Y ES, THEY CAN MAKE YOU FEEL VIOLENT, author Teri Dunn Chace admits about weeds in “How to Eradicate Invasive Plants.” In fact, if authors named their own books, this new one might have been called, “The War of the Weeds.” But in that “two wrongs don’t make a right” way of thinking, Teri reminds us that getting out the big guns isn’t where to begin. Understanding who you’re up against, and being strategic, is. We had a lively conversation on the latest radio show and podcast—and I’ve bought two copies of her book to share. Most important: Teri shared tactics for dealing with some of the toughest opponents, from Japanese knotweed to goutweed and more—all on the jump page.
What I like most about “How to Eradicate Invasive Plants” (Amazon affiliate link) is that it contains no magic silver bullets, meaning: It’s honest about the fact that tackling weeds, and even more so a true invasive plant, is no simple matter. One doesn’t wave a wand and solve an infestation from the comfort of a lawn chair, sorry to say. For each of the 200 plants covered, you get a little background on where it hails from, and how it grows and reproduces. And then you simply get told how, and when, to get down to work. Again: refreshingly honest.
prefer the podcast?
WEEDS were the topic of the latest edition of my weekly public-radio program with guest Teri Dunn Chace. Listen anywhere, anytime: Locally, in my Hudson Valley (NY)-Berkshires (MA)-Litchfield Hills (CT) region, “A Way to Garden” airs on Robin Hood Radio’s three stations on Monday at 8:30 AM Eastern, with a rerun at 8:30 Saturdays. It is available free on iTunes, the Stitcher app, or streaming from RobinHoodRadio.com or via its RSS feed. The June 24, 2013 show can be streamed here now. Robin Hood is the smallest NPR station in the nation; our garden show marked the start of its fourth year in March, and is syndicated via PRX.
getting started: teri’s common-sense approach
- Start with weed I.D., and some research. First, you must know what “weed” you are tackling, and how it grows and reproduces. Teri advises that we start with low-impact tactics, which might seem obvious, but really can give us an edge in the fight if we keep them in mind. Things like:
- Intervene early. (“Yeah, right; of course,” you may be saying—but tell the truth: Do you always do so, right when tiny seedlings or sprouts emerge?)
- Time your attack well. (This is where knowing your weed’s biology comes in, because some plants are most vulnerable in spring, and others best fought in fall.)
- Concentrate your efforts. (Zero in on a particular infestation, but don’t treat any unneeded spots beyond the real problem, if you are spraying.)
- Persist. (Again, this seems obvious—but remember these things are called weeds because they are tenacious, so you need to be more so, and that doesn’t mean a round or two. “Give it time,” says Teri.)
- Do no harm. Though chemical controls are included in some of the 200 entries in her book, they should never be the first, knee-jerk resort. “Your yard and surroundings should not suffer harm in the process” of fighting weeds, she writes. Instead, start by capitalizing on insights she shares, such as that gooseneck loosestrife (Lysimachia ciliata) can’t survive in dry soil, which gives you the hint to dry out the area (with plastic sheeting) to beat it.
the worst of foes: knotweed, goutweed, more
I SELECTED A FEW of the worst offenders I hear from readers about, and got Teri’s take on them. Note: What’s below is the less-toxic portion of the book’s recommendation for each plant, since I don’t use chemicals. Sometimes you may wish to, and when the book does recommend them, it’s always in the most targeted, properly timed manner—and again, never as the first line of defense.
Japanese knotweed: This one’s not kidding, admits Teri about Fallopia japonica (also listed as Polygonum cuspidatum): “It is very difficult to eradicate.” In fact, she dropped out of negotiations on a home she wanted to buy when she saw it growing in the yard. “It was a deal-breaker,” she says. But many gardeners are facing this plant, which spreads by seed (dispersed by wind, animals, contaminated fill that’s brought in and so on) as well as by rhizomes that rival the inspiration for its common name, Japanese bamboo (though it is not a bamboo relative at all).
Dig up rhizomes when practical (they can reach massive proportion), or at least cut back topgrowth repeatedly to weaken the root system. “Then smother the area with thick mulch and/or a tarp and leave it in place for at least a year, perhaps longer,” she writes. Yes, you heard that: a year or longer.
Important: If herbicide is used, late summer or fall’s the time, not spring, for it to be effective. Apply it on chopped-back plants, not giant stands. The only good news here: An extract of the roots is used in a treatment for Lyme disease.
Goutweed, or bishop’s weed: Monks in the Middle Ages apparently used this nightmare for treating gout, but Midwest and Northeast gardeners, in particular, probably wish it had never been introduced in the mid-1800’s from Europe and Asia. Both seed and underground runners of Aegopodium podagraria are the issue here.
“In smaller patches, repeatedly yank out or whack back unwanted growth,” Teri says, and remove flowers, too, if practical. “Digging up plants only works if you get all the trailing roots/rhizome bits,” she adds. In larger areas, cut it down with a weed whip or mower, then cover the area with black plastic that must be left in place for months. (That’s the variegated form, above.)
Ground ivy: I’ve got loads of Glechoma hederacea, a.k.a. creeping Charlie or ground ivy, a mint family relative (which tells you something right away about how invasive it can be). Stupidly, until I consulted Teri’s book, I didn’t know that besides its formidable runner system, ground ivy also seeds around—so mowing close at flowering time will help in the battle. So does pulling the runners after a rain (or after watering first), then mowing short to reduce any remaining foliage and potential flowers, too. (That’s it below, with an Oriental bittersweet seedling or two emerging in the midst of it.)
Oriental bittersweet: Celastrus orbiculatus is one of my most prolific woody invaders, seeded in clumps under every tree and shrub here by birds who ate the fruit and expelled the seed. (Above, seedlings sprout in a mass of ground ivy.) Pulling up seedlings when small is the best approach, Teri says, and then something I fail to do: chop back older plants at ground level again and again to exhaust the roots and stop resprouting. Must go on a search for them along the roadside edge, yes I must!
more from teri dunn chace
TERI DUNN CHACE’S 9-point “Weed Prevention for Gardeners” is one of my favorite parts of her new book. Examples: Do you inspect every plant you bring home from a nursery, or a friend, for hitchhiking weeds, then keep an eye on what sprouts near it in the weeks after you place it in the garden? (I’ve inadvertently adopted several of my worst pests by skipping the last bit of that step.) Incoming amendments, such as mulch or topsoil, can be loaded with future problems, too. Another: Sometimes, tilling is a mistake, and only makes for more trouble by unearthing weed seeds. Get the whole excerpted list here. Teri’s website includes information on some of the many other books she has authored, and her other work.
how to win the book
I’VE BOUGHT TWO extra copies of “How to Eradicate Invasive Plants” to share with you. All you have to do to enter is comment in the box below, all the way at the bottom of the page, answering the question:
What’s your most loathed weed?
Don’t worry; if you’re feeling shy you can just say “Count me in” and you’ll be entered in the random drawing. I’ll email winners after entries close at midnight on Monday, July 1. Good luck to all.
(Japanese knotweed stalk-detail photo from Wikipedia.)