Next loosestrife is already loose.

Water gardeners and aquarium enthusiasts need to be warned about recent escapees from their creations that menace wild wetlands, says a Florida botanist.

Rotala rotundifolia turned up uninvited last year in a northern Alabama pond, and it's moving into Florida canals, according to Kathleen Burks of the Florida Department of Environmental Protection in Tallahassee. It belongs to the same family as the notoriously invasive purple loosestrife, which is choking out natives on stream banks across the country. The new Rotala, originally from Asia, grows lush bands of foliage along the water's edge, blooms in swaths of pink spikes, and also thrives underwater. Aquarists treasure the plant's rosy foliage, and aquarium dumping probably loosed it on North America, says Burks.

The snowflake or crested floating-heart (Nymphoides cristata), which arrived from Asia in the past 6 years, is also spreading through Florida. Its heart-shaped leaves float on the water surface and five-petaled white flowers rise on little stalks above the leaves. A white ruffle lining the middle of each petal distinguishes the plant from the two natives in the same genus. The introduced species may look just as lovely, but Burks says it quickly covers the water surface with a canopy of its leaves and shades out the native plants underneath.--S. M.