Green for Your Garden—and Your Wallet!
Don’t let the scientific term vegetative propagation scare you—it just means growing new plants from established specimens rather than seed. Learning how to propagate plants is an easy and economical means of increasing your plant stock. “Propagation is a wonderful way to make more of your favorite varieties to fill in blank spots in your yard or keep a few backups of a prized plant in case your original dies,” says horticulturist Marc Hachadourian, who manages the Nolen Greenhouses at The New York Botanical Garden. Many gardeners also enjoy increasing the number of their favorite specimens to share with friends as gifts.
Some of the more advanced techniques, like grafting, take a bit of skill. But there are easier techniques that suit beginners—including rooting stem and leaf cuttings, root division, and ground layering—no greenhouse required. You can propagate most plants on a windowsill that gets only indirect light (harsh sunlight will bake tender cuttings). Follow the advice on the following pages—and be patient. “Sometimes it can take longer than you think to get adequate roots,” says Hachadourian. “Plants won’t be rushed.”
So-called softwood cuttings, such as coleus and pelargonium (common geraniums), are easiest to root. Semihardwood cuttings, like boxwood, take longer, though willows and forsythia are easy to propagate in early spring before they bloom. Timing varies enormously, so always research the right time to take cuttings for each plant.
Take cuttings about 3 inches long using a clean, sharp pruner (dull blades will crush stems and encourage rot). Strip away the lower leaves.
Stem Cuttings: Step 2
Dip the bottom tip of the cutting in a rooting solution (available at garden centers), following the package directions. These hormones signal plants to put out roots. Don’t use too much solution, since overdoing it can actually inhibit rooting. Hachadourian prefers powder over liquid so that he can see how much he has applied.
Stem Cuttings: Step 3
Fill a tray with a dampened, sterile growing medium, such as perlite. Using a pencil, poke holes and insert the prepared cuttings. This technique keeps the solution from rubbing off, as it would if you pushed the twigs in. Gently firm up the medium around the cuttings.
Stem Cuttings: Step 4
Make a cover or dome to create a moist environment, like a miniature greenhouse, to foster the growth of the roots. Seed-starting trays often come with their own covers; some gardeners use the top part of a large plastic soda bottle that has been cut in half. Place the tray in indirect sunlight, and keep moist.
Stem Cuttings: Step 5
After a few weeks, lightly tug on the stem. If the cutting resists, enough roots have formed for it to be removed and planted in a pot or outside.
Note: Many softwood cuttings can also be grown in a glass of water. With a sharp, clean knife, cut a 2- to 3-inch stem with several good leaves, and place it in a glass of water (make sure the leaves stay above the water line). Keep cuttings out of direct sunlight and make sure the water level stays constant. After a week or so, look for a developing root system. When the roots are about 1 inch long, it’s time to take the cutting out and plant it in a soilless potting mix. Don’t wait too long or the cutting will develop “water roots” that can absorb nutrients only from water and won’t grow properly once they are planted in soil.
Many clumping perennials that develop a thick mass of roots—including hosta, daylilies, daisies, astilbe, and Siberian iris—can be divided to make more plants when they are starting to leaf out in spring or before they bloom. Consult a garden encyclopedia to learn when you should divide any particular plant; some species should be dormant, others need to be in active growth.
Using a garden spade, dig up the plant with as big a root ball as you can manage.
Root Division: Step 2
Wash some of the soil off the plant’s roots so that you can accurately judge the natural place to divide the plant—between major stems, for example. In some cases there may be visible plantlets that can be separated.
Root Division: Step 3
If the root ball is soft enough, you can use your hands or a small garden fork to divide the plant. Use a cutting tool, like a garden knife, for tougher jobs, such as dividing asters.
Root Division: Step 4
Don’t divide the plant into too many sections. Every section should have a healthy amount of root mass; those that retain a part of the thick core will recover fastest. Don’t divide too frequently, either. It’s best to go three years or more between dividing most specimens.
This method works easily on mostly tropical and subtropical species, including certain begonias, Cape primrose (Streptocarpus), and leafy succulents.
Take a thick leaf and cut it into 1-inch-wide sections with a clean, sharp razor blade. Each section should include a strong vein.
Leaf Cuttings: Step 2
Place the sections vertically, vein-side down, in a tray of moistened rooting medium, such as perlite; cover with a dome to keep moisture in.
Leaf Cuttings: Step 3
When roots, followed by small leaves, form at the base of the cuttings, they’re ready to be transplanted to a small container with potting mix.
Note: African violet leaves can also be rooted from leaf stems placed in water. Cut off a few young, full-grown leaf stems in late winter to midsummer. Fill a glass jar with water. Cover the top with aluminum foil with several holes punched in it to hold the leaves erect and out of the water; leave one hole for adding water. Keep cuttings out of direct sunlight, and make sure the water level stays constant. Look for a developed root system of 1 inch or so. Don’t let the plant stay in the glass long enough to develop “water roots,” which won’t grow well in soil.
This method is suited to large, woody plants, such as climbing roses, clematis, hydrangea, and other flowering shrubs and vines.
In late spring or early summer, take a 2- to 3-foot stem that is not too old and hard, and clip off any flower buds. Dig a shallow trench. Place the stem a couple of inches down and scatter soil over it. The stem will remain attached to the mother plant for the duration of the process. Use a rock or a landscape-cloth pin to hold it down; press firmly to purposely injure or crack the stem to encourage rooting.
Ground Layering: Step 2
Keep the soil moist or use mulch to keep moisture in. Over a period of weeks, the plant will grow roots all along its leaf nodes (where the leaf joins the stem). From time to time, brush off the soil lightly to check root development.
Ground Layering: Step 3
Once a good set of roots has developed all along the stem, each section can be severed with a clean, sharp blade, then lifted out and transplanted elsewhere to make a new plant that will grow on its own.