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Getting Rid of Invasives
Honeysuckle leaves are oval and opposite each other on the stem
For me, those include bush honeysuckle (Lonicera spp.), barberry (Berberis thunbergii) and common buckthorn (Rhamnus cathartica). I recently organized a work day on a hiking trail in Cornish that focused on honeysuckle and barberry. We tried to pull these shrubs by hand, but also used a device called a weed wrench for bigger specimens.
A weed wrench allows anyone to pull out invasive shrubs
Although weed wrench is used generically, it was in fact a trade name, but the company has gone out of business. Similar tools be found under the name “Pullerbear”, “Uprooter” and perhaps others. I have used Weed Wrenches, but not other brands. These are steel tools with sturdy handles and a gripping mouthpiece that bites onto the stem of a shrub up to 2 or 3 inches in diameter, depending on the model. You pull back, and with great leverage you pull out the culprit, roots and all. Some brands come in different sizes.
Buckthorn often grows with several stems in a tight grouping
Buckthorn is one of those that responds to cutting by sending up many new plants. Instead of one buckthorn or a clump of buckthorn, you get dozens of buckthorn. But you can kill buckthorn by girdling the trunk. Take a small pruning saw and cut through the bark all the way around the trunk. Don’t cut into the hardwood, just cut the bark. Then go 12 inches higher up, and do it again.
This barberry planted at our posts office has red leaves, but most have green ones. All have thorns and red berries in winter
Likewise, when there is a bad infestation of an invasive plant like honeysuckle or barberry on a property, look around for spots where a single small plant is growing. It will be easier to pull than a big one. And within a few years, a small plant will be a big plant producing seeds for birds, wind or water to move to a new location – and to produce a big patch. So put out the glowing ember first, then work on the big fire – or infestation – next.
Weeding
I love weeding. It creates order out of chaos, something I have come to appreciate. An un-weeded flower bed is full of distractions. My brain is constantly instant messaging me: “See that dandelion? You should pull it”. The weeds distract me from the beauty of the flowers and the texture and color of the leaves. I feel better as soon as I get my weeds pulled. That said, I still have weeds. Maybe I need to retire from writing a column!
Weeding also makes my plants thrive. Weeds compete with vegetables and flowers for sunshine, moisture, nitrogen and micro-nutrients. In the early spring when my perennials are just waking up, I am very careful not to yank their little green sprouts, thinking they are weeds. In fact, I often let some of my weeding go until late May or even mid-June when everything is obvious.
Drain spade and burdock roots it dug
Dandelions, weeds that I don’t mind in the lawn, can get a bit rambunctious in the garden beds, and I pull them without compunction. Because they have a deep taproot, they are best pulled when the soil is moist. I use a long narrow shovel, one sold as a “drain spade” to loosen the soil down 12 to 16 inches. This spade is just 6 inches wide but the blade is16 inches long. I push the blade deep into the soil, pull back a little, then push it forward, and then slowly pull out the weed, the slower the better.
Sometimes I see a little dandelion and just grab it and pull – only to have the top break off while the roots remain. Whenever you leave dandelion roots, or even fragments of root, the plant will grow back.
Burdock and thistles also have tap roots, some going down very deep. The older the weed, the deeper the root. I’ve pulled mature burdock plants with roots nearly two feet deep. This is only possible when the soil is moist.
It’s really critical, especially for any weed that produces lots of seeds, that you not let them flower. If you don’t have time to dig them out, at least snip off the flowers. Many weeds have green flowers, and some will produce seeds even after being pulled if they have already formed flowers. I don’t throw noxious weeds, things like goutweed, in the compost pile for fear they will grow and spread – or leave seeds.
My favorite weeding tool is the CobraHead weeder (www.CobraHead.com). This is shaped like a tine on farmer’s cultivator – or a bent steel finger. I like it because it is narrow in profile and curved in a way that allows me to easily get the blade under the roots of a weed. I pull from below with the CobraHead while pulling the tops from above. I drag it through the soil in a bed after weeding and am always surprised by now many fragments of root it brings to the surface. I can use it with one hand or two. I use it for loosening the soil while planting, too. It is neither right- or left-handed, it is lightweight, and the handle is made from re-cycled plastic.
The CobraHead is great for teasing out long roots, too. I once pulled out a root 39 inches long in one piece, just gently loosening with the tool while tugging on the weed. That root was from a Queen of the Prairie (Filipendula rubra), a lovely pink-flowered perennial thug. It’s great for teasing out roots of invasive grasses.
Flame weeder
Another great weeding tool is a favorite of my comic hero, Calvin, of Calvin and Hobbes. I refer to my flame thrower. It is technically a flame weeder, but Calvin and I refer to it as a flame thrower. It’s a metal wand on a 10-foot rubber hose attached to a propane tank normally used for gas grills. Light it, and it sends a flame out of the nozzle that will turn any weed crispy in an instant.
I often use my flame weeder on freshly turned soil. I let weed seeds germinate for a week or more, then burn them off before I plant. I try not to disturb the flamed soil when planting, as seeds that have been buried deeply will not germinate, but those on the surface, or near the surface will. Many weeds have what I call a photo-trigger. No light? They won’t germinate. Or I will flame, then plant seeds, then flame again before my carrots are up. Available from Johnny’s Selected Seeds or Fedco Seeds.
Garlic mustard leaves
One of the worst weeds in the world is garlic mustard. Not only will it outcompete other plants in the understory, it can grow in full sun to full shade, and can produce many tens of thousands of seeds per square yard. Garlic mustard is also allelopathic, meaning that it produces chemicals that inhibit the growth of other plants and mycorrhizal fungi needed for healthy tree growth and tree seedling survival.
A friend last year hired a guy to pull all the garlic mustard under her trees and shrubs. It pulls easily, and he quickly filled wheelbarrows full of mature plants. But this year there were thousands of tiny garlic mustard seedlings popping up all over, even in the bark mulch he had put down. I lent him my flame weeder, and in no time he had burned off the small plants.
Many weeds can be deterred by a good thick layer of mulch. Seeds don’t germinate, or seedlings can’t push through the mulch, particularly if you lay down 4-6 sheets newspaper before mulching. Other, aggressive weeds will. Mature Japanese knotweed roots have been said to push through an asphalt driveway! Still, most garden weeds are really just enthusiastic plants that want to be your friends! My practice is to pull weeds every day, and that way I hope to finally beat them. Hah!
Henry is a garden writer, public speaker and garden consultant. He lives in Cornish Flat, NH. You may reach him at henry.homeyer@comcast.net.
Garlic Mustard
As a garden writer I get a lot of email from people warning me about pending catastrophes: blights, bugs, invasive plants. Some are accurate, some are not. In 2012 we were told that a disease kills Impatiens (a lovely annual flower for shade) would make growing it impossible – ever again. But last year it did fine for many gardeners. Late blight on tomatoes is predicted every year, but my tomatoes have only been affected once. But I recently learned some disturbing news about an invasive weed, garlic mustard (Alliaria petiolata), that we should all pay attention to.
Invasive plants generally out-compete our native plants because they grow anywhere, often putting out leaves earlier in the spring than our natives, and holding them longer in the fall. Some, like the Norway maple, have roots that suck up water and nutrients far from the mother plant. Others, like barberry or honeysuckle, shade out natives in the understory of the forest. But garlic mustard, a seemingly innocuous little weed with a root system that is not hard to pull, goes one step beyond the others: it produces a toxin that kills necessary root-coating fungi on our maples, oaks and beeches. Where it grows, some of our favorite trees are in danger.
You may know that mycorrhizal fungi are beneficial fungi that coat the fine root hairs of many trees and perennial plants. They get sugars from the green plants and, as payback, share minerals that the green plants need but can’t extract from the minerals in their natural state. The mycorrhizal fungi produce acids that dissolve minerals in the soil and make them into a form that is readily taken up by the green plants. It’s a perfect symbiotic relationship: you scratch my back, I’ll scratch yours.
Here’s the bad news: Garlic mustard kills mycorrhizal fungi by producing chemicals and releasing them into the soil. Maples, oaks and white ash are all trees that depend on mycorrhizal fungi to succeed. Not only that, garlic mustard inhibits the germination of seeds of many species of native plants, including many spring wildflowers. And it has no natural predators here in the United States where it has invaded from Europe. In Europe it has at least 69 insect predators. Garlic mustard produces chemicals that make it uninteresting as food to herbivores like deer, as well as to insect predators.
Garlic mustard flowers
So what can we do? First, understand its life cycle and learn to identify it. Garlic mustard is a biennial, meaning that it has a 2-year life cycle. In the first year it produces a low rosette of rounded leaves. The second year it sends up 18- to 36-inch flower spikes with pointy, heart-shaped leaves with jagged edges. The small white flowers have 4 petals and bloom in clusters about an inch or more in diameter. One plant can produce about 4,000 seeds. And although about 70% of the seeds will germinate the next year, some will remain viable in the soil for up to 10 years. A Web site full of good information is http://www.invasivespeciesinfo.gov/plants/garlicmustard.shtml.
Garlic mustard leaves when crushed smell a bit like garlic. Not as strong, but it has a distinct odor. The Europeans that brought it here in the 1860’s often grew it as an herb or a garlic substitute, and I have tasted pesto made from the leaves. But since it produces cyanide at a level much higher than other plants, I choose not to consume it. I figure that if the deer won’t eat it, I won’t either.
Here’s the good news: pulling up garlic mustard is easy. It has a white tap root that comes right out if you give it a tug. It is not like many pest weeds – it doesn’t spread by roots that easily break off and start new plants. Goutweed, Japanese knotweed and witch grass all spread by root, but garlic mustard does not. After pulling it, place garlic mustard in the household trash, not the compost pile. Or if you must, seal it in black plastic bags and let it rot in the sun until full decomposed.
First year garlic mustard leaves
How can you help to prevent its spread? Pull it if you see it. Watch for first year plants – it sometimes arrives in hay used for erosion control – it will grow in full sun or full shade. A good close mowing of plants will help, though one report I read said that garlic mustard cut at 10 cm (roughly 4 inches) would survive 29% of the time.
Garlic mustard is blooming right now! So go look for it. Organize a neighborhood group for a “pulling party”. It behooves us all to look out for it, and to do our best to reduce its numbers and prevent its spread.
Henry Homeyer can be reached at henry.homeyer@comcast.net. He is the author of 4 gardening books and a children’s chapter book about a boy and a cougar. His website is www.Gardening-guy.com.
Dealing with Invasives
Purple loosestrife closeup
I’m sure you know purple loosestrife, even if you don’t know its name. It’s a big, tall clumping plant bearing bright pinkish-purple flowers and it’s appearing now in your neighborhood, especially in wet areas. What you may not know is that it’s an aggressive foreign invader that can out-compete many of our native species. It has been around for a couple of centuries – it came over, allegedly, in soil used as ballast in sailing vessels in the late 1700’s.
But if it grows well and it’s pretty, what’s the problem, you may wonder? A number of things. It’s a big plant that can dominate the landscape and shade out smaller, less vigorous native plants. A mature loosestrife can produce up to a million seeds, seeds that can be carried by streams to new locations. Wildlife can be negatively impacted. Many insects and birds depend on native plants for food and nesting materials- native plants that evolved with them. Invasives like purple loosestrife often do not meet their needs.
According to Barbara McIlroy of Etna, NH, who has been active in the movement to control invasive species, the number of bird and butterfly species present on properties that grow native species is much, much higher. “I’m converted,” she told me. “Grow natives. Period. The positive effect on the wildlife is dramatic.”
Unfortunately, it’s almost impossible to rid your property of purple loosestrife. These plants have amazingly tenacious roots. Before I knew better I tried digging out some large plants from a swampy area on my property. Yes, I got the plants out – but some of the roots broke off and re-sprouted. And by clearing out a space, I also opened up a new site for seeds to grow. If you have had purple loosestrife in the past, there are seeds waiting for a chance to germinate – like little time bombs.
Loosestrife
But there is good news: two species of beetle (Galerucella calmariensis and G. pusilla) have been approved for and found effective in controlling purple loosestrife. These beetles cannot eliminate the loosestrife, but can reduce the numbers dramatically. Loosestrife is not a problem in Europe the way it is here, in part because it has natural enemies – the beetles. By introducing the beetles, an effort has been made to help Mother Nature keep loosestrife under control. Once established, they eat enough of the leaves and stems that the plants do not bloom. And theses beetles have been well tested: they will not eat your garden plants or valuable crops.
In 2001 Saint-Gaudens National Historic Site in Cornish, NH released two species of beetles to see if they could control the purple loosestrife that was taking over the wetlands at Blow-Me-Down pond. I met recently with Steve Walasewcz, who monitored the effort from 2001 to 2008. He explained that the beetles did not have an immediate effect. In fact, from 5.75 stems per square meter in 2001, the numbers increased to 10.5 by 2003. But then they declined each year until reaching only 1.05 in 2008 – a tenth the number of stems.
I went to the area where the beetles were released in 2001 and although there were a few blooming stems of purple loosestrife, there were very few. According to a report done for Saint-Gaudens NHS, it is believed that even low numbers of beetles prevent flowering; at higher numbers, “the beetles can strip the plants of its photosynthetic layer, resulting in high mortality in the winter due to a depleted starch reserve.”
Unfortunately, the beetles are not readily available for purchase. But for several years I have been experimenting with my own way of controlling the problem near my brook. Each year in early July I take pruners and cut back the plants to the ground. I identify them by their square stems that have a reddish color near the ground, and of course their leaves. Then a month later, I do it again – in essence, acting like a beetle. By cutting back the plants, few are able to bloom, greatly reducing the number of seeds spilling into my environment.
As a second step, I planted some big, tall native plants that I hoped would compete with the purple loosestrife: Joe Pye weed (Eupatorium purpureum) and Canadian burnet (Sanguisorba canadensis). I also added marsh marigold (Caltha palustris), which though not tall, is tough. These natives have given purple loosestrife a run for its money. Instead of filling 3 wheelbarrows with cut loosestrife in early July, I was able to get it all in one.
Purple loosestrife is just one of many invasive plants. If you see a new, vigorous plant show up on your property, try to learn its name and find out if it’s a problem elsewhere. Meanwhile, there is good news: scientists are working on biological controls for both Japanese knotweed (commonly called bamboo) and garlic mustard. In England, certain beetles are now well established to reduce the vigor of Japanese knotweed.
Henry Homeyer is the author of 4 gardening books and a new children’s fantasy-adventure about a boy and a cougar. His web site is www.Gardening-guy.com.