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09/12/2018 07:00 AMSeptember invites fall lawn and garden advice. Soon, articles on bare patch repair, leaf composting, and fall pruning will flutter onto screens and pages like leaves from the trees.
This year, I’m suggesting a less conventional autumn topic: Weeds.
Since July, I’ve barely gone a day without hearing, “I can’t believe the weeds this year.” For reasons that I hope will become clear, the conversation needs to continue.
Indeed, 2018 has produced a bumper crop of these unwanted plants. (The desirable plants had a great year, too.) But why? Most people seem to think it was the rain, but I wasn’t so sure the rainfall was extraordinary.
I asked expert Spencer Aronstein, the lead forecaster and one of four partners at Southern Connecticut Weather, a hyper-local weather site (www.southernconnecticutweather.com). According to Aronstein, the shoreline area had a rather “average” Connecticut summer rainfall as of Aug. 20.
“Since March 1, we’ve seen over 23 inches of precipitation at the Bridgeport airport, compared to a normal total of around 21 inches,” says Aronstein, “and at the Groton airport we’ve seen over 20 inches of precipitation, which is right around normal.”
Why do people feel like it’s raining all the time? If the amount of rain isn’t extraordinary, maybe it’s the rollercoaster pattern.
According to Aronstein, “April, June, and July were noticeably above normal for rainfall, and only May was noticeably below.”
Furthermore, Aronstein says the summer of 2017 was the driest recorded at Bridgeport airport in the past decade. And I remember serious drought in fall 2016, not to mention various summers before that. Memories influence perception.
So if the rain was relatively normal, why did 2018 produce a bumper crop of weeds?
Weed scientist Jatinder Aulakh at the Connecticut Agricultural Experiment Station in Windsor points out a different climate dynamic that may explain.
More Seed Production, Earlier
“This year, some late-emerging weeds such as foxtails, crabgrass, and fall panicum may have benefited by a combination of higher Growing Degree Days and wet weather,” Aulakh says.
He also mentions goosegrass, purslane, lambsquarters, ragweed, redroot pigweed, hairy galinsoga, horseweed, and velvetleaf.
Growing Degree Days (GDD) may be an unfamiliar term, but perhaps you’ve heard of another weather index, Heating Degree Days, in the context of home heating. GDD is a cumulative measure, usually tracked during our March 1 to Oct. 30 growing season, which helps growers time planting and harvests, and also helps them fight insects and diseases.
“Rapid accumulation of GDDs results in rapid plant progression,” says Aulakh. “It can lead to early seedling emergence, fast vegetative growth, higher leaf area index, [and] early flowering, seed set, and maturity.”
Weeds are affected the same as all plants.
The Connecticut Agricultural Experiment Station (CAES)’s Lockwood Farm in New Haven has tracked GDD for decades and publishes the numbers and more detailed definitions on its website. (Visit www.ct.gov/caes and search for “growing degree days.”)
Here’s the bottom line: By mid-summer 2018, we had already experienced very high GDD. As of Aug. 29, we have more GDDs than the area experienced at this time last year. We have also experienced more GDDs than the entire 2001 growing season, a full two months before the end of the season.
Go for Crispy Brown
According to CAES’s Jatinder Aulakh, this kind of weather leads to more seed production, earlier. That increase goes into our “embedded seed bank,” the viable seeds that wait in the soil for the opportunity to germinate. Some can wait for many years. For weeds that have escaped from agricultural fields, that means even more challenging weed conditions—both for farmers and for the rest of us.
Let’s go back to the original point: This fall, we need to fight weeds.
Cut them, smother them, pull them out to stop seed production and dispersal. If you cut or pull, do the world a favor: Dry them in the sun until they are crispy brown before trashing them. Some weeds can regrow from stems, leaves, or roots for a surprisingly long time. (Think bittersweet, mugwort, or Japanese knotweed.)
If you are composting on site, cover them with tarps, cardboard, or thick layers of newsprint. (That keeps birds from eating the seeds, or airborne seeds from blowing around.)
Another method is flame-weeding, but use it only if two people can work together, one with an active hose at the ready. A quick Internet search on this topic will produce lots of good safety practices.
The Connecticut Invasive Plant Working Group will hold a one-day conference on Thursday, Oct. 4. To learn more and register, visit cipwg.uconn.edu.
Do yourself (and the region) a favor: Get ready for 2019 by fighting the weeds of 2018.
Kathy Connolly writes on landscapes, land care, and horticulture. See her speaking schedule, and contact her, at www.SpeakingofLandscapes.com.