Agapanthus, commonly called lily of the Nile, comes from South Africa, not the River Nile region. Beloved by birds, hummingbirds and bees but not every gardener, this heat-loving plant produces flowers in white, purple and blue. Lily of the Nile grows in U.S. Department of Agriculture plant hardiness zones 6 through 10, depending on the species. All parts of the plant are poisonous. Atrazine herbicide, which is used on certain lawn grasses to kill weeds, may eliminate problem lily of the Nile plants.
Atrazine is widely used on food crops in the U.S., though it is banned in some European countries. It can also be used on certain species of lawn grasses to control weeds. It works on both broad leaf weeds and grassy weeds. The herbicide disrupts photosynthesis of target plants, causing them to starve to death.
When and Where to Apply Atrazine
Herbicides containing atrazine should be used when the lily of the Nile plants are actively growing, but only if the temperature is below 90 degrees Fahrenheit. Atrazine pollutes water supplies, so avoid using this herbicide near streams, rivers, ponds or other water sources. Atrazine herbicides are safe to use on St. Augustine grass (Stenotaphrum secundatum), which grows in USDA zones 8 through 10; and centipede grass (Eremochloa ophiuroides), which grows in USDA zones 7 through 10. The product may harm other grasses and should not be used where it can drift onto desirable plants.
Prepping for the Kill
Lily of the Nile leaves may be slender and grasslike, but they are far from fragile, and the plant itself is tough, surviving drought, heat and brief periods of cold. Because lily of the Nile can reproduce through underground rhizomes or by seeds, using herbicides alone may be ineffective. A New Zealand government website recommends cutting off the flowers and bagging them quickly to keep seeds from dropping on the ground. The site also states that cutting the plants down or wounding the foliage before spraying or slathering on herbicides like atrazine enables the poison to penetrate the plant more effectively.
How to Apply Atrazine
The Environmental Protection Agency limits atrazine herbicide on lawns to no more than 8.6 ounces per 1,000 square feet of lawn, divided into two applications per year. Atrazine may be applied in early spring, before or just as lily of the Nile or other weeds are ready to sprout. Lawns riddled with lily of the Nile may also be sprayed while the grass is dormant. Using a ready-to-use atrazine formula, it is best to start at the far end of the lawn and work your way back, spraying as you go. Coat the lawn, but not to the point of runoff. For individual plants, prepare for spraying as above, and focus the atrazine spray on the stump of the stem or center of the plant. More than one application may be necessary to kill the lily of the Nile. You can also "paint" individual plants with liquid herbicide to cover them fully with no risk to nearby, desirable plants. When using atrazine concentrate, 5.1 teaspoons of herbicide mixed with 1 quart of water will treat 100 square feet of lawn. To treat 500 square feet, mix 4.3 ounces of herbicide into 1 gallon of water and apply it with a garden sprayer. Wear gloves, long sleeves, long pants and shoes when spraying any chemical. Safety glasses are also a good idea. Keep children and pets out of the treated area until it dries.
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