Ammannia coccinea

Scarlet Ammannia is an annual with simple or branched stems, which are 5-40 cm high. The glabrous leaves are strap-shaped, 2-4 cm long, and seem to join together opposite each other on the stem. 1-5 inconspicuous flowers occur at the base of the leaves. Each flower is only 2-3 mm long with a globose ovary tightly surrounded by a shallow 4-5-lobed calyx and inconspicuous purplish petals, which are sometimes absent. The 4 stamens project slightly above the mouth of the flower. The fruit is a nearly round capsule.

This species is similar to its close relative, ROTALA RAMOSIOR, but the latter has leaves with short petioles and only one flower per leaf. Many species of EPILOBIUM have opposite leaves, 4-parted flowers and occur in wet sites; however, their petals and sepals are borne on top of the ovary rather than surrounding it, and the fruits are long and slender. GRATIOLA, BACOPA, and VERONICA all have opposite leaves, but their flowers are larger and have a united corolla. A hand lens may be necessary for positive identification.