What is this weed and how can I control it?

Asked October 3, 2018, 9:28 AM EDT

This plant is invading my lawn and gardens. It forms a dense mat. Each leaf is rooted, unlike creeping Charlie, which it resembles in miniature. My first photo shows a quarter for scale. It flourishes in full sun and late summer. I don’t recall a problem in the spring, so believe it is an annual. It has no flowers and never gets taller than about an inch; the leaves stay small. Every year it has come back a little worse. When leaves are crushed, the scent is mild and grassy, not minty. Please help?

Howard County Maryland pennywort lawn weed lawn marsh pennywort

6 Responses

The weed looks like it may be a type of pennywort or dollarweed, Hydrocotyle spp.
It is a warm season perennial weed that spreads by seeds, rhizomes, and tubers. Dollarweed thrives in weak, thin turf with excessive moisture. The first defense against dollarweed is to reduce moisture levels and modify cultural methods (i.e., proper mowing height and irrigation).
Here is some information from Clemson on this weed https://hgic.clemson.edu/factsheet/dollarweed/

You will have to make some decisions. In flower beds, you can use a systemic vegetation killer such as glyphosate. This will kill everything. If you have desirable plants you will have to shield them and follow label directions.

In the lawn - if the lawn is over 50% weeds, you will have to consider total lawn renovation. This can be done up until mid October. This includes having your soil tested http://extension.umd.edu/hgic/soils/soil-testing, decide on seed, kill the existing lawn with glyphosate, prepare the site for planting, and seed or install sod. Now is the time for lawn renovation for a cool season grass such as tall fescue. Tall fescue grows best in full sun to partial shade. Fine fescue is recommended if the lawn is mostly shade. Hard fescue is the best choice.
Here is our publication on Lawn Establishment and Renovation see page 7 and our website http://extension.umd.edu/hgic/lawns/lawn-renovation
http://extension.umd.edu/sites/extension.umd.edu/files/_docs/programs/hgic/HGIC_Pubs/lawn_pubs/HG102...
Here is more information from our IPM Report page 3 https://extension.umd.edu/sites/extension.umd.edu/files/_docs/programs/ipmnet/13Oct11L.pdf

If you need to spot treat only, use a post emergent herbicide now and next growing season as soon as you notice the weed to reduce any further growth. You can use a combination herbicide that contains the following broadleaf weed killers: 2,4- D, dicamba, and mecoprop (MCPP) or MCPA. Follow label directions as caution needs to be used around the roots of trees and shrubs.

mh

Thanks for your advice. I am not sure my weed fits this description, which is not to say it isn’t a relative of some kind. The areas where I see it tend to be dry, not wet. The leaf photo on the website you reference is shown below, and I have added another photo of mine showing the underneath side. Mine is almost heart-shaped but scalloped, with the stem at the innermost point, and the leaves never reach more than 1/2” across. I suspect the treatment is the same, so I will proceed on that assumption, just puzzled that I can’t seem to find any references on this exact plant. Thanks again!

Thanks for your advice. I am not sure my weed fits this description, which is not to say it isn’t a relative of some kind. The areas where I see it tend to be dry, not wet. The leaf photo on the website you reference is shown below, and I have added another photo of mine showing the underneath side. Mine is almost heart-shaped but scalloped, with the stem at the innermost point, and the leaves never reach more than 1/2” across. I suspect the treatment is the same, so I will proceed on that assumption, just puzzled that I can’t seem to find any references on this exact plant. Thanks again!

Take a look at the attached link from Maryland Biodiversity. The weed looks like it may be Lawn Marsh pennywort, Hydrocotyle sibthorpioides.
This is an introduced species and there is not a lot of information about it.
https://www.marylandbiodiversity.com/viewSpecies.php?species=2354

mh

Yes, that’s it exactly! If you find more information, please let me know. I will try the steps you recommend. Many, many thanks!