Overwintering
Tropicals
If you grew a few tropical plants in your garden this summer
and want to try your hand at keeping them alive indoors until
next spring, you have three options:
1. Keep the plant in active growth in a warm, sunny place (like
a sunroom or heated greenhouse).
2. Take cuttings and allow the "mother" plant to die.
Root the cuttings and pot them up so you have new plants in the
spring.
3. Allow the plant to go dormant and keep it in a cool, dark
place until spring.
Overwintering Techniques
Overwinter as houseplants: cordyline, phormium, palms, croton,
bamboo, jasmine, allamanda, bougainvillea, hibiscus, citrus
Keep plant dormant in a cool, dark place: brugmansia, banana,
dwarf canna
Store dormant bulbs/corms/tubers: ginger, sweet potato vine,
colocasia, caladium, canna, calla, dalia
1. Keeping Your Plants In Growth Mode
If you have a sunny window where the air temperature stays about
60-70 degrees, you can keep most tropicals growing and possibly
even blooming right through the winter. Bougainvillea, jasmine,
citrus, hibiscus and geraniums are some of the plants that will
be happy in this situation, as long as they get plenty of light,
and nighttime temperatures don't drop below 40 degrees. Plants
that are relatively small will be happy to spend the winter under
a grow light. Set a timer to ensure they get about 12 hours of
light each day.
Make sure to bring these plants into your house or sunroom before
the weather turns cold and definitely before frost threatens.
Expect that the plants will drop some leaves the first few months
as they adjust to living indoors. Water as needed, but keep the
soil on the dry side. Avoid crowding, because good air circulation
will help deter pest and disease problems (try running a small
oscillating fan for several hours each day). If possible, keep
the humidity level between 30 and 45 percent by misting or placing
a pan of water among the plants. In cold climates, keep the humidity
below 30 percent to avoid condensation on your windows.
Keep in mind that the ideal winter environment for most of these
tropical plants would be approximately 50 degrees at night and
65 degrees during the day. Warmer air temperatures can lead to
leggy growth and bug problems. Whiteflies, spider mites and scale
are the most common indoor pests. Check your plants weekly. If
you stay on top of the situation, pests can usually be controlled
quite easily with insecticidal soap. For serious infestations,
dunk the foliage in a dishpan filled with water and a teaspoon
of liquid dishwashing detergent. You can also stick large plants
right in the shower. Let the foiage dry and then douse with insecticidal
soap.
Tropical plants that go through the winter in fairly active growth
usually benefit from being pruned at least once or twice. This
will re-balance the foliage to root mass ratio and will also give
you the opportunity to root some new cuttings. Coleus, plectranthus
and geraniums respond well to this treatment. When spring comes,
repot the plants and start fertilizing with a time-release or
water-soluble fertilizer.
2. Taking Cuttings
Herbaceous, soft-stemmed tropicals such as plectranthus, coleus
and geraniums, can be difficult to overwinter. A good option is
to take cuttings in the fall and let the "mother" plant
die. Root the cuttings in water on a windowsill. Be sure to root
succulent, young stems—not stems that have become tough
or woody. Put only the stem—no leaves—in the water.
Once roots have developed, plant each cuttings in a 3- or 4-inch
pot and keep them on a windowsill or under lights. Fertilize regularly.
You'll have a whole batch of new plants for your spring garden,
and will be a popular guest at next year's plant swaps!
3. Managing Winter Dormancy
Some tropicals do best with—or may even require—a
winter rest. How you care for these plants over the winter depends
on the kind of space you have available, and whether the plants
are soft-stemmed, woody, or bulb-like. Tropical plants that grow
from bulbs or tubers, such as elephant ears, caladium, sweet potato
vine and canna lily, should get nipped by frost before they're
brought indoors. This sends the plant a clear message that the
end of the season has come. At this point you can do one of two
things. You can leave the plants right in their pots over the
winter, keeping the soil barely moist, and store the whole pot
in a cool, dark place. Or, you can trim off the stems, dig up
the bulbs, label them, wrap individually in slightly moistened
newspaper or peat moss, place them in a black plastic garbage
bag and store a cool, dark place. In either case, it is important
that air temperatures remain at about 40 to 50 degrees F. Check
the bulbs monthly to make sure they are still firm and solid.
If they are drying out, mist the storage material around them
with a little water. When spring arrives, repot the bulbs, begin
fertilizing regularly, and put the plant in a sunny window.
Woody-stemmed tropicals, such as jasmine, brugmansia, tibouchina
and bananas, should be brought indoors before the first frost.
Let the plants rest in a cool place (40 to 50 degrees F) with
little or no light—they'll get the message that winter has
arrived and their leaves will gradually yellow and drop. The plants
can then spend the winter in an unheated basement, root cellar,
unheated garage, or even a cool closet. Make sure the area is
relatively dark (try enclosing the whole pot loosely inside a
heavy black trash bag) and that the air temperature stays above
freezing. In most cases, woody-stemmed tropicals should not be
cut back until early spring (unless you can't fit them into the
house!). Water the plants sparingly throughout the winter, checking
monthly to see that the soil is barely moist. When early spring
arrives, revive the plants by repotting them in fresh soil. Water
thoroughly and provide a weak dose of liquid fertilizer. Expose
the plants to bright, filtered light, gradually acclimating them
to full sun. Try to give them about a month of indoor (or greenhouse)
growing time before moving them outdoors.
When it comes to reintroducing heat-loving tropicals to the outdoors,
always do it slowly. Shield them from direct sunlight and wind
for at least a week or two. If the plants are acclimated slowly,
they'll slide right into active growth. Too much early spring
stress will stunt the plant's growth—or even kill it.
The truth is, overwintering tropical plants involves a bit of
trial and error. A technique that works well for one type of plant
or in one particular winter environment may not be ideal for another.
Be prepared to lose a few plants.
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