using my weight and it lifted the buckthorn partially out of the ground. Then, to get an even higher lift, we reset the chain to a different notch on the front of the tool and I got the root system right out of the ground! Since this tool is on 16 inch wheels, I was able to roll the tree away with little effort.

I have also used a hand tool called a Weed Wrench that pulls small trees and shrubs. Unfortunately, the company that makes these tools has gone out of business. It was made in four sizes with a gripping mouth-part that clamps down on a trunk, and a handle that uses leverage to pry out shrubs. Two other companies are now marketing similar tools, The Uprooter (www.theuprooter.com) and the Pullerbear (www.pullerbear.com). From what I have read, neither would compete with the tool I tried last week for pulling larger shrubs and small trees.

Burning Bush that self-planted

I think that using mechanical advantage to pull invasives makes much more sense than using chemical herbicides. But I don’t have personal experience following up over several years with invasives pulled: will the scraps of roots left in the ground survive and re-sprout? It’s possible that they will. Still, I think that Conservation Commissions and Garden Clubs would be well served by investing in pulling devices to share with interested townspeople and using along public pathways.

There are no plant police. No one can tell you that your invasive shrubs must be pulled up. Nurseries may not sell them, propagate them or transport them. But I am working hard at removing mine. And even if you live in a city, it makes sense to remove invasive plants on your property. Their seeds may wash down storm drains, and end up in a wetland or river – and spread their genetic material.

Getting rid of invasive plants takes time. I recently chatted with a woman who removed all the burning bush on her property 12 years ago. She is still pulling seedlings that germinate from seeds deposited over a decade ago. But, on the positive side, pulling “thugs” gives you more room to plant other nice landscape plants. So go look for invasive plants now, and try to get rid of a few.

Henry Homeyer is a gardening consultant and coach. He speaks to garden clubs and civic organizations about many aspects of gardening. Contact him at henry.homeyer@comcast.net or visit his website, www.Gardening-Guy.com.

Copyright © 2014 Henry Homeyer

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