Plants: Beautiful Nuisance

Flowered spikes of lavender blossoms give the water hyacinth a distinctly delicate air. But no aquatic plant is healthier or hardier. Few multiply as fast; in the summer months in the tropics, the hyacinth doubles its number once every 30 days. The plant is so prolific that once it takes hold, floating carpets choke rivers, canals, lakes and bayous. It hinders boat traffic and uses up oxygen needed by fish. After years of trying to keep the hyacinth at bay, a group of weed-control experts and navigation engineers—the Hyacinth Control Society—met in Palm Beach to discuss their few successes and many failures with the beautiful nuisance.

Although the tangled weed abounds in nearly every tropical and subtropical part of the world, the scientists reported, it can be as unpredictable as it is prolific. It sometimes grows below a dam but not above it. In some places, once destroyed, the plant does not grow back; in most other places, it returns as tough as ever. On the Nile, where Egypt spends $1,500,000 annually on hyacinth eradication with dredges and herbicides, the plants cluster to form islands strong enough to support animals. “You can never let up,” says William E. Wunderlich, aquatic growth control chief of the New Orleans District of the Army’s Corps of Engineers. “I’ve seen a 300-h.p. tug stopped tight by water hyacinth. I’ve seen grown men walking on it.”

In the U.S., the water hyacinth has been brought partially under control with the familiar chemical 2,4-D. But 2,4-D may harm surrounding vegetation and is expensive to apply. The manatee, a clumsy, seal-like sea cow with a voracious appetite for hyacinths, has proved a devastating enemy to the plant. Manatees have been placed in bodies of water as a kind of marine lawnmower. They, too, have a drawback: they are listless lovers and slow to reproduce. Two of the sea cows were kept in the same tank for two years. They have no progeny to show for their long affair.

For all the trouble the hyacinth causes, cautioned Oxford Botanist Dr. E.C.S. Little, a member of Britain’s Weed Research Organization, the plant is not all bad. It could be harvested, he said, as a new source of food; it has about the same nutritional value as the turnip. Little need have little fear that the plant will be wiped out. It once grew only in fresh water, but in Louisiana it now grows in salt marshes, has even lived for a while out in the Gulf of Mexico. It may soon be attacking tropical ports all over the world.