Q: I'm attaching pictures of this weed that has taken over the vegetable garden my kids and I have grown for years. This weed has been getting worse over the past several growing seasons, and we're overrun with it this year. We have tried Preen, mulch and just good old-fashioned weeding. They seem to multiply over night. I have even completely sprayed them with Round-Up in the fall and still they come back. Help! We hate them.
A: Your weedy invader is groundsel, a weed that spreads readily by seeds and has little yellow flower heads.
Round-Up didn't work because it kills the existing plants but does nothing to stop the gazillions of seeds in the soil from germinating. Those just pop up the following year.
Weed-preventers such as Preen normally are more effective against seeding weeds, but this is one that doesn't seem to be fazed by the chemical in Preen and most other weed preventers.
That leaves us with mulching the ground to discourage new sprouting and then pulling young plants as soon as they pop up. At least that's one positive thing -- they do come out easily.
It's really important to yank groundsel before it has a chance to go to seed. If you let them flower and develop those little powder-puff seedheads (similar to dandelions), the plant will resupply itself with thousands of potential new plants with every bloom.
There's not much you can do if birds are bringing in seeds on their wings or if the wind is blowing in groundsel seeds from a neighboring untended lot or weedy neighbor. But at least you can keep your own plants from conspiring against you.
Something else that benefits this weed is tilling your garden at the end (or beginning) of each season. By knocking off the tilling, you avoid stirring up dormant groundsel seeds that are buried and unable to germinate unless they're brought higher up in the soil where it's warmer and lighter.
If you don't till and you can stop any current groundsel plants from seeding or blowing their seeds into your yard, you'll eventually shut off the resupply lines. Eventually, all of the groundsel plants near the surface will germinate and get picked off, essentially bankrupting the seed bank.
I know it's a lot of persistent work, but with this weed, it's the best way to go.