University of Vermont Extension
Department of Plant and Soil Science
Fall
News
Article
TO REPOT HOUSEPLANTS, OR NOT
Dr. Leonard Perry, Extension Professor
University of Vermont
This time of year when I am
bringing my houseplants back inside, or even just getting those inside
ready
for winter, I like to repot my houseplants if needed. By
repotting on a warm fall day you can work
outside without risk of injuring these tender plants with cold. I
like potting outside as my messes are much
easier to clean up!
Fall is a good time in the north,
as with leaves off the trees outside in winter and often snow on the
ground, houseplants
often get more light than in summer.
Coupled with warm temperatures indoors from heating, they often grow
well then. If you don’t have much light
indoors though, either artificial or from windows, and your plants
generally
grow little during fall and winter, you may want to wait until spring
to repot.
So how do you know if a plant
needs repotting? Do any of your
houseplants wilt between normal waterings? Do the roots protrude from
drainage
holes? Has there been little or no new growth? Are there white salts on
the
soil surface? If you answered "yes" to any of these questions, it's
probably time to repot. Generally speaking, young and fast growing
plants will
need repotting every six months to a year, older ones every few years.
You can tell when a plant needs
repotting by knocking the soil ball out of the pot and checking the
roots. To do this, invert the plant, hold your hand over the soil and
gently tap the pot edge on the table to loosen the soil. If the roots
are
exposed with little soil covering them, it's time
to repot.
If your plant isn’t growing or
looking well, this is the time to check root color. They should
be firm and often white, with
many tiny root hairs covering them. If
brown, or with discolored patches, and mushy, they likely have a root
rot—often
from overwatering. If just a few sickly
roots, simply prune them off. If most
look sickly, then discard the plant but try making some stem or leaf
cuttings
first.
For repotting, you will need good
quality potting soil, available at garden stores or you can make your
own. If buying one, make sure to get one for
indoor or potted plants. Garden soil, or
mixes containing it, should be avoided as they are not suited for pot
culture
and often keep plants too wet. I often
use a “peat-lite” medium as I used for potting outdoor
plants which contains
peat moss, and some perlite (the small white granules) and perhaps
vermiculite
(the silvery granules, an expanded mica).
A purchased mix also has some nutrition usually, and lime to raise the
soil acidity or pH. If making your own,
you’ll need to at least correct for the latter.
When repotting, use a pot
slightly larger than the one the plant is in currently. Keep the
old potting mix at the same level in
the new pot. If white salts, moss or
other growth is on the surface, scrape this off before planting and
replace
with fresh potting mix. Don't bury the
stem base. Firm the new soil around the old
soil ball, being careful not to pack it down too tightly. Allow at
least
one-half inch space from soil to rim to make watering easier and more
thorough.
Don't forget to fertilize,
following instructions on the label. Water well, but don't overwater
and don’t let the pot sit in a saucer of water. Obviously
you’ll want
to use a saucer if on
furniture, just empty it after watering.
Keep the plant in a warm place at least to start so roots can resume
growth, but don’t place directly on a radiator or wood
stove. Keep
away from
drafts, as these keep pot and soil cool in cold days and nights.
If a plant is too large to repot,
“topdress” it every few years. To topdress, scoop out the
top two or
three inches of soil, taking care not to disturb too many of the
roots. Refill the pot to its original soil level using a fresh potting
mixture.
If your plant is too big already,
especially to put in an even larger pot, you may need to divide off a
piece, or
divide it into sections, if there are obvious shoots or clumps of them
that can
be easily separated such as with the peace lilies. Many, whether
vines like the pothos or an
upright cane like the dumbcane or umbrella plant, may drop leaves as
they get
older. If your plants get leggy, you may
just need to root a section of stem and then pot this, discarding the
original
plant after your cutting is rooted. Those
with woody stems such as the Benjamin fig may be very difficult to
root.
To root a stem section about 3 to
4 inches or so, simply remove the lower leaves, only leaving a few near
the
tip. Some such as the pothos or coleus root
easily in water, others you may want to stick in a rooting medium which
drains
well and has lots of air space. Good
rooting media are perlite, vermiculite, and a 50:50 combination of
these two,
or even moist sand and peat moss mixed.
Place cuttings in pots, then enclose loosely in a plastic bag out of
direct sun. Check daily for moisture,
misting if needed, but don’t keep too wet.
After several weeks, gently tug or pull on the cutting, and if it
doesn’t pull out, it is likely rooted enough to pot.
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Perry's Perennial
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