Learn how to take tip and stem cuttings with master gardener Paul James and professor of plant propagation Steve Silk.
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Planting a seed is a great method of plant propagation, but cuttings are a quick, fun and inexpensive way to experiment with the science of plant reproduction. Master gardener Paul James and plant propagator Steve Silk explain how to take tip and stem cuttings in order to produce more plants for the garden.
Colorful, lush, and jam-packed with interesting foliage, this isn't a tropical rainforest or a remote jungle, but this garden is just as exotic largely because there's just so many plants. "The main thing is that I want abundance," says Silk. "I want lots of stuff." Because having a number of plants can get fairly expensive, Silk's solution is a propagation technique known as tip cuttings. It makes sense since a tremendous amount of a plant's growth is concentrated at the tips. So why not prune that off and plant it up to create a whole new plant?
Morning is the best time to take cuttings because that's when the plant is the most vigorous. To take your tip cutting, make a cut above a set of branches so that the plant will still look nice. Take a cutting that has at least three sets of leaves. Submerge the wound area in water to keep the cutting nice and fresh until transplanting. While you're at it, take a few more cuttings.
"This is angel's trumpet," says Silk. "It's got huge leaves, huge flowers and is an incredibly fragrant plant, one of my favorites." According to Silk, it not only looks like a tree, it is a tree grown from a six-inch cutting taken in the fall. "And it'll get a lot taller before the season is out." The same tip cutting rules apply to angel's trumpet. Cut back at just above the leaf node (the point at which the leaf is connected to the stem), and this time make sure to have at least three leaves rather than three sets of leaves. Steer clear of flowers on the cutting because they zap energy from the plant during the rooting process. Flower buds are fine; they'll get pruned away later.
Here is a sweet potato vine, an ornamental version of the typical sweet potato. This particular cultivar 'Margarita' is valued for its lime-green foliage. Silk suggests using a slightly different kind of cutting technique since it doesn't easily root with tip cuttings.
Taking a much bigger piece from the sweet potato vine, Silk utilizes the stem rather than the tip. For plants that don't root easily from tip cuttings, stem cuttings are a great alternative.
"When I'm ready to stick my cuttings, that is put them in the potting soil," says Silk, "I like to get all my materials ready at hand." His propagation supplies consist of:
"Gardeners always hear about moist but well-draining soil and how that's important to gardening," says Silk. "It's particularly important to cuttings." Cuttings don't really need nutrients because they don't have any roots to take up nutrients. However, they do need to stay moist so they won't dry out. Cuttings can't be too wet or they'll rot, so it's best to have moist and well-draining soil.
To create that perfect balance, Silk uses one part peat moss which retains moisture and one part perlite which improves drainage. Then he adds enough water so that when you squeeze a handful of the peat-perlite mix, only a few drops escape.
With the mix ready to go, Silk starts sticking the cuttings. He begins with the coleus because it is so easy to root. "I'll begin trimming the cutting, but I want at least three pairs of leaves." Smaller cuttings can use up the plant's food supply before it roots, so snip them off to redirect the energy. Flowers on cuttings can also take up energy, so snip them as well. Silk cuts off the bottom pair of leaves right at the stem. It's at those two cuts where the roots will form on the cutting.
There is one more recommended step before planting. Though it's not absolutely necessary, particularly for coleus, Silk uses a rooting hormone--a manufactured version of the natural plant growth hormone, auxin. It promotes good root growth and is easy to use. Simply dip the stem of the cutting in the rooting hormone, dust or shake off any excess and dunk the plant into the potting mix. When the cutting is all set in its potting medium, Silk is ready to move it to its environment for rooting. If you're overwintering, label the cuttings. Coleus leaves can change considerably after months under fluorescent lights.
For the angel's trumpet, trim the leaves away from the bottom of the stem and cut away any flower buds. Since leaves transpire a lot of moisture, Silk reduces their size by cutting the larger leaves in half. Less surface area means less moisture loss. Then, dip, dust and dunk.
With the sweet potato vine, Silk is more concerned with the stem than the tip. He makes a second cutting along the base of the stem. The new cutting is a portion of stem and two leaves. All the cuttings go into a plastic sweater box that doubles as a greenhouse. Pour one half-inch of water on the bottom of the container for a moist, humid environment, pop the lid on and store under florescent lights or in indirect sunlight.
After a few days, check the status of your cuttings to see if they have rooted. One sure sign that the plants are rooting is new growth. Roots are a sure sign of success. (Moldy or squishy cuttings clearly didn't work. They probably need less humidity, so next time try an aquarium with a lid for better air circulation.) If you can pick the whole pot up by the plant stem, your cuttings have rooted. At this point they're ready to be hardened off. "These plants are rooted, but they're not ready to go in the garden yet," says Silk. "They need to acclimate to wind, sunlight and that sort of thing, so I'll put them in a protected location outside for maybe three days to a week. Let them rest in that location and get accustomed to being in an outdoor environment." And the most gratifying part of tip cuttings is a lush garden that didn't cost an arm and a leg.
Experiment with taking cuttings of all kinds of plants. Not everything will root, but you'll have fun trying. And remember, there are different methods to getting plants to root. If tip cuttings don't work, try stem cuttings. In fact, Silk overwinters many tip cuttings from hard to find plants. They limp along for months under the fluorescents and are often covered in aphids and spider mites, but come spring, most bounce back to life with just a little TLC.