Questions on: Cosmos
Ron Smith, Horticulturist, NDSU Extension Service
Q: I had a beautiful bed of cosmos and zinnia last summer but in August they developed mildew. I did not compost any of the plants after I removed them. What can I do to prevent this next year? (Fargo, N.D.)
A: Look for mildew-resistant varieties, increase air circulation, don't water as much and pray for lower humidity!
Q: I have cosmos that look beautiful, then suddenly wilt and die. Out of four plants I only have one left. Any ideas why? I am also wondering when and how to divide switch grass. Finally, can you tell me what the difference is between lilies and daylilies? (Hoven, S.D.)
A: The cosmos are probably infected with Verticillium wilt. It's a pathogen in the soil and very hard to control.
You can divide the switch grass best in the early spring when it is dormant.
Lilies grow from bulbs whereas daylilies grow from tubers. The flowers are somewhat similar in appearance (though lily petals are more slender), but the plants are definitely not! Daylily plants look similar to clumps of overgrown large-leaf grasses while lilies look like your typical Easter lily plant, with a central stalk and slender leaves spiraling from it. The different types of lilies are named so because of their various plant characteristics--plant height, flower color, hardiness etc.
You can order lilies and daylilies from most any mail order flower/bulb catalogs, or maybe put in a request to a gardening friend with extra plants. Lily bulbs should be planted in the fall. Daylily tubers can be planted then or in the spring, and the plants can be divided and replanted almost anytime during the growing season.
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