Handle This Spinach With Care
Untreated water spinach cuttings quickly regenerate roots when placed in water.
A small Asian plant with an innocent-sounding name has turned itself into
the culinary pest of the Florida Everglades.
"Water spinach is a very invasive and aggressive plant," says
biologist Robert Kipker, who is with Florida's Department of Environmental
"It crowds out native plants and in some countries, damages rice and
sugar crops. What's worse, herbicides approved for use in Florida's aquatic
environment aren't effective against water spinach."
All the water spinach plants that have been found in Florida's waterways are
likely escapees from home gardens or illicit growing plots, according to
The first historical record of cultivated water spinach, Ipomoea
aquatica, comes from the Chin Dynasty around A.D. 300. Originating in India
and Southeast Asia, the plant is rich in iron, making it an ancient remedy for
anemia. So people emigrating from those Asian regions understandably wanted to
take this nutritious vegetable along for use in traditional recipes.
In the Sunshine State, people grow leftover stems--sometimes purchased
illegally--in backyard waterways. If just a little of the rooted plant escapes
from the home garden, water spinach can grow explosively. That's what state
officials must prevent.
"There are many proposals for keeping this plant from doing what it
loves to do best--taking root and spreading," says Kipker. "Freezing
or canning it has been suggested, but it's the fresh product people like."
So plant physiologist Thai K. Van, who is with USDA'sAgricultural Research Service, and plant
scientist Suzanne Cady, who is with the Hillsborough County Extension Service
at the University of Florida, have checked out a different option: irradiation.
They discovered that irradiating water spinach prevents the plant from
taking root, should a gardener get the notion to try it. One-half kiloGray is
all it takes, according to Van. He works in ARS' Aquatic Weed Research Unit at
"A kiloGray is a unit of absorbed radiation energy," says Van.
"The Food and Drug Administration allows up to 1 kiloGray of irradiation
to delay ripening in fruits and vegetables and to control insects, mites, and
other pests in food.
The spice industry currently uses irradiation to prevent spoilage of its
products. "But," says Kipker, "if we choose the irradiation
option, we have to be confident that the plant is not viable."
Water spinach cuttings exposed to 0.25 kilograys of cobalt radiation show no
Van is completing more tests to confirm earlier results that 100 percent
root inhibition occurs at one-half kiloGray. In this study, he will also test
the effect of the procedure on flavor quality.
The work could have an even bigger impact, since a change in Florida law is
being considered. Under it, private families still couldn't grow water spinach,
but farmers with the right expertise would be allowed to grow it for
When Florida's DEP found 50 acres of commercial water spinach in production
outside of Tampa in 1995, it was seen as time for change. So a new strategy was
developed with the help of the state agriculture department. Its goal was to
have the crop raised in a tightly quarantined setting by growers who could
Now water spinach growers can obtain a special license after first proving
they can grow the crop to state specifications. This means isolating the crop
from Everglades tributaries, carefully disposing of plant waste, and
surrounding the growing area with a 15-foot buffer zone. Officials from the
Florida Department of Agriculture monitor the farms for compliance.
If Van can show his irradiation technique will render the water spinach
nonviable, licensed farmers might also be allowed to sell their crop to Florida
families one day. There already is an irradiation facility in the state that
could conceivably treat the spinach. Then the challenge would be shipping the
product safely from the farm to the irradiation plant. --By
Jill Lee, Agricultural Research
Service Information Staff.
Thai K. Van is in the
DA-ARS Aquatic Weed Research Unit, 3205 College Ave., Fort Lauderdale, FL
33314; phone (954) 475-0541, fax (954) 476-9169.
"Handle This Spinach With Care" was published in the June
1998 issue of Agricultural Research magazine. Click
here to see this issue's table of