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If you want to increase the plant supply in the garden, August is a great month for taking cuttings of softwood or semi-soft wood. Some plants, such as hardy fuchsia, root easily if just tucked into a glass of water. Most, however, need a rooting medium. Some plants that grow well from softwood cuttings are Euonymus, Fatsia, Forsythia, Hebe, Hydrangea, Lavender, Mahonia, Nandina (early August) Osmanthus, Salix (willow), Skimmia, and Weigela. If you've admired a shrub in a friend's garden, think about propagating it now. Perhaps you can trade weeding services for a few choice twigs. A helpful small book on this subject is "Cuttings Through the Year" edited by Joy Spurr, 1980, available from the Washington Park Arboretum Gift Shop in Seattle.
When gathering softwood, check the condition of the twig. You are selecting cuttings of about 4 inches in length from the tip growth of the branch. ‘Softwood' twigs will break off crisply with a snap. Earlier, when too young for successful rooting, they don't break off neatly, but crush between fingers. If the plant is too old, the wood will bend but not break off. ‘Hardwood' cuttings taken from older wood are generally propagated in late fall and winter. Forsythia is a good plant to practice taking cuttings on, because the branches are easy to manipulate and to feel the difference between last year's hardwood and this year's softwood, wood that has grown in the current season.
Before gathering cuttings, prepare clean containers. Keeping hands, tools, containers, and rooting medium clean helps with success in propagating plants. Choose a pot with good drainage, or if you will be doing many cuttings, a nursery flat. Cut sticks for the edges of the pot or flat to support a plastic cover. Sometimes people build miniature greenhouses using hoop supports of heavy wire or plastic pipe.
Many different types of soil mix will work for creating cuttings. The purpose of the mix is to support and hold up the twig until it roots, to retain water and to provide air to the cutting. There aren't any nutrients or fertilizer needed in the mix, because the plant will be moved into a growing mix with fertilizer once it has rooted. A plant without roots can't use fertilizer. The rooting mix must drain well so the plants won't rot, and must hold water to help prevent drying out.
Usually rooting mixes contain some form of organic material: fine wood chips, peat moss, or bark chips. Some mineral component, such as coarse sand, pumice, perlite, vermiculite, or grit is also added. There aren't any "perfect" mixes, though a blend of ½ sand and ½ peat moss works well, or ½ pumice and ½ peat moss. Coarse particles are essential for air flow but the twig must be firmly in touch with the mix and supported by it.
Start with clean ingredients for the mix. A fresh, unbroken bag of peat, perlite, pumice, or vermiculite will be clean enough for use. Don't use anything that's been sitting around outside or in a pot for months or years gathering microorganisms that can cause diseases. The mixture will never be ‘sterile' but the objective is to avoid using something contaminated with disease organisms. It's not necessary to be compulsive about this, but be as careful as possible. Wet the mix thoroughly before inserting cuttings. Let the mix soak, then drain it. A dry spot in the mix will kill the roots emerging at that point so thorough wetting is vital.
Select healthy cuttings from the ends of this spring's growth. Four inches is about the right length. After all, the plant will have to survive rootless for a while, and a tall, wobbly cutting full of leaves won't stand the strain.
If there will be some delay before getting cuttings into soil, place them in plastic bags, sealed with a wrap of wet paper towel around the bottom. Keep them out of heat and sunlight, since a steamy cutting is a cooked cutting. Many experienced gardeners place the baggies in a small cooler to keep the temperature lower during transport. (Ice isn't necessary.) If taking a lot of cuttings, be sure to bundle or mark them so that the top and bottom are clear; a cutting inserted upside down, opposite from its growth pattern, won't grow as well.
When ready to pot the cutting, strip the leaves from the bottom two inches (don't ever stick existing leaves under the soil mix where they will rot.) Using a clean, sharp knife, scrape the bottom inch of the cutting. The wounded tissue will be stimulated to produce roots. A rooting hormone can help. Dip the end of the cutting in water, and then in a rooting hormone, which is a synthetic plant hormone. Pour a small amount of rooting hormone into a cup and dip into the cup, rather than directly into the jar. Discard the used material at the end of the working session. (Dipping into the jar itself can cause contamination.) Buy a very small quantity and replace it each year so that you are starting with fresh material for rooting.
Make a hole in the mix with a pencil or chopstick, insert the finished cutting, and firm the soil around it. Water very gently when the container is full.
Cover the container with plastic, placing it in a light area with NO DIRECT SUNLIGHT. Check to be sure it stays damp, and after about 2-3 weeks, tug gently on twigs to feel for roots. Remove any rotted cuttings immediately. Some people choose even simpler supplies: rose cuttings do well in a pot with sand, covered with a glass jar.
Pot up, protect from winter cold, and enjoy the thrill of creating your own garden shrubs. In my garden, buddleia, senecio, weigela, and lavender now full grown began as twigs in a pot several August ago. Getting something for nothing pleases most gardeners, and if the process fails, you'll have a much greater appreciation of the skill of nursery propagators.
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