Love me tender

James Romer, Iowa Master Gardener Coordinator at Iowa State University Extension, offers the following on tender perennials:

Tender perennials are an integral part of many home landscapes in the Midwest. Most have a long blooming period and put on excellent displays of color until it freezes in the fall. The biggest problem with tender perennials is that they will not survive Iowa’s harsh winter weather if left outdoors. The following tender perennials should be dug in the fall and stored indoors until spring graces our doorsteps once again.

Tuberous begonias (Begonia xtuberhybrida) come in a wide assortment of colors and types. Some of the flower forms include camellia, cascade, carnation, picotee and non-stop series. Container-grown plants can be brought indoors for winter enjoyment. Those tubers left outside should be dug after a killing frost. To properly condition the tubers for storage, place them in a warm, dry location for approximately two weeks. Then bury the tubers in a box or sack filled with sphagnum moss or vermiculite. Store them in a cool, dry location.

Caladium (Caladium xhortulanum) is a great plant in the shade. The caladium is grown for its colorful foliage rather than its flowers. When the foliage dies back in the fall, carefully lift the tubers out of the soil and find a warm, dry place to cure them. Typically the process is complete in two weeks. Store the tubers in dry sand, vermiculite or sphagnum moss in a cool (50 F), frost-free area.

Gladiolus (Gladiolus hybrids) is stunning in the garden and in arrangements, but they need to be dug and tucked away for the winter months. The gladiolus or glad develops from a growing structure called a corm. A corm is a short, thickened underground stem where food is stored. When the foliage has yellowed, lift the corms carefully, cut off the foliage 1 to 2 inches above the corm and allow drying for a week in a sunny location. Corms can be treated with a fungicide to prevent disease while in storage. Remove and discard the remains of the old mother corm located at the bottom of the large, healthy corm. Place the corms in old onion sacks or nylon stockings. Then store the corms in a cool, dry, frost-free location until spring planting occurs.

Though calla lilies (Zandedeschia spp.) are tropical in appearance, they can be successfully grown in the Midwest. After the foliage has been damaged by a frost, cut off the tops about 2 inches above the soil line. Dry the calla rhizomes in a warm, dry location for one or two weeks. Bury the rhizomes in vermiculite, sawdust or peat moss, and store in a cool (45 to 55 F), frost-free area.

The large, banana-like foliage of the canna (Canna xgeneralis) stands out in the garden. Some can get to be about six feet in height, while others top the two to three-foot range. After a killing frost, cut the stems back to about 3-4 inches above the soil. Carefully dig up the rhizomes, let them dry for a few hours, and then place them in crates or mesh bags. Store at 35 to 45 F.

Dahlias (Dahlia hybrids) stand out like beacons in the summer garden. With more than 40,000 varieties to choose from, it’s difficult to not like at least one. After a killing frost has destroyed the foliage, the top of the dahlia should be cut away, and the tubers should be carefully dug and labeled with the variety name. Wash the tubers with water to remove as much soil as possible. This lessens the chance for soil insects to destroy the tubers while in storage. Dry the tubers in a site protected from strong winds and out of direct sunlight. When the tubers become dry to the touch, remove any portion of the stalk that remains and place the tubers upside down in vermiculite to ensure that any water in the remaining crown tissue drains out.

Although all of these plants require more work to keep than your average perennial, their attractive flowers and foliage are well worth the extra effort.

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