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Home > Begonian > Volume 68 (January/February 2001, pages 28 - 30)

Startin' Out
by Jim Hannah

Somewhere along the line you'll want to make a new plant from one you already have.  Perhaps the old plant has grown too large and leggy or maybe you want to share a plant you particularly like with a friend. Happily, many types of begonias are easy to propagate by vegetative methods. This is quite different from growing new plants from seed. I'll cover two types, cane-like and Rex begonia, below. But first a little bit of background is worth adding.

Begonias, like most plants, can be grouped in many ways. One is to divide them into species and hybrids. A species begonia is identical to begonias growing in the wild. Plant seeds from species begonias pollinated by the same species and you'll get a carbon copy of the original almost every time. There may be some slight variation from plant to plant -- a very small shift in flower tint, for example -- but it will be minor. Hybrids, on the other hand are plants with more than one species, sometimes many, in their parentage. Plant seeds from hybrids and the resulting plants will not all be the same. In some instances they will be quite different from their parents and each other.

So ... how do you make a carbon copy of a hybrid? You use a piece of the plant itself and coax it into growing roots and forming a new plant. You can use the same methods on species begonias too, of course. Let's start with a method for making new cane-like begonias from existing plants.

The begonias called 'cane-like' are among the very easiest to propagate. All you need is a glass or cup of water, a razor blade, or very sharp knife, and a well-lit spot out of direct sunlight. For lighting, we use a simple fluorescent 'shop light' with 40 watt tubes set a few inches above the cuttings. A bright window works just as well. Just avoid direct sunlight.

Select a growing cane tip which includes 4 or 5 leaf nodes. Cut it off on an angle about a half inch below the 4th or 5th node. Then remove all but the two top leaves. Place the cutting in a glass or cup of water so that the lower leaf-free nodes are under water. If you wish, you can cut another section from the same cane. Again, cut off the lower leaves. The cutting will develop a new growing tip at the point where the top leaf joins the stem.

Can't find a good section with 4 leaf nodes? Don't despair. You can get away with 3 or even I node section cuttings. Just be sure that there's a leaf on the top node and that the lower nodes are under water.

The cuttings should be given at least 12 hours of light a day. Check the cuttings every few days. Add water as needed to keep the lower nodes submerged. The first sign of something happening will be the appearance of little white dots on the underwater portion of the stem. These will become the roots of the new plant.

Pot up the cutting when the roots have grown to about a half inch long. The roots are tender. Be very gentle as you fill the container with soil. Any good potting soil will do. Pot the cutting as deep in the soil as it was in the water. Watering with dilute fertilizer will help offset the shock of transplanting. Finally, treat the new plant just as you did the parent. That's all there is to it.

Rexes are next. These are peculiar rascals with unbelievably mixed-up parentage. We love them. If you like surprises, just grow Rexes from seed. To make a Rex copy all you need is a leaf, a razor blade or very sharp knife, a cheap plastic sprayer for misting and a clear top container at least 4 inches deep containing an inch of damp horticultural vermiculite.

A Rex leaf has several main veins. Starting from the point where the stem joins the leaf, cut the leaf into wedge-shaped sections so that each section contains a main vein running up the center and the smaller veins which lead to it. You'll get three or four cuttings from a good healthy leaf.

Make a slot in the vermiculite for each wedge with a knife blade or spoon handle. Place the wedge in the slot with the point which joined the original stem at the bottom. We position them so that the wedge slants back at a 45 degree angle, but this isn't critical. Gently firm the vermiculite around the wedge to hold it in place. Mist the wedges and put the cover on the container. Provide light as noted above for the cane-like cuttings. We mist the wedges every few days, but I don't know if it's really necessary.

Be patient. Cane cuttings will start to show the characteristic rootlet dots in a week or so. Rex leaf wedges, on the other hand, may take months before they start producing the first few new leaves which signal the development of a new plant. The wedges normally start growing roots in a few weeks, but the leaves can take a long time. When the wedges have grown leaves of a least the size of a dime, they are ready for transplanting.

The plantlets are fragile. Be careful not to break off the roots or leaves. Carefully lift them from the container, remove as much of the vermiculite as possible, and pot up using any good potting soil. Remember that these new plants have been growing in 100% humidity. You'll want to put the pots into clear plastic bags at first and then gradually open and lower the plastic over a couple of weeks. This will allow the plants to adapt to your normal growing conditions.

Incidentally, some hybrids are patented. The originator who develops a hybrid can protect his hard work by patenting the plant. If you are thinking of selling the plants you propagate, be sure they aren't patented. You can get into legal trouble selling vegetatively propagated patented plants.

We'll continue with new plants from old next time.

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