A while ago a gentleman asked me about a weed he had in his lawn that was keeping his new grass from establishing. He described it as having round shiny lily pad-like leaves. I thought for a minute, for there are several that could fit that description.
Ground ivy and Dichondra quickly came to mind, but the more he described it I figured it had to be marsh pennywort (Hydrocotyle umbellate), often called dollar weed. It’s in the carrot family. I don’t know where the dollar weed name came from, but the leaves are round and often about the size of a penny. I guess some might be as large as a silver dollar.
The plant has clusters of small white star-shaped flowers but they are often inconspicuous. As the name implies, this plant thrives in wet areas but often struggles where there’s good drainage. It also performs well in acid soils. Raising soil pH is one way to make it less competitive, if that’s your goal and it usually is.
This is a tough little devil to rid from your property. It propagates by seed. It also spreads by creeping underground stems. Broadleaf herbicides like 2,4-D, dicamba and mecaprop are usually effective, especially on cool-season turf. Some of the triazine herbicides used for growing corn are effective in warm-season turf, like bermudagrass.
Cutting management is important too. If you leave your lawn a little on the long side the weed will be less competitive. Never scalp a lawn and don’t overwater. This short statured weed loves a wet environment and it needs sunlight. This combination makes it a potential problem during initial lawn establishment.
I wandered my yard and found significant quantities in areas of poor drainage. Grass was already thinning in those locations. I spotted significant quantities in the grassed waterways at school too.
So what do we do if we want it gone and don’t want to use chemicals? We can eat it. Dollar weed is edible and could save you a few dollars off your grocery bill.
Some people eat it raw in salads. I think it is a little tough and chewy for that, but it makes a good cooked green. Flavor is quite mild, much like cucumbers. Some people even juice the leaves, but I’ve never been too big on leaf juice.
If you get the urge to partake, make sure no chemicals have been applied to that area. Also, be careful to collect in places that aren’t contaminated by sewage. Many wet spots often are.
I think the best solution to this little carrot relative is a change in land culture and a little tolerance. Water management is important. Don’t waste water and keep areas too wet. Try to provide better drainage to chronically wet places and keep soil pH from becoming too low.
We all like the looks of a closely clipped lawn, but that opens us up to thinning of the turf. That leads to weed problems. For example, St. Augustine grows well in damp places, but it shouldn’t be cut too short.
Ted Manzer teaches agriculture at Northeastern High School (firstname.lastname@example.org).