Helps to 'know your enemy' with runaway weeds ~By AMY IVY, Cornell Cooperative Extension
Preventing weeds in the first place is, of course, the best course of action but I’ll get to the reality of runaway weeds, too.
First, it helps to understand how weeds grow and succeed so well. Just as I say when managing bugs and diseases, it really helps to "know your enemy" to be able to choose the best course of action to deal with them.
Annual weeds are those that reproduce mostly from seed, and the individual plant dies after setting those seeds. For these weeds, preventing them from flowering is a key strategy. I realize this is often easier said than done, but that’s your goal. This group includes lambsquarters, redroot pigweed, crabgrass and galinsoga.
Biennial weeds are those that produce leaves the first year (usually as a low-growing rosette), and then a tall flower stalk and seeds the second year, and then they die. This group includes Queen Anne’s lace, wild parsnip and garlic mustard.
Perennial weeds live year after year, flowering and producing seeds each year. This group includes dandelion, quackgrass, ground ivy or creeping Charley, thistle and plantain. Some members of this group, most notably quackgrass and ground ivy, reproduce not only from seed but from pieces of the root or stem as well.
The key to preventing weeds is to remove all the weeds you can see, then mulch to prevent the seeds in the soil from sprouting.
Mulch will also discourage blown-in seeds from sprouting to some degree, but many seeds sprout just fine in the mulch layer. They are easy to pull out of the mulch when young, so be diligent to get them early.
By midsummer, though, most gardeners are probably coping with the weeds that got away; I know this gardener certainly is. Here is where knowing whether it’s an annual or perennial can save you some work.
Annual weeds are going to die anyway, so all you really have to do right now is cut them down so their flowers can’t produce seeds.
I still plan to yank out the annual weeds scattered throughout my flower garden, but I may just mow them in my larger vegetable garden. Once mowed, I’ll add another layer of mulch to smother their bases.
But perennial weeds need more than this. They survive the winter by storing food in their extensive root systems so they can easily tolerate mowing or being cut back. Here you need to tackle the root.
For plants with a long tap root, like dandelions, you need to dig down to get as much of that storage root out as possible. For plants with extensive, far-reaching roots and rhizomes like quackgrass, you need to tease out as much of those white rhizomes as possible.
If you’re feeling overwhelmed, here’s an emergency approach to take right now. Clip or mow off any weeds in flower and put mulch over any bare areas. Then wait until just after a rainy spell to tackle the perennial roots; they’re much easier to remove when the soil is moist. You can even wait until early fall to tackle them, but the sooner, the better.
Amy Ivy is a regional vegetable specialist with the Eastern NY Commercial Horticulture Program of Cornell Cooperative Extension. Home gardening questions are handled by each county’s Cornell Cooperative Extension office. Office numbers are: Clinton County, 561-7450; Essex County, 962-4810; and Franklin County, 483-7403.