Herbicides That Won’t Kill Daylilies


  • Daylilies are a dependable, easy-care perennial that are tolerant of drought and flooding, immune to heat stress, grow well in sun or shade and thrive in most soil conditions. They range in size from 8 inches to 5 feet, with trumpet-shaped flowers that are 2 to 8 inches long. They are widely used in public landscaping and as groundcover on slopes. Herbicides are chemicals that kill or inhibit growth of plants such as weeds, but also frequently damage nearby ornamental plants. There are several solutions to weed problems in a daylily flowerbed.

Pre-Emergent Herbicide

  • Corn gluten meal is a by-product of the corn milling process. It was developed and patented in 1991 by Dr. Nick Christians at Iowa State University as a pre-emergent herbicide. It works by inhibiting the germination process of new plants without disturbing the root systems of nearby older plants such as daylilies. Weed seeds germinate but do not form a root to continue growing. It is applied in early spring and fall when weeds naturally germinate, and is effective for four to five weeks after application. Corn gluten meal pre-emergent herbicide has no effect on weeds that have germinated.

Post-Emergent Herbicide

  • Control weeds in an established daylily flowerbed by applying a non-selective herbicide with a wick applicator. There is risk of injury to the daylilies if they absorb the herbicide through leaves or roots. A wick applicator allows exact placement of the herbicide on the weeds and there is no danger of toxic drift. "Once an area has been cleared of weeds, measures should be taken to prevent immediate re-growth," according to the Ohio State University website information on weed control.

Re-Growth Prevention

  • Prevent weed re-growth in the daylily flower bed through the use of mulch made from materials like bark chips, straw, dried leaves and mature compost. Weeds need sunlight to grow and mulch obstructs sunlight from reaching the weed seeds. A 4- to 6-inch layer of mulch around each daylily plant prevents weed growth. Apply the mulch layer in early spring before soil warms up and again in fall to prevent winter annual and perennial weed plant germination.

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