Lindernia microcalyx Is not native to the United States. It is included here as an aid to identification and not to promote its cultivation.
Lindernia microcalyx Pennell & Stehl is an annual or short-lived perennial native to the tropics of North and South America. I found it growing in a somewhat disturbed wet area in Martin County many years ago; however, I did not send voucher specimens to any herbariums so it is not officially listed as an introduced species occurring outside of cultivation in Florida. It is distressingly similar to the native Lindernia grandiflora in its sprawling stems that root wherever they touch moist soil, in its rounded leaves, and showy flowers. It differs in having (1) minutely glandular hairy sepals; (2) thickened pedicels, often noticeably thicker just below the seed capsule; (3) flowers self-fertile with every flower setting a seed capsule, even in isolated plants; and (4) subglobose seed capsules about 2 millimeters long. In contrast, the native Lindernia grandiflora has non-glandular, hairless sepals; filiform pedicels of uniform thickness; usually self-sterile flowers with isolated, solitary plants rarely setting seeds; and seed capsules 4–5 millimeters long.