When you buy mums and asters for fall display, choose plants whose flower buds are just beginning to open so the color will last longer in your garden.
Generally mums and asters will last for 4-6 weeks depending on weather conditions. Season-extender mums that will be available later in the season can keep color going through October and sometimes later, depending on weather.
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If you plan to plant mums into a shady site, it is best to wait until the flowers are open before planting. If the mums still are tight in bud when they are planted in shade, the flowers may not open.
Pansies typically will not develop much in the autumn season, so it is best to buy large plants that are in full flower to install in your garden. Plant them close together for a better show.
August and early September were on the dry side with some warm temperatures, so provide supplemental water as needed to any new plants you have installed over the last two to three years.
Newly planted evergreens are particularly in need of watering so that they do not go into winter dry. Evergreens continue to lose water through their leaves during the winter. They are less likely to sustain winter burn if they have plenty of water in their tissues and in the soil around their roots when winter arrives.
Be sure to make notes about any changes you have thought about making to your garden now. It is easy to forget these observations over late fall and winter. Keeping good notes will make you more efficient and your garden better looking.
Have your garden soil tested to determine how best to manage it and what fertilizers to use.
A soil test in fall will confirm the status of your garden soil and help you craft a management plan for your garden soil next year.
Make a composite sample from a few areas in a garden bed and send them in for testing. If your garden is large it is a good idea to break the garden into zones and test each of them. To find a soil testing laboratory, see the website of the University of Illinois Extension at urbanext.illinois.edu/soiltest. Soil tests also can be arranged through some garden centers.
If your soil is typical of the Chicago area, a test will show it to have adequate phosphorus. Choose fertilizers that have little or no phosphorus.
• Tim Johnson is director of horticulture at Chicago Botanic Garden, chicagobotanic.org.