Marin IJ Articles

Propagation

by Diane Lynch

One of the nicest things about being a gardener is sharing plants with friends, neighbors and other gardeners. For example, Marin is scattered with a wonderful grape-scented iris brought from Michigan decades ago because one lady has shared it with dozens of people who have passed it on, and on. Gathering seed, dividing perennials, and propagating cuttings are among the options for disseminating plants.

Propagation is one of the most fascinating and mysterious facets of gardening. It is the process of creating new plants of a given species to perpetuate the species. The two basic ways to propagate plants are sexual, which is how seeds come into existence, and asexual, which uses the vegetative or non-floral parts of the plant, such as leaves, stems and roots, to generate a new plant. The most basic form of propagation is plants that self-sow but with a bit of effort and little expense you can propagate enough plants to have an overflowing garden and much to share.

Q: So, can you take just any plant and root a cutting?
A: Different plants lend themselves to various techniques, but some, such as scented geraniums, are so easy to root that you can put a piece in water or directly into the ground and it will root. Plants can be started from cuttings because the tissue contains growth-regulating hormones that are stimulated to turn into root cells. Rooting hormone is also available at nurseries and will improve your chances of success with many plants.

General guidelines for successful cutting propagation include using a healthy plant and watering thoroughly the day before so the plant is well hydrated. Use a light potting soil containing peat moss and vermiculite (you can make your own using equal parts builders sand, peat moss and vermiculite) and keep the cutting damp but not soaked until rooted. A cloudy day is ideal for propagating and a well lit but not too sunny area is best for storing the rooting cuttings. Remove all flowers from cuttings and dont despair if they wilt or the bottom leaves wither. Lateral or side shoots tend to root better than end or terminal shoots. Late summer is a great time to root cuttings so they can be planted during the fall to benefit from our winter rains.

Q: Okay, so what are the techniques?
A: Herbaceous and/or softwood cuttings are taken from perennials, annuals and some trees and shrubs. You can root up to 6 cuttings in a clean 6-inch pot and after they are rooted, transfer them to larger pots or directly into the garden. Softwood refers to green stems that have not hardened or become woodythey will frequently snap off cleanly when at the correct stage. Plants such as rose, Abelia, barberry, cherry, Fuchsia, Clematis, Hibiscus, maple, privet, Hydrangea, Viburnum, Spirea, Weigela and Ginkgo are good candidates. Herbaceous plants that root well using this technique include Aster, Artemisia, lavender, mint, salvia, Penstemon, scented geranium, Pelargonium, thyme, Begonia, Coleus, Gaillardia, Veronica, Impatiens, Monarda, Delphinium and Campanula. Using a sharp clean knife or pruners, take several cuttings (about 1/4" below a leaf) from 2" to 6" in length and gently remove all but the top 2 or 3 leaves and any flowers. Dip in rooting hormone (put a small amount in a saucer so you dont contaminate the whole container) making sure it touches the nodes or where the leaves were removed; tap off excess as too much can inhibit rooting. Use a pencil to make a hole in the damp soil and insert the cutting, making sure the nodes are covered, and gently press the soil around the cutting. Keep consistently damp for the next 4 to 6 weeks. A plastic bag can be used to make a mini greenhouse to keep the humidity suitably high: secure with a rubber band around the top of the pot leaving the drainage holes open. Make sure the plastic doesnt touch the leaves by propping up with sticks or wire if necessary. Its a good idea to open the plastic for an hour or so every day or two to discourage fungal growth. Most plants will not require this plastic bag treatment. You can tell when it is rooted if you gently tug on the cutting and feel resistance.

Layering is a propagation method which occurs naturally in some plants (blackberries, currants, vines) and can be induced in others. A pliant branch is gently staked to the ground and covered with a little loosened, amended soil, leaving the last 6" to 12" above ground and staked straight up. Remove leaves from the area to be underground and gently wound this area by twisting or slightly nicking. Dust on a little rooting hormone and keep the area well watered. This method has the advantage of allowing rooting while still attached to the mother plant. Several weeks later when rooted, the plant can be cut off below the new roots and planted on its own. Rhododendron, honeysuckle, Wisteria, grape, pothos, heart-leaf Philodendron and Clematis lend themselves to this method.

Leaf cuttings work well on some indoor plants such as African violets, Sansevieria and jade plant. African violets can be propagated using the entire leaf or the leaf blade. Dust with a little rooting hormone and insert cutting vertically into the potting soil. Keep damp as described in softwood cuttings above. A tiny new plant will appear in a few weeks at which time the old leaf can be cut off.

There are several other techniques for propagating plants which appear in many basic gardening books. Smith & Hawkens Book of Outdoor Gardening has a good section on propagation. There is something almost magical about growing new plants from cuttings and many gardeners are happy to share starts with others. Experiment with things in your garden and you may be amazed at what you can propagate. Ask neighbors and friends if you can take slips to try rooting some plants you dont have; you can return the favor with a new plant.

Tip of the week:
Scented geraniums are great beginning plants to take cuttings from as they root very easily. At this time of year they should be at the perfect softwood stage for quick rooting.

This article appeared in the Marin Independent Journal on September 2, 2000.