SEPTEMBER
2006

 

 

 

By
B. Rosie Lerner
 
Purdue Extension
Consumer
Horticulturist

 

 

 

 

 

9-21-06

Tender Perennials Need Indoor Protection

Most gardeners think about planting bulbs this time of year rather than digging them up. But some flowering perennials are not hardy enough for our climate and must be lifted from the soil and their bulbs, roots or other underground structures stored indoors over winter. The most common garden plants in this category include gladiolus, caladium, tuberous begonias, canna and dahlia. Although these plants are all considered tender, each is best handled a bit differently for winter storage.

Caladiums, often called elephant ears, are quite sensitive to cold temperatures, so their tubers, (like small potatoes) should be dug just before frost. Place the tubers in a warm location for 7-10 days to remove surface moisture. To prevent excessive drying in storage, pack the tubers between layers of dry vermiculite, peat moss, sawdust or similar material in a strong box. The optimum storage temperature for caladiums is 60 F.

Tuberous begonias should also be dug just before frost. Cut the tops back to 2 inches and air dry the roots for two to three weeks in a warm location. Then, store in boxes, as you would caladiums, but decrease the temperature to about 45-50 F.

Dahlias should be cut back to about 3-4 inches after the first light frost. Then, carefully lift the plants, leaving as much soil attached as possible to prevent breaking the fleshy roots. Because they are so susceptible to drying, dahlia roots should be air-dried for only a few hours or so. Then, pack in boxes, as you would caladiums, and store at 35-40 F.

Gladiolus produces underground, compressed-stem structures called corms, which should be dug when the foliage just begins to fade, usually after a frost. Use a spading fork to carefully lift the plants and save any of the little miniature corms (called cormels). These cormels will grow larger, if planted next year, and eventually reach a size that will support flowers as well as foliage.

The corms should be cured before storing to help prevent disease from developing. Cure the corms for two to four weeks in a warm (about 75-80 F) room where air can circulate around the corms. Once cured, the corms should be stored dry in a cold, but non-freezing, location, about 35-40 F. Old nylon stockings or onion bags hung from the wall allow good air circulation throughout storage.

Canna need not be dug until after a hard frost. Cut the tops back to 4 inches, lift with a spading fork and air dry in a warm spot for 1-2 weeks. Canna roots do not require covering; they can simply be placed in shallow boxes. The roots are best stored at 45-50 F.

 

Writer: B. Rosie Lerner
Editor: Olivia Maddox