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Schmidt: Fall perennial and bulb care

By Staff | Oct 13, 2017

Digging and Storing Tender Bulbs

Many of the tender flower bulbs such as gladiolus, cannas, dahlias and tuberous begonias require special care to assure good condition the following spring.

Gladiolus are one of the most common types of tender bulbs gardeners overwinter. Dig the bulb (corm) after the first frost and cut the tops off flush with the top of the corm. Spread the bulbs in a dry, frost free place for 2-3 weeks. After curing, the old shriveled corms and roots should snap off cleanly. Those that do not clean readily are either insufficiently cured or diseased, the later is often detected by discoloration of the husks. After cleaning, dust the bulbs by shaking in a paper bag with 5% Sevin Dust (1-2 teaspoons for each 100 corms). Then store in shallow boxes on a basement floor or on low shelves.

After a frost, the dahlia, canna, and tuberous begonia root clumps should be carefully lifted with a spading fork. Shake off the greater part of the soil and cut off the tops at ground level. Tuberous begonia tops should be removed close to the tuber. Dry the clump well but not to the point that any shriveling of the roots is noticed. Place the cured clump in a large plastic bag (without holes) and tie securely. Do not divide the clump until next spring.Store in the coolest, frost-free place that you have in your home (34-40 degrees is ideal). Inspect occasionally for signs of mold, which may occur, if drying was insufficient. If mold occurs, open the bag temporarily and allow the drying.

Fall Care of Perennials

Most of perennials should not be cut back for the winter. Leaving the tops on until spring helps hold snow and protects the plants’ crowns for the winter. Other reasons to leave perennial foliage standing is to provide habitat for native pollinator species to overwinter and the seed heads provide a good winter food source for birds.

However, some perennials such as peonies and iris benefit from being cut down in late fall. This is because they tend to be more susceptible to foliage diseases. Peony stalks are cut down just below soil level to reduce the amount of blight fungus which overwinters. Iris are cut back because they are very susceptible to rot in the spring from wet soil.

Some gardeners don’t like to see standing perennials in the winter so cutting back perennials is often done for the visual appeal preferences of the gardener. When perennials are cut down, it is best done after they have gone dormant. This is usually after the plants have experienced several hard frosts. Cut the plants down to within 2-3 inches of the crown. Cutting too close can result in winter injury on some perennials. This is because the buds for next year’s growth are right at the surface or higher and not below the soil line.

Adapted from Todd Weinmann, NDSU Extension Horticulturist & University of Illinois Extension

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