University of Maryland: Garden Q & A
Q: A flat patch of something with yellow flowers is spreading more and more in a woodsy area. The flowers have eight buttercup yellow petals, not cupped. Leaves are glossy green. I’m afraid this stuff will take over my woods.
A: It will. You have lesser celandine, a non-native invasive flower forming impenetrable mats which overrun native species.
It greens up very early in spring, then goes dormant by June. Its small bulblets or tubers easily break off the roots to start new plants.
If you try to dig it up, shovel up the whole clump including the soil to be sure you get every bulblet. Any systemic herbicide containing glyphosate works well on the solid mats.
Q: What vegetables can I plant outside while the ground is still cold? Will frost kill them?
A: You can still plant a slew of vegetables that like cool temperatures, such as carrots, beets, lettuce, potatoes, radishes, and Swiss chard.
For more options, see the new planting calendar on our HGIC website: http://www.growit.umd.edu/GE007_Vegetable_Planting_Calendar_for_Central_MD.pdf .
If a hard freeze is predicted, you can protect them by throwing on row cover or a sheet, or placing cardboard boxes over the plants.