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Repotting Houseplants
by John Harmon
March 7, 1999

The month of March is upon us and the daylight hours are building rapidly. In Whitehorse we are up over ten hours now. If you have a heated greenhouse you will have enough hours of daylight by the end of the month to fire up and get going. For your houseplants March means spring and there's enough light for them to start growing again. Here's some things you can do to help them along.

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.

Remember to ease them back into direct sunlight. After a winter of low light too much direct sun may burn the leaves. Your houseplants will quickly send out new roots looking for nutrients and will be ready to take advantage of all this extra light and start growing again after the long winter of low light levels. 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 this is the end

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