Pitfalls in Rooting

I’m disappointed by the difficulty I have in rooting cuttings. I keep trying, remembering how we rooted cuttings by the tens of thousands at the nur­ser­ies where I used to work, but the success I had there didn’t follow me home. Every fall I try, but fail, to save cuttings of the scented geraniums that grow too big in the garden to bring indoors. Or I’ll dream up some great scheme for starting a hedge of old roses, or an edging of germander, or just a pair of myrtle topiaries. Sometimes I fall in love with some new shrub at a friend’s garden and try to start my own from a slip. Most of this comes to naught. I’m lucky if one of a dozen cuttings actually forms roots and grows into a healthy new plant.

It’s ironic because our climate is so humid that plants sometimes form roots in the open air. In the garden, I’ve had pineapple sage plants bear a fringe of inch-long roots up and down the stems. Dyer’s knotweed regularly sprouts a tuft of roots at each node. On the windowsill, Christmas cactus, sedums, and other succulents get so hairy with roots that they look as though furry animals have shed on them. It’s easy to root cuttings of those plants, because they already have roots.

The problem I have with most cuttings is maintaining enough humidity so the leaves don’t wilt and wither, but not so much that they rot. I usually stick cuttings in individual small pots filled with a damp mixture of commercial potting soil and coarse perlite. If I leave the pots sitting in the open air (but shaded from direct sun), the cuttings almost always wilt to death within a few days. Sometimes I strip off most of the leaves, hoping to reduce moisture loss, but even so, the few remaining leaves wither.

Enclosing cuttings to surround them with moist air seems like a good way to keep the leaves from drying out, but the question is what covering to use. Making little tents out of plastic produce bags and bamboo stakes never works for me. If the bag touches the cutting, it’s all over: leaves in contact with plastic rot right away. Making big tents out of dry cleaners’ bags-so the plastic is several inches away from the leaves-protects the cutting from immediate rot, but big tents are unwieldy and tip over easily.

I’ve also tried cutting the bottoms out of milk jugs and setting those containers over the potted cuttings, or putting the pots into plastic shoeboxes or glass terrariums. These methods work for other folks, but not for me; sooner or later, my cuttings either wilt or rot. It’s such a fine line between too little and too much moisture. And there’s always the risk of overheating. Even an hour’s exposure to direct sun can be enough to bake enclosed cuttings.

Anxious to keep them out of the sun, I position the cuttings in a bright but shaded spot, but then cool temperatures can be a problem. Cuttings root faster in warmer soil, but where is it warm in the shade? In the summer, I don’t have a good place, unless I use a heat pad or soil-heating cable. In the winter, I could put them atop a radiator that’s in front of a north window. But there’s also a fine line between too little and too much heat. Too cool, and the cuttings have more time to rot before they root. Too warm, and they rot even faster than they root.

I haven’t mentioned rooting hormone. I usually do dip the cut ends in Rootone powder, but I don’t think that makes much difference if they’re going to die for other reasons.

The past few years, I’ve almost given up on trying to root cuttings in potting soil and have been rooting them in jars of water on the windowsill instead. At least they don’t wilt, and many actually root fine. As soon as the roots emerge-when they’re just 1/8 to 1/4 inch long-I pot up the cutting and put it in a tent. Often within a week, those roots elongate into the soil and start functioning well enough that I can remove the tent. This works with some cuttings-tips of mints, monardas, salvias-but not with woody cuttings such as rosemary or bay. (To be honest, I’ve never successfully rooted a woody cutting at home by any method.)

I usually attribute my failures to less-than-perfect conditions. The professional horticultural literature specifies when and how to take cuttings of different plants, how much hormone to apply, how to time the automatic mist system, what soil and air temperatures to maintain-all determined in modern greenhouse experiments. That’s great in theory, but who has such carefully controlled conditions at home?

On the other hand, people have been rooting cuttings for thousands of years without any high-tech gear. In “folk” horticulture, making cuttings is easy. I know people who snatch bits of any interesting plants they see on vacation, stow the cuttings in a purse or suitcase for several days, and stick them in the ground or a pot when they get home. I’m amazed that these cuttings root and thrive, but the folks who make them are oblivious to their success. They simply expect plants to grow, and their faith is rewarded.

Maybe I just don’t have enough faith . . . .

Rita Buchanan of Winsted, Connecticut, is a writer and herb gardener of long experience and a former associate editor of The Herb Companion. She is also a former editor of Fine Gardening magazine.

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