Extension News

Ask the ISU Extension Garden Experts: Rubber Trees, Begonias and Arbor Vitae

Note to media editors: Got gardening questions? Call the Hortline at (515) 294-3108, Monday-Friday from 10 a.m. to noon and 1 to 4:30 p.m., or e-mail us at hortline@iastate.edu. For more gardening information, visit us at Yard and Garden Online, http://www.yardandgarden.extension.iastate.edu


How can I propagate a rubber tree?

The common rubber tree (Ficus elastica) can be propagated 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.

Materials that are needed to air layer a rubber tree include a sharp knife, sphagnum moss, sheets of clear plastic, twist ties, and a rooting hormone. The procedure for air layering a rubber tree, weeping fig, and other woody Ficus species is as follows.

Select a point on a stem about one to 1.5 feet from a shoot tip. Remove any leaves in the immediate area. Using a sharp knife, make a cut completely around the stem. The cut should penetrate 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. Remove the ring of bark. Scrape the exposed surface to ensure complete removal of soft (cambial) tissue. Dust a small amount of rooting hormone on the exposed surface. (The rooting hormone promotes rapid root development. However, the stem will root without it. It will simply take longer.) Place one or two handfuls of moist sphagnum moss around the exposed area. Wrap a piece of clear plastic around the sphagnum moss. Make sure none of the moss protrudes out the ends of the plastic wrap. Secure the plastic wrap above and below the sphagnum moss with twist ties.

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 bottom twist tie. Remove the twist ties and plastic sheet and pot the rooted stem in a well-drained potting soil.

I have a beautiful rex begonia. Would it be helpful to mist the plant during the winter months?

While rex begonias and many other houseplants prefer high relative humidities, misting is ineffective unless you’re prepared to mist the plants several times a day. Also, rex begonias are generally not fond of water on their foliage.

The relative humidity around houseplants can be increased by using a room humidifier, grouping plants together or placing them on trays (saucers) filled with pebbles and water. When using humidity trays, make sure the pots remain above the water line.

The inner growth in my arborvitae is turning brown. Is this a problem?

The browning of the inner foliage is probably due to seasonal needle drop. It’s normal for evergreens (pine, spruce, fir, juniper, arborvitae, etc.) to shed their oldest (innermost) needles in fall. The innermost needles gradually turn yellow or brown and drop to the ground. Environmental stresses, such as drought, can cause greater than normal loss of needles. The newest (outermost) needles remain green and healthy.


Contacts :

Richard Jauron, Horticulture, (515) 294-1871, rjauron@iastate.edu

Del Marks, Extension Communications and External Relations, (515) 294-9807, delmarks@iastate.edu