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Home > Begonian > Volume 68 (March/April 2001, page 62)

Startin' Out
by Jim Hannah

Last time, we discussed the vegetative propagation of cane-like and Rex begonias. This leaves several types yet to be covered. Let's look at two more: the shrub and rhizomatous begonias. Both types are among the easiest to propagate.

In a sense, we've already covered the shrub begonias. Just use the method we outlined last issue for the cane-like begonias. It works just as well with the shrubbies. Do remember to take stem segments having at least three and preferably four nodes. Remove any leaves from the lower two segments. Place the cutting in water so that the two lower nodes are covered. Pot up as soon as root formation begins. Be gentle. Don't injure the new root buds or rub them off the stem while potting up the cuttings.

The rhizomatous begonias give you quite a choice of methods. We've already covered one of them last time -- the leaf segment method used with Rex begonias. For this, all you need is a covered propagation box containing about an inch and a half of moistened vermiculite. You can use the Rex method and it works quite well. Each segment should include a main vein right up to the point where it meets the stem. You'll need a bit of patience, too. Some segments can take months to produce the first new leaves.

For the rhizomatous begonias, there's a second leaf method. It's not often used with the Rexes because Rex leaves are usually so large. If your rhizomatous plant has small enough leaves, cut off a leaf so that there's about an inch of stem still attached to it. Use a sharp knife or razor blade to make the cut. I really don't know if a diagonal or straight cut is better. Perhaps you could experiment and share your findings.

Place the leaf stem down in the propagating medium with the leaf part just above the surface. We usually place the leaf at an angle to the medium surface to increase the amount of light that falls on it. This whole leaf technique is exactly the same as that used for African violets.

The choice between using the whole leaf or a leaf segment is a matter of size. If the plant's leaves are small, the whole leaf method is a good choice. If the leaves are so large that they won't easily fit into your propagation box, use the leaf segment method. Use at least three leaves or segments to improve the odds of success. In any event, choose good, healthy leaves. That will improve the odds more than which method you use.

There's yet another way to produce a new rhizomatous plant and that's to use a section of the rhizome. The 'ideal' cutting will include a growing tip and a leaf, but other sections of rhizome can also be used with success. The rhizome is placed on a growing medium (we use a seed starter mix) and barely covered with the same medium. Any leaves are left above the surface. Then, it's into the propagation box with the cutting until growth is well along. Whenever you use a propagation box method, do remember to take humidity into account. The key is to provide a slow change from high to lower humidity for new plantlets when they are removed from the box. The plant adjustment from high to lower humidity will take several weeks.

Next time, I'll chat about growing begonias under fluorescent lights.

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