University of Vermont Extension
Department of Plant and Soil Science
Fall
News
Article
TENDER
PERENNIAL PROBLEMS INDOORS
Dr. Leonard Perry, Extension
Professor
University of Vermont
Temperature, and its balance with
light, are the two most important conditions for successful
overwintering of
tender perennials indoors, in addition to proper watering. Your
plants
will show symptoms if these
conditions aren't to their liking, but these may be confused with other
causes,
and once they show these it may be too late!
While perennials are hardy in their native climates, in colder regions
they
may grow as an annual, and so are called "tender perennials."
These
include such plants as coleus, cannas,
geraniums, and sages or salvia.
Even if plants didn't get inside
during fall, but they were left in a protected location, many will
withstand some
cold and some will even withstand some frost.
If they were subjected to such conditions, try cutting back when
bringing into the warmth. If they are
still living, you should see signs of buds or new growth in a week or
two.
If a tender plant you are
overwintering inside is losing its leaves, perhaps it is too cold, or
cool for
too long a period. With high energy
prices, and many turning down thermostats especially at night, such
conditions
are more common. Wilted, pale leaves in
spite of adequate watering is another sign the plant is too cold.
If a
plant such as coleus has lost its
leaves, it may be too late to revive it.
Try moving such plants into a very warm area (above 55 degrees F at
night and in the 70s during the day), and don't water if the soil is at
all
damp.
Other
plants such as lemon verbena and hibiscus normally lose their leaves,
or
"defoliate",
as part of the normal cycle. Others that
were outdoors in sun during summer, when brought indoors to
much lower light in fall, may lose their leaves in the process of
making new
leaves better adapted in their cell structure to the lower light
indoors.
Over and under watering may also
cause plants to lose their leaves. Check
the soil with your finger, an inexpensive soil moisture meter you can
get at
complete garden stores, or look at the surface.
If leaves are falling and the soil feels wet, or is dark, and the pot
is
heavy, it may be too wet. If it feels
dry, is light in color, and the pot is light, it may be too dry.
If
either of these, correct gradually, don't
immediately go to the other extreme.
Check plants in saucers to make sure when watering that the water
doesn't remain in the saucer for more than a half hour. If room,
place
plants on a tray of pebbles
you can moisten when you water. This is
great for houseplants too, allowing the water to drain from pots, and
keeping
humidity higher around the plants. In
general, and if in doubt, keep tender plants indoors on the dry side.
Moisture also is critical for
storing of some summer bulbs. Dahlias
and cannas should be kept moist, while gladiolus should be stored
dry.
Too much of the other for these may cause
them to rot or die overwinter.
Temperatures below freezing may kill them as well, as I've learned in
years past when they were placed too near a cold wall with minimal
heat.
On the other hand, if plants are in
too warm conditions such as next to heater vents or a wood stove, they
may have
elongated and thin leaves with spindly stems.
This is a sign they are getting too much warmth and not enough light.
So
the solution is to move to a cooler location with similar light, or
increase
the light. The latter can be done by
supplemental lighting from lamps.
Portable clamp-on light fixtures can
be used, either to supplement natural daylight or to
add light during
the night. Aim for 16 to 18 hours of
light per day, with lamps a foot or so away from the plants. This
is
enough space to allow the heat from
incandescent bulbs to not burn the leaves, yet to provide sufficient
light. If using energy-saving bulbs that
emit much less heat, lamps can be
placed closer. Inexpensive timers from
garden and hardware stores are used to
control such
supplemental lighting.
Keep tender perennial plants, as
well as houseplants (many of which can be considered
tender
perennials), away from drafts. These
could be from doors or windows. If a
sunny day in winter and you open the window for a short time for some
fresh
air, make sure to remember and shut it.
Even a brief exposure to cold once the temperature drops is enough to
injure many tender plants, and is more common than you might expect.
Just as with houseplants, check
tender perennials indoors regularly (at least weekly, or when
watering), for
pests. Many of these are small, so you
may need a magnifier such as for coins, or reading glasses.
Especially
check under leaves, the growing
tips, and the leaf axils where leaves join the stems. If you find
pests, deal with them then before
they spread to other plants and get out of control. You may find
that
some plants are just too
much trouble, being a favorite of pests.
I've found this the case with lantana and whiteflies, for instance.
Much more on the correct conditions
for particular plants, troubleshooting problems then dealing with them,
can be
found in the excellent reference from Storey Publishing by Alice and
Brian
McGowan, Bulbs in the Basement Geraniums on the Windowsill.
Return to
Perry's Perennial
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