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Repotting Houseplants: Revisited
by John Harmon
November 12, 1999

In a week and a day it will be the winter solstice, the shortest day of the year and probably the hardest time of the winter for your houseplants. I've had a number of requests for information about what to do with dormant houseplants to help them along after a long dark northern winter. One of the things you can do to get your plants ready for the increase in light levels after the solstice is to re-pot them. Here's some tips to help you out.

Before you repot your houseplants check the variety to be sure it's not a plant that likes being pot-bound. Some houseplants will not flower if they're in too big a pot. They will spend all their energy growing new leaves and expanding their root system. One plant that comes to mind is the Ornamental Pepper. One of my books recommends a pot no larger than five inches for this plant. I'm not sure this is a hard and fast rule but the plant will not flower or produce fruit unless it's pot-bound. Don't repot sick plants. They already have enough problems. Wait till the problem has been overcome and the plant is healthy.

Once you have determined that your plant isn't one that needs to be pot bound choose a soil mix that's right for the type of plant. Most plant stores these days carry a variety of potting mixes for specific types of plants. You can also use a general purpose potting soil as a base and adjust it yourself. I like to use soiless mixes for houseplants because it helps to avoid those annoying fungus gnats and I can control the food mixture to suit each type of plant. Compost and manure as well as soil from outdoors can contain fungus gnat eggs or other pests unless it's been sterilized properly. I've purchased both that claimed they were sterile and then had to fight an infestation of some kind.

I mix up three parts of Canadian Sphagnum Peat Moss with one part of perlite as a base mix. For cacti and some succulents I use up to a 50-50 mix of peat and sharp sand. For plants that require a fast draining mix I add more perlite. If you use plastic pots they will tend to hold moisture longer than clay pots. Clay pots are a good choice for cacti or other plants that require drying out between watering. You will find ready made mixes formulated for Orchids, African violets, Succulents and Cacti as well as special tropical mixes. Buy or mix the one that best suits the plants you are re-potting. If you can't find the right mix don't worry too much. Any good commercial soil mix will work for most plants.

Choose a pot that's at least two sizes bigger than the one it was in. Turn the pot upside down while supporting the plant with your fingers and tap the rim of the pot on any hard surface to loosen the root ball. Some potted plants like Lilies will benefit from trimming off a third to half of the root ball before re-potting. Check the variety first. Inspect the root-ball for pests or signs of rotting material. Pick out the old stones or pieces of crockery. Shake as much of the old soil away as possible and remove any damaged roots.

Make sure your new pot is clean. I wash mine with a solution made by adding two tablespoons of ordinary household bleach to a gallon of water. Rinse well with clear water. Line the bottom of the pot with stones or broken pieces of crockery to provide drainage. Add enough fresh soil mix to support the root-ball and lower the plant into it's new pot. Pack new soil gently around the root ball and fill to within a half inch of the rim. Water the plant in with tepid water. This will help to work the new soil in around the roots and give them good contact. After the pot has drained the soil will have settled and more can be added to top it up. Water it in a second time and let it drain. If you are using a soiless mix resume fertilizing with your choice of plant food.

If you have very large plants in tubs that are two big to remove you can top dress. Scrape away or dig out as much of the soil from the top of the tub as you can being careful not to break any roots. The more old soil you manage to remove the better. Fill the tub with new soil and water it in. When it's settled top it up with more soil mix and water again. Check the variety of plant to determine the correct depth to bury the stem. Some plants can have their stems buried and will send out new roots from the portion buried. Other plants will not tolerate being buried deeper. If in doubt fill only to the old soil level.

One last thing you can do without re-potting is to place your houseplants in the bathtub and give them a thorough soaking with clear tepid water till it runs freely out the bottom of the pot. This will help to dissolve and remove any fertilizer salts that have built up over the winter. When salts build up in the soil it can lock up essential nutrients and make them unavailable to your plants.

Once your plants are in new fresh soil they will be in a position to take advantage of the increase in daylight hours after December 21st when the earth will start to tilt back towards the sun.

John Harmon owns and operates Tropicals North. Write to John at The Real Dirt, c\o 211 Wood St., Whitehorse, YT., Y1A 2E4 or e-mail tropnorth@polarcom.com. Website: http://www.netshop.yk.ca/tropnor/

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