University of Vermont Extension 
Department of Plant and Soil Science

 Fall News Article

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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