September
2006
By
B. Rosie Lerner
Extension Consumer Horticulturist
Purdue University
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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 deg. 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 deg. 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 deg. 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
deg. 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 deg. 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 deg. F.
9-21-06
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