Owens Corning

National Gardening Association Making More: Half-Ripe Cuttings

by Karen Jescavage-Bernard

Creating plants from half-ripe (late summer) cuttings makes more than just good financial sense. There are the advantages of speed and ease as well. Many seed-grown perennials require two to three years to produce attractive flowers, and shrubs can take even longer. Using vegetative propagation, by taking cuttings, you can produce mature, flowering plants in a much shorter time. And I find caring for the developing cuttings a much easier task than monitoring the tricky germination, growth and transplanting needs of many seed-propagated plants. Plus, the technique of taking half- ripe cuttings enables the gardener to propagate particularly desirable cultivars that are unobtainable by other methods. Plants that don't come true from seed or those that won't tolerate division, for example, can be multiplied to produce exact duplicates of the parent. It's an excellent method for preserving such attractive ornamental characteristics as leaf variegation.

The best plants to use for half-ripe cuttings are those that develop woody stems during a single season's growth and have finished flowering by late July. Herbaceous perennials such as Dianthus, Helianthemum and Iberis; herbs such as sage, rosemary, lavender, winter savory, santolina and germander; and shrubs like rhododendron, boxwood and juniper all make good candidates. By late summer their stems have reached the midpoint of the current year's growth, halfway between the tender growth of early summer (when "green" or softwood cuttings can be taken) and the hard, woody growth of late fall (when "ripe" or hardwood cuttings are made).

Selecting and making the cut. Half-ripe cuttings are best taken in late summer, when the growth of the current year's stems still show green, pliable tips. Test a stem by bending it: a proper half-ripe candidate should bend almost in half before breaking. The plant must not be producing buds, flowers or fruits when cuttings are taken or else its food reserves won't be channeled into producing new roots.

Take the cuttings early in the morning, before heat, sun or wind cause moisture loss. Each six-inch cutting should have two to three pairs of leaves, plus a growing tip. Use a sharp knife or secateurs to avoid crushing or tearing injury to either the cutting or the parent plant. Place the cuttings in a plastic bag to protect them from dehydration.

Preparing the cuttings. Don't remove the cuttings from the plastic bag until the pots and all other materials have been assembled. Once you're ready, cleanly slice the stem of each cutting with a sharp knife or single-edged razor blade (not secateurs) 1/2 inch below the point where the lowest leaf joins the stem. (This joint is called a "node" and the cut is called an "internodal cut.") Remove any other leaves on the bottom two inches of the cutting. If the leaves are large, cut off the top half of all other leaves, too. This should give you a finished cutting that's two to four inches long with two pairs of leaves plus the growing tip. Rooting hormone is not usually necessary unless only a few cuttings are taken and 100% rooting is important.

Potting up. You'll need several four- to six-inch pots filled with moistened vermiculite or a 50% mixture of damp sand and peat moss. ("Damp" is only as damp as a squeezed tea bag, not wet.) Plan on four cuttings per pot. It's better to use several small pots rather than one large one, so that you can better control the humidity and soil moisture. Clay or plastic? It's your choice. Clay pots promote better and faster root development, but require more time and attention to watering: even brief exposure to dry soil can kill the cuttings. Plastic pots are a better option for the gardener with limited time, but there's the likelihood that you'll overwater.

Position the cuttings around the edge of the pot, where excess moisture will be less of a problem than in the center. Give each cutting two inches of room on all sides and push them, cut end down, an inch deep into the potting mix. Firm the mix around the cuttings, then cover the pot with a clean plastic bag (used bread or food wrappers can lead to mold, yeast or fungus problems). Secure the plastic "tent" to the pot with a rubber band, making certain no plastic touches the cuttings. Use wooden chopsticks or stainless steel table knives to prop up the cover as necessary. (Aluminum utensils should never be placed in the rooting medium.) Place the pot in a warm (60o to 72oF), light spot that's not exposed to direct sun, wind or extreme temperature changes.

Care and control. Careful tending is crucial as the cuttings take hold. Assuming that the right cuttings have been chosen at the right time in their life cycle, the rate at which roots develop depends mostly on the ambient temperature. For most temperate zone species, that's a steady 70oF. Humidity must be carefully monitored. Check the pots at least every other day. If moisture condenses on the inside of the "tent," carefully remove the plastic bag without shaking water on the cuttings, turn it inside out and resecure the rubber band. If condensation continues to be a problem, remove the rubber band from the pot. Above all, resist the temptation to water! The mix should feel barely damp, never wet.

Most cuttings will begin rooting in four to six weeks, but some species may take as long as several months. Cuttings taken from vigorous current growth root more quickly than those taken from old stems or plants. To test for rooting, tug gently on the cutting. Slight resistance indicates that roots have formed. At this point, cut open the top of the plastic tent so that the new plants can adjust to a drier environment. If the cuttings show any sign of wilting, refasten the tent (you can clip the top back together with straight pins or paperclips) for another week, then try again. Once the cuttings are completely acclimated (it takes about a week), they can be transplanted to individual three- to four-inch pots.

Planting out. Don't jump the gun -- your new plants aren't ready for the garden just yet. Let them spend the rest of the early autumn in a protected spot, preferably a cold frame covered by 50% shade cloth or a spunbonded row cover like Reemay. My own "cold frame" is the ground under the filtered shade of an apple tree, which is about as minimal as propagating equipment can get. As long as the soil temperature stays above 43oF, the roots will keep growing. Once frost threatens, close up the top of the cold frame for the winter. I sink my own pots in a leaf-lined pit that I use to force bulbs and mulch them heavily with more leaves. Come spring, your new plants should be ready for planting out.

Heel Cuttings

Heel cuttings are a special type of stem cuttings taken from plants that are slow to develop roots (such as shrub roses) or from old stems (such as the woody stems of rosemary or lavender). Although heel cuttings can be made from softwood, half-ripe or hardwood stems, they are most frequently made from half-ripe material, which is less likely than softwood to succumb to fungal diseases or rots yet gets more of a jump on root formation than fall-taken hardwood cuttings.

Heel cuttings are made from side shoots that are stripped from the main stem, retaining a thin sliver of bark and wood from the parent at the base of the shoot. This sliver is the "heel," and it has two functions: to expose a larger area of root-producing tissue than the conventional straight cut across the base of a cutting, and to provide a firmer base for the cutting to stand on.

To take a heel cutting, select a well-developed side shoot three to six inches long that has two or three pairs of leaves. Place one thumb firmly against the point where the side shoot joins the parent stem. Then, with the shoot held between the thumb and forefinger of the other hand, yank the shoot down quickly. It should separate from the parent with a long "tail." If the shoot does not pull off easily and no other side shoots look suitable, use a sharp knife to cut away the shoot plus a section of the parent stem to make the heel. Trim the tail so that 1/2 inch of old wood from the parent stem still remains. Cleanly pare away rough edges and remove any leaves within two inches of the base. Dip the heel in rooting hormone powder, then proceed as with conventional half-ripe cuttings.

Copyright NGA

Reprinted with permission HouseNet, Inc.

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