Many houseplants don't age gracefully. Some lose their lower leaves and become tall, leggy, and unattractive. Others simply become too big. Instead of tossing the plants, many old houseplants can be renewed by air layering.

Air layering is a procedure used to induce roots to form on a plant stem while it is still attached to the parent plant. Complete or partial girdling of the plant stem interrupts the downward translocation of carbohydrates and other compounds. The accumulation of these compounds promotes rooting at the point of injury.

There are different ways to air layer houseplants depending on the plant species. The vascular tissues of woody dicotyledons (dicots) form a complete cylinder below the bark. In monocotyledons (monocots), the vascular tissues are organized into bundles that are scattered throughout the stem. Different procedures are required to air layer dicots and monocots due to their differences in plant structure.

Woody dicots, such as the weeping fig and rubber tree, can be successfully air layered by following the steps listed below.

1. Air layer a stem 1 to 2 feet from the shoot tip. If necessary, remove 1 or 2 leaves to insure adequate working space.
2. Using a sharp knife, make a cut completely around the stem. The cut should penetrate the bark down to the woody center of the stem. One inch below the first cut, make a second cut completely around the stem. Finally, make a third cut connecting the previous two cuts.
3. Remove the ring of bark. Scrape the exposed surface to insure complete removal of cambial tissue.
4. Dust a small amount of rooting hormone on the exposed surface.
5. Place 1 or 2 handfuls of moist sphagnum moss around the exposed area.
6. Wrap a piece of clear plastic around the sphagnum moss. Make sure none of the moss protrudes out the ends of the plastic wrap.
7. Secure the plastic wrap above and below the sphagnum moss with twist ties.
8. Roots should appear in the sphagnum moss in a few weeks. When a good root system has developed, cut off the stem just below the roots. Remove the twist ties and plastic and pot the rooted stem into a well-drained potting mix.

The procedure for air layering monocots, such as the dumbcane or Dieffenbachia, is similar to that for woody dicots. The second step, however, is different.

1. Select a point about 1 to 2 feet from the shoot tip.
2. Make a sloping cut down toward the center of the stem. Immediately below the first cut, make an upward cut. The second cut should be approximately 1/2 to 1 inch below the first. The two cuts should meet in the center of the stem. Remove the cut portion of the stem.
3. Dust a small amount of the rooting hormone on the exposed area.
4. The remaining air layering steps are the same as for the woody dicots.

Once potted, keep the new plant well watered and in bright, indirect light. The plant should be well established within a few weeks and it can be moved to its preferred location indoors. The parent plant can be discarded if no additional plants are desired.

This article originally appeared in the January 15, 1999 issue, p. 3.