The easiest and fastest way to generate new plants for your landscape is to divide fully grown, herbaceous (non-woody) perennials that are already in your garden. Each division will make a new plant for your own garden or to share with friends.
Division also helps control the size of aggressive plants and rejuvenates old or overcrowded plantings, so they grow more vigorously and bloom more freely.
Best candidates: Not all plants can be divided. Divide only fully grown, herbaceous perennials—plants that have fleshy aboveground growth as opposed to woody stems. The best herbs for division include artemisia, bee balm, catmint, catnip, chamomile, chives, chrysanthemum, echinacea, geranium, horehound, iris, lady’s mantle, lamb’s ears, mints, oregano, primula, sweet woodruff, tarragon and yarrow.
When: Plants can be divided in early spring or fall, depending on when they flower. Divide fall bloomers in early spring, after the growing tips have emerged; divide spring and summer bloomers in fall, when cooler nights have set in.
A good rule of thumb is to divide and replant herbaceous perennials that have grown vigorously for several years but now have barren or dead centers, have sparse or poor bottom foliage, or whose flowers have become smaller or less abundant than usual. Generally, this is every three to five years.
How: The method is the same regardless of the plant and its type of root system. You’ll need a spade or garden fork, a sharp knife and garden shears.
1. Dig up the plant on a cloudy day, keeping as much of the roots intact as possible. Remove or shake off any loose soil so you can easily see the crown and roots. (Click here to see an illustration.)
2. Divide the plant into smaller pieces using the knife or garden fork to cut through the crown and roots. (You might need two garden forks to pry apart roots of extremely overgrown clumps.) Each division should have at least two to five vigorous shoots with ample roots attached. Remove any diseased or discolored portions. (Click here to see an illustration.)
3. Cut back the top growth to about 6 inches or half the plant’s height.
4. Replant or pot up your new plants immediately and water well. (Leave the top of the rhizome exposed when replanting iris divisions.) To give plants a strong start, amend the new garden area with compost before planting. (Click here to see an illustration.)
A frequent contributor to The Herb Companion, Kris Wetherbee grows and propagates herbs in the hills of western Oregon.
Click here for the original article, Cut, Divide & Conquer: A Guide to Propagating Herbs .
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