Even if you have been assiduously pulling your garlic mustard and narrowleaf bittercress you will see that the ones you missed — and there are always some you have missed — have already released their seed. The narrow seed pods — called siliques — propel seeds like little bombs exploding at the lightest touch. I read that single narrowleaf bittercress plant can produce over 5,000 seeds. I think that data point is quite motivating. “Today I pulled what would have been a million weeds next year” you might say after a morning of light weeding.
Some of the larger narrowleaf bittercress plants keep growing and producing seed even after the first seeds have exploded. And some of the garlic mustard has not yet released its seed so they are still worth pulling. You will want to pull the plant from the bottom of the stem, keeping the seed head far from you and surrounding obstacles. Using a contractor’s bag, gently place the pulled plant in headfirst to catch the explosion of seeds. Also keep in mind that some of these plants are top-heavy and will have fallen over, especially with the rain we have had over the past week; try not to step on them. You can keep the bag in the sun for the summer to rot down the contents and dispose as compost the following year.
It all comes down to staying ahead of a plant’s seed production which happens after the plant flowers. After several seasons of this kind of work the sequencing of weed pulling takes on a distinct rhythm. April and May are dedicated primarily to garlic mustard and narrow leaf bittercress eradication then, at least on my property, nipplewort (which is in flower now) the dreaded Japanese stilt grass and then poison hemlock.
The weed currently on Tom Zetterstrom’s mind is mugwort. You might already know Tom; he is a guru for many when it comes to restoring native environments; he has been doing this work on his own 60 acres and for others for decades. A fine art photographer by trade and dedicated to preserving our area’s native elm trees, Tom has seen the woodlands and grasslands in the Northwest Corner change significantly as invasive plants and fungi have wrought havoc to native habitats.
Tom thinks that mugwort, Artemisia vulgaris, may now be more of an environmental threat than Japanese knotweed due to its massive seed proliferation. A single mugwort plant can produce 200,000 seeds (making narrow leaf bittercress an invasive lightweight by comparison.) By seed and by rhizome, mugwort creates dense monocultures and chokes out anything in its way.
It has taken over on roadsides; you will easily identify them by their leaves’ silver undersides. Tom posits that their quick and wide spread is due to the unintended consequence of roadside brush cutting which is done in early spring when the seed heads have not yet grown, then again in late fall, after the seeds are ripe and ready to fall off. The very thing the brush cutting is trying to minimize is making the problem worse.
Even then, brush cutting alone will not eradicate mugwort because it has a rhizomatous root system. You can cut it and it will grow back — again and again. Tom sprays herbicide on swaths of mugwort with glyphosate at a 2% ratio to water with the addition of a surfactant to help it spray well and penetrate the leaves. If you want more info on herbicide best practices, email me at dee@theungardener.com
Over in Sharon, Barbara Zucker Pinchoff has the remnant of a 3700 square foot patch of mugwort. Two years ago, after watching it expand over several years, she sprayed a small area with Roundup as an experiment. It did not work. Researching non-chemical solutions, she had it mowed down and covered the area with black tarps — from BillboardTarps.com, which sells vinyl that has previously been used as billboard creative. She waited (impatiently, as you can imagine with that much of her land covered by several billboards!) for two years. Then an area which had blown off exposed the area. The offending plant looked dead and gone and so the tarps came off. In one area Barbara planted native plugs and also pasture grass; not native, which she regrets, but sufficiently quick to green up and prevent a mugwort comeback. In another part of the plot she seeded with a combination of native plant seed and a cover crop of oat seed.
This area has been slower to take and Barbara’s keen eye IDs the mugwort as it pops up and she pulls it up right away.
I won’t get into the chemical debate; both sides make honorable arguments and the variables for good decision-making are many.
When it comes to chemical eradication of weeds, I will stress that common sense and adherence to best practices is key to minimize animal harm and habitat contamination and keep humans safe. Also, as I finish up this column, an opinion piece from Dana Milbank in The Washington Post has hit my inbox.
Anyone trying to make an informed decision should read it — www.washingtonpost.com/opinions/2023/06/30/herbicide- invasive-plants-national-parks-shenandoah/
Dee Salomon “ungardens” in Litchfield County.
