Q. I have several tall sedum plants that have been established for about 10 years. They seem to grow healthy each year until late summer, early fall. When they begin to bloom, the center of the plant falls. It looks like something was nesting in the middle of the plant, but that is not the case.
A. After several years, the center of sedum plants will show signs of dying out. At this point, you must divide the plant in order to keep the plant vigorous. You can divide sedum in either spring, or after they have bloomed in fall. Sedums do not like wet feet. In fact, too much water, as well as fertilizer, can cause flopping.
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Note, if you are growing Autumn Joy sedum, commonly grown in gardens, they tend to get tall and floppy, even when new in the garden. To prevent this, try pinching or pruning the plant. When they get to about 8 inches tall in the spring, usually around June, cut them back about 4 inches. This helps keep them shorter. They will still bloom, but be less likely to split open in the fall.
• Provided by Mary Boldan, University of Illinois Extension Master Gardener. Send questions to Ask a Master Gardener, c/o Friendship Park Conservatory, 395 W. Algonquin Road, Des Plaines, IL 60016, or via email to firstname.lastname@example.org. The Friendship Park Conservatory Master Gardener Answer Desk is available 9 a.m. to noon Monday, Wednesday and Friday and noon to 3 p.m. Saturday; call (847) 298-3502.