Propagating Your Garden

By Kelly Orzel
Published on November 24, 2017
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Add rosemary to your garden.
Add rosemary to your garden.
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“The Backyard Gardener” by Kelly Orzel will help you become a better gardener.
“The Backyard Gardener” by Kelly Orzel will help you become a better gardener.

Cuttings are underrated as a propagation method. It’s as natural as breathing for some plants to root–they’ll do it without any help from you. Have you ever put mint or basil in a glass of water only to see white hair roots develop within a week? Other plants need a bit more inducement to root. The primary motivation for taking cuttings over seeding is to preserve the exact characteristics of a plant that does not comes true to seed. Or, if germination is particularly spotty, it’s often easier to take cuttings as a little extra insurance so you don’t lose any of your favorite performers. Sometimes this practice is referred to as vegetative, or asexual, propagation because there is no seed making involved in creating offspring. Cuttings are like cloning — you’re using one piece of a living organism to make an identical replica. For herbs like French tarragon and lavender, this is the only way to get true plants, but for others like bay leaf it is a shortcut. Bay takes three to twelve months to germinate and another two to three years growing in a pot before it can be planted out, but a cutting will root in three to six months … it’s really a no-brainer which method to use.

For the best chance of success, always choose shoots from thriving, healthy plants with fresh growth and use clean, sharp snips or knife. You can take root, leaf, or stem cuttings, but the most common is stem. Then there are softwood, semi-ripe, and hardwood type cuttings, but this refers more to when the shoot is being cut rather than the part of the plant being used. Softwood cuttings are taken from new growth in spring through early summer and are the easiest to root. They are your “most likely to succeed” type of cutting, but you have to be aware not to let them dry out. When taking cuttings, I carry a large zip lock bag that I periodically mist and keep closed to keep the cuttings moist. Semi-ripe stems look as if their growth has begun to slow–the stem is becoming more woody. Cut this in late summer, keeping in mind that these will take longer to root than fresh softwood cuttings. Hardwood cuttings taken in late autumn through winter off deciduous trees and shrubs should root by the following spring.

Softwood and semi-ripe cuttings are taken the same way, cut four- to-six-inch lengths with four to six sets of leaves at an angle from the stem tip, carefully removing the lower two-thirds leaves so as not to exhaust your new roots. If you tear or squish the stem, it may make rooting difficult and invite disease. Then make a new cut just below a bare node near the bottom. Shaving a sliver from the side of the bark of semi-ripe cuttings can stimulate the rooting cells when the wound calluses over. Dip the bottom and barren nodes of the cutting into rooting hormone to promote root development.

Just be sure to pour the powder you’re using into a separate dish and discard afterward to avoid contamination with your supply. Use a soil mix similar to what you used for seed starting–garden soil is too heavy. Also, mixing a few teaspoons of seaweed meal and bonemeal into the soil will get your cutting off to a good start without generating too much top growth from nitrogen fertilizers. Gently insert the cutting into your soil blocks, seed trays, or cells until the remaining leaves sit above the soil and then firm at the base. Keep the soil moist and use plastic bottles, clear domes, plastic bags, or kitchen cling wrap to maintain the humidity, venting daily. Do not let the plastic touch the leaves. Heat mats are useful in accelerating rooting. Most cuttings will root in three to six weeks, sooner if kept in a greenhouse. You’ll know when your cuttings are rooted by lightly tugging on them; if they resist being pulled, they are rooted.

Hardwood cuttings are typically six- to-eight-inch, pencil-thin lengths cut at an angle below a node at the bottom. Make another cut at the top, this time straight, above a node. The straight and slant cuts will help you differentiate the top from bottom of the cutting. Wrap branches in damp paper towels to maintain freshness until you’re ready to plant. Smother the bottom of each in rooting hormone and insert two-thirds to three-quarters inch deep into a pot filled with soil mix, water, and place in a cold frame or greenhouse over the winter. Remember to check periodically to ensure your cuttings are moist throughout the cooler weather. For gardeners in warmer climates (zone 8+) you can keep your cuttings outside until the spring, but they may take longer to root. Over the next six to eight months you should see new growth. Tug to make sure they are rooted, and it’s now time to transplant into the garden.

Check regularly for water and moisture. The soil medium should be moist, not wet; otherwise you will see a disease called Black Leg. Basically this is rot, starting at the base and going up. You will know you have this if you see the bottom of the stem turn black. It is important to maintain humidity, hence the plastic domes or bags, but if the plastic touches any leaves it will invite mildews, rots, and disease. Also, you should vent periodically to prevent condensation buildup on the interior of the plastic.

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