Snip, a new plant
If starting plants from seed is a miracle, then growing them from cuttings and separations must be magic. How else could it be that entire plants can emerge from stems, leaves and roots as magically as rabbits pop out of hats? It must be sleight of hand.
Truth is, vegetative or asexual propagation -- using parts of “mother plants,” rather than seed, to make more plants -- is more amazing and profound than any of Houdini’s feats. It’s all about how cells multiply and their remarkable ability to differentiate.
Horticulturist and garden writer Nellie Neal, who teaches propagation in Jackson, Miss., says, “Each cell has the potential. A leaf doesn’t look like it could possibly grow a root or a whole new plant, but it can. It’s real-life magic.”
For plants, it’s a matter of survival. In nature, pollination, viable seed, dispersal and successful germination are not guaranteed, so the capacity to regenerate from disparate parts is simply good insurance.
Humans, of course, have capitalized on nature’s prudence. “For us, vegetative propagation is about control,” Neal says. “It’s a way to get more of what you already have, odd plants you can’t buy or that special one in your mama’s garden.”
At the two-acre Cal State Northridge Botanic Garden, garden manager Brian Houck coaches students and volunteers. “We propagate and distribute noteworthy plants in the collection. In fall, we save cuttings of certain annuals, along with cherished tropicals that might freeze outside, and keep them in the greenhouses until the next spring.”
Dylan Hannon, plant propagator at Rancho Santa Ana Botanic Garden in Claremont, cites the values of vegetative propagation in the conservation of endangered plants. “In many cases, cutting-grown plants are better than seed-propagated ones, more genetically fit and better adapted to cultivation.”
In general, cuttings can be made from stems, leaves and assorted underground structures, including roots, rhizomes and tubers. “The principle is: Change the environment of any of these, and embryonic cells in the cambium layer can re-create all three parts,” Houck says. “If only humans could do that.”
Certain plants form offshoots at or near ground level or have tiny plantlets on stems, atop leaves or along leaf margins -- each of which can be removed and grown on their own. Instant gratification.
Tools and techniques for vegetative propagation have changed little since human beings started monkeying around in the garden. The fundamentals are the same: sharp, clean cutters; a sterile rooting medium; adequate heat and humidity; and a modicum of patience.
One huge innovation of the 1960s, tissue culture or in-vitro propagation, revolutionized the nursery industry by allowing cheap mass production of genetically identical plants from specks of matter. You’ve surely seen or even bought one, perhaps a flowering moth orchid at Trader Joe’s for less than $10.
Most gardeners are content and quite successful with traditional practices. Here are some basics from the pros:
“Get everything ready before you start cutting -- pots or flats, whichever you choose, filled with moistened rooting medium,” Neal says. Choices include perlite, pumice, sand or sterilized potting mix.
Hannon roots most cuttings in perlite, a natural inorganic material derived from volcanic rock, and sees problems with potting mix. “Microorganisms can have a ball in there. Fungus spores have a hard time growing in perlite.”
He prefers light-duty, narrow-bladed clippers and sterilizes the blades between each type of plant to avert disease. A five-minute dip in a 1-9 solution of bleach to water is ideal; rubbing alcohol and Lysol are good alternatives. (If bleach is used, be sure to rinse tools thoroughly when finished to prevent corrosion.)
A perfect stem cutting, Neal says, is 4 to 6 inches long, with leaves removed from the bottom half. If remaining leaves are fleshy or wimpy, cut each one in half (as opposed to removing half the leaves) to reduce water loss. “Cut the bottom at an angle so you’ll know which way is up and to create a larger surface for roots to start from.”
Opinions vary on the safety of rooting powders and liquids that combine synthetic plant hormones with fungicide. If you use them, wear vinyl gloves and follow directions carefully. To prevent rot on very fleshy leaf cuttings, Houck coats wounds with powdered sulfur, an ancient fungicide.
Most cuttings get “stuck in” right away. Exceptions include succulents and very woody stem cuttings, which must develop callus tissue before they will root. A week or two in a dry place usually does the trick.
Avoid parts with flowers, or pinch them off, if present. Softwood stem cuttings are taken in spring, semi-hard shoots in late summer and hardwood cuttings in fall and winter. Flowering perennials are propagated in the opposite season of their bloom.
“Succulents are most forgiving,” Hannon says, “though spring is good for most of them. Ultimately, it’s about reading your plants and experimenting. Taking cuttings is like cooking. You get good at it with a lot of practice.
“If you start with good plant material, you’re ahead of the game, but environment is equally important. Protect new cuttings from sun and wind, keep them humid enough and strive for even conditions.”
Offshoots and tiny plantlets are carefully excised with or without roots, depending on the subject, and replanted immediately.
For the humidity and added warmth that cuttings and separations need, plastic bags and terrariums are excellent replacements for yesterday’s cloches and bell jars. “Just be sure to vent them every day,” Neal says.
“In a flat or pot full of cuttings, some will die,” she adds. “Pull those out. After several weeks, give remaining ones a tug. If they resist, the rooting process has started, and soon you’ll have more plants just like their mothers.”
Knowing how simple the process can be, she is wary of friends who practice vegetative propagation. “Yep, I pat ‘em down for clippers before they enter the garden.”
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Cut to the chase
For more information:
“The Nursery-Manual: A Complete Guide to the Multiplication of Plants” (Macmillan), L.H. Bailey’s 1896 classic.
“Making More Plants: The Science, Art, and Joy of Propagation” (Clarkson Potter), a glossy modern tome by Ken Druse.
“Creative Propagation: A Grower’s Guide” (Timber Press), by Peter Thompson.
