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Johnson County

Research-based Information You Can Trust — Localized for your needs

Johnson County
11811 S. Sunset Drive
Suite 1500
Olathe, KS 66061

Office Hours:

Monday - Friday,
8:30 a.m. - 5 p.m.

(913) 715-7000
(913) 715-7005 fax

Map to our office

K-State Research and Extension is committed to making its services, activities and programs accessible to all participants. Reasonable accommodations for persons with disabilities may be requested by contacting Johnson County Extension at (913)715-7000. Notify staff of accommodation needs as early as possible.

Kansas State University Agricultural Experiment Station and Cooperative Extension Service

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Perennial Flowers


I had the most beautiful chrysanthemum blooms last fall. This spring they all died. What happened?


Chrysanthemums are popular for the great fall color they provide in the garden. Unfortunately, they often do not survive our Kansas City winters. Sometimes well-established plants are lost because of insufficient winter hardiness. The death is the result of the combination of a dry fall and a dry, extremely cold winter. It is advisable to plant mums in the spring to provide ample time for the development of a strong root system. Mums planted in the fall are less likely to survive the winter.

Cutting back mums:

I keep hearing debates about whether it is best to cut back mums in the spring or fall. Which is best?


When to cut back mums in the garden is really a personal decision based upon your gardening style and when you have the time. It does not matter to the plant. Some gardeners like a neat, tidy garden in the winter. Others prefer the natural appearance of plant material that has died back. The most common school of thought is to leave the mum foliage over winter. The stock and old stems help protect the plants from the extremes of winter by collecting leaf litter for mulch and moisture retention. There is a possible risk, however, that cutting mums back in the fall leads to crown rot as moisture travels down the exposed stem.

Pruning clematis:

Last year I planted a couple of clematis that grew and produced a few flowers. The varieties I planted are Jackman and Niobe. Now that another year has rolled around, how do I prune them?


Some varieties of clematises bloom on last season’s growth while others bloom on new growth. When they bloom determines the proper pruning time and extent to prune. If in doubt, do not prune before flowering except to remove dead growth. The varieties you planted bloom on new growth. Prune them hard in late winter or early spring. Begin pruning above a healthy pair of buds located 15 to 30 inches above the soil. Remove all old top growth that didn’t die naturally over the winter. Once established, many of these plants will grow more than 8 feet in one season. Clematises are a nice addition to the garden and will be enjoyed for many years with proper care.


When is the best time to divide hostas?


Hostas can be most successfully divided in either April or early September. When dividing in April, dig the clump just after the shoots emerge and carefully separate the plant. A nice size division will consist of three to five shoots. When dividing in September, either dig the entire plant or a portion of the plant. Separate the clump following natural division points. Take care that each new plant has a good root system. At both times of year, it is best to replant the divisions immediately. Amend the soil with compost to improve the organic matter content of the soil and provide needed nutrients for growth. Water the new plants well. Depending on the variety, hostas may need to be divided every three to five years, and in some cases longer.

Cutting back iris foliage:

I have planted several new irises over the past few years and hope for great blooms in the spring. Some of my friends say to cut the foliage down after flowering; others say to leave it. What is the correct practice?


Iris foliage should not be cut back after flowering. The only recommended time to trim green foliage is when irises are being divided or transplanted. Dead brown foliage can be removed any time. The best time to divide or transplant irises is in late July through early August when they are dormant. 

Dividing peonies:

My mother-in-law has a peony she would like to share with us. When would be the best time to divide the plant, in the spring or fall?


The ideal time to divide or transplant peonies is in the fall between early September and mid October. It is okay to cut into the thick, fleshy roots when digging. However, care must be taken to protect the eyes during the process. The eyes are the growing points for the plant. Replant them about two inches deep, working some compost or manure into the soil. Peonies will tolerate some shade, but prefer full sun. The plants take two to three years to establish in their new home. Peonies are often passed from one generation to the next because they are wonderful plants that thrive for many years.

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Have questions? The Garden Hotline is staffed by trained EMG volunteers and Extension staff who will assist you with questions.

Phone: (913) 715-7050

Email: garden.help@jocogov.org