Propagation of outdoor and indoor plants by means other than seeds is one of the more interesting facets of gardening. Almost everyone tries it now and then, if only as haphazardly as casually inserting a cut stem into moist soil and hoping that it somehow will make roots and grow into a new plant.
And surprisingly, with nature cooperating, this simple gesture will in fact often produce new plants. But the home gardener who wants to increase his supply of plants can utilize more dependable methods that assure a higher ratio of success. Try them on a few favorite subjects and you`ll find the experience a rewarding one.
Layering is perhaps the most reliable propagagtion technique for the amateur. Most woody plants with long, flexible canes or shoots, such as forsythia, cotoneaster, viburnums, clematis and climbing roses, are easily reproduced by this method.
To start new plants this way, gently bend the shoots or canes into a U about 8 to 10 inches from the tip, make a slight open wound with a sharp knife on the bent portion, then insert the bent portion into a hole about 2 inches deep. Fill the hole with a porous soil containing a generous amount of peat moss and mound the mixture to about an inch or two above the ground level.
The buried portion of the stem must remain undisturbed. To make sure it does, anchor it with a clothespin or coat hanger wire, and weigh down either side of the cane or shoot with bricks or stones. Keep the buried portion moist at all times.
With most plants, the buried stem portion, which will derive nourishment from the parent plant, will develop its own roots by fall. Others may take until spring. Once rooted the new plant can be severed from the parent plant and moved to any desired location.
With clematis vines or climbing roses, one long, pliable shoot can be used to start several new plants at the same time by burying portions of the stem a foot or more apart. This can be useful if you want to extend the planting along a fence or wall.
To propagate house plants take soft, green-stemmed cuttings of them now. These will become larger plants and will make a more showy appearance indoors than if you wait until September, when the growing cycle has slowed.
Cuttings can be taken from such plants as coleus, wax begonias, geraniums, impatiens, and foliage and vining house plants that have been placed outdoors for the summer. Snip off the tip of soft, green growth about 5 inches in length, remove the lower leaves, and make a clean cut with a razor just below the bottom node (leaf joint).
Dip the cut ends in a rooting hormone, which you can get at any garden store, and place the cuttings in pots or flats of soil, inserting them so that two nodes of the stem are covered. Keep the cuttings moist and out of direct sunlight.
After two or three weeks, tugging slightly on a cutting will determine whether roots have started to develop. If they offer good resistance, the cuttings can be removed and potted up separately for new plants.
Q--I received a well-rooted division of a Kafir lily from a friend. How should I handle it to get a healthy, new plant?
A--Divisions of Kafir lilies (Clivia) should be potted in a rich soil mixed with some sand. Use a 6-inch or larger pot because these plants develop substantial heavy roots. Grow in a cool spot where there is filtered sunlight. Soil should be kept evenly moist. A division may have to be grown for several years before it will produce flowers.
Q--Will seeds from weeds tossed on our compost pile sprout when the compost is used later in the garden?
A--Usually the heat generated in the composting action will destroy most seeds, but there always is the possibility that some will remain viable. It is a good rule, therefore, not to put weeds that have gone to seed on the pile.
Q--When is the proper time to divide Oriental poppies?
A--Divide the plants in August after the foliage has withered and plants become dormant. New foliage will appear in late autumn.
Q--What care does Swedish ivy in a hanging basket require to keep it attractive? Leaves on my plant often turn yellow.
A--Swedish ivy (Plectrantus australis) needs a cool location with indirect or filtered light. Too much heat and sun will turn foliage yellow. Water as necessary to keep soil on the moist side.
Send questions about gardening to Art Kozelka in care of Know-how, The Chicago Tribune, 435 N. Michigan Ave., Chicago, Ill. 60611.