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Houseplant Propagation
by Angelique Wood, Burnaby GARDENWORKS
March 1, 1997


Early spring is a good time to look at your house plants and assess what housekeeping needs to be done. Does your peace lily (Spathephyllum spp.) look cramped in its pot? Does your dumb cane (Dieffenbachia ameona or D. picta) look straggly and skinny? Is your corn plant (Dracaena fragans) hitting the ceiling? Take care of these problems in the spring, when they are coming out of dormancy and will recover quickly. If you take cuttings, prune, divide or repot your house plants in the spring, they will have all summer and fall to become well established again before they endure their long winter dormancy.


WHEN TO REPOT OR DIVIDE

If you have owned your plants for more than 2 years, it is a good idea to repot them, although some types prefer to become rootbound in their pots. If the roots of the plant are coming through the drain holes of the pot, or if the pot is taken up mostly by roots, it is time to repot.
When repotting a large plant, first decide whether or not you wish the plant to continue growing larger. If it has already reached the proportions that are "right" for its room, all the plant will need is root pruning and re-filling with good indoor potting soil. If you wish the plant to continue to grow larger, repot into a pot that at least 2" (5 cm), but no more than 4" (10 cm) larger than the old pot.


TO ROOT PRUNE

Place the plant on its side and gently pull the pot away from the plant. This may be made easier by placing the plant on an angle, or completely on its side. Inspect the roots, and remove dead roots from the outer edges, as well as up to a quarter of the total root mass. Then remove the top quarter of the soil and replace the plant into the same container. Add fresh indoor potting soil around the sides of the pot, tamping it down slightly with your fingers to get rid of air pockets. Finish by topping the pot up with more fresh soil, and watering gently.
Root pruning is also used by bonsai growers to limit the eventual size of their masterpieces, any by people wanting to grow large trees in containers.


DIVIDING A PLANT

If your plant is getting too large, or if you want to share it with a friend, you can divide any of the types that multiply by forming new plants around the base of the original. These include snake plants (Sanseviera), cast-iron plants (Aspidistra), Chinese evergreens (Aglaonema) African violets (Saintpaulia) and peace lilies (Spathephyllum).
Unpot your plant as outlined above, and look for smaller plants growing around the original. Some people refer to these as mothers and babies. Separate a baby from the mother by pulling first from the top, and then cutting away roots till it is free. The young plant will be very accepting of this change, and will become independent faster if it has a large number of roots. Make sure to provide constant temperatures and bright, but indirect light. Your new division will not need as much water or fertilizer as the mother plant, because it will have a fairly undeveloped root system to begin with.


PRUNING CANES

Cane-forming plants, such as corn plants (Dracaena fragrans massangeana), dragon trees (Dracaena marginata), dumb canes (Dieffenbachia amoena or D. picta) and yuccas (Yucca elephantipes) all grow to hit the ceiling unless you can do something to control their upward growth. You can simply prune them if you want, cutting right across the cane. The plant will re-sprout under the cut, and new leaves will form a new crown of growth.


AIR LAYERING

Air layering allows the new plant to have its growth supported by the parent while it grows roots. It is the best method for multiplying many woody-stemmed plants, including corn plants (Dracaena fragrans massangeana), dragon trees (Dracaena marginata), rubber plants (Ficus elastica) and dumb canes (Dieffenbachia amoena or D. picta).
First, choose a point along the stem 12-24" (30-60 cm) from the top of the plant. This is where the most growth and activity occurs in the plant, so rooting will be strongest. Remove the leaves to allow a 4-6" (10-20cm) gap in which to make your cut.
Using a sharp knife, make a diagonal cut 3/4 of the way across the stem. Gently pry the cut open and prop it open with a toothpick. Dust the top surface with rooting hormone. Next, wrap dampened moss around the wound and toothpick.

The moss will be the rooting medium for the new plant. Wrap the moss in a plastic bag to retain moisture. Seal the top and bottom of the plastic with tape. Check the moss every week to make sure it is still damp, and look for root growth. Once the roots have filled the bag, cut the plantlet from the parent plant. Cut at lest 2 inches below the root bag, and unwrap the bag gently. Plant the new cutting in fresh indoor potting soil, and stake the new plant to hold it upright.
The original plant will sprout new growth under its newly pruned point, and continue growing upwards.
Cane-forming plants are among the most difficult tropicals to root when using normal methods of taking cuttings. Wandering Jews (Tradescantia spp.) English ivy (Hedera helix), Pothos (Epipremnum spp.) and many other tropicals are so easy to root, even in a jar of water, but cane-forming and woody plants are different. Air layering is the most successful method of multiplying these plants, which are finicky any other way. We hope you have good success with it, along with all your other gardening adventures this spring.

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