PlantFiles: Mexican Clover, Tropical Mexican Clover
Richardia brasiliensis

This is a major weed in my garden as well. In addition to its prolific seeding, it produces a deep taproot, and will resprout from broken pieces of taproot left in the ground when the plant is pulled. It could be considered an attractive groundcover in a cooler climate, perhaps, but is just too invasive for garden use in central Florida.

10 worst weeds in my garden (sandy soil, dry to wet, zone 9b):
Bidens alba var. radiata
Richardia brasiliensis
Panicum repens
Ambrosia artemisiifolia
Paspalum urvillei
Centella asiatica
Digitaria ciliaris
Schinus terebinthifolius
Phyllanthus amarus
Commelina diffusa

Weed in tropical areas. I have to pick up new seedlings that pop out on my garden every day, but it is useless as there are thousands of other plants producing seeds on the surroundings.

This is a low ground-cover type plant, that grows naturally on my property south of San Antonio, TX. It has a very nice bright green color to it and petite small white flowers, and grows easily in rocky/sandy soil and dry climates. It can be transplanted, if delicately done, before it starts spreading out too much. I have planted in a small corner garden near my front porch along with my Purple Heart plants. The two ground covers complement each other nicely for now... although I've been reading that the purple heart may take over.
This clover is very hardy and looks almost like it retains moisture in its stems and such like a cactus would, as it appears fresh and almost moist even when the temperatures are sky-high in our Texas summers and there has been no water for days!