By Jill Henderson – Show Me Oz
Now that summer is almost over, it’s time to start thinking about repotting, transplanting and dividing perennial flowers and herbs. So often, we wait until spring to move or propagate new plants. But by taking care of those chores now, you not only sidestep more work during the busy spring season, but you also give your new plants a big head start on next year’s growth.
Almost any mature perennial herb can be divided into two or more new plants with little effort through a process known as root division. Herbs may be considered mature when they are at least one year old and well established. Keep in mind that some herbs can grow in the same place for a few years and never attain their full size. These herbs should be transplanted to a more favorable spot in the garden – not divided.
The tools needed to divide herbs include a shovel or sharp spade, a small knife, a pair of scissors, and perhaps a tarp to work on. If you plan to pot the new herbs, also have on hand several sizes of pots, a bag of potting mix, and plant markers.
How many new plants you get from the original depends on the size and vigor of that plant. One way to determine the number of divisions that are possible is to dig up the entire plant and observe the roots. Each new division must have a healthy network of roots attached to a viable stem or stems. Without these, the new plant may not survive the shock of division.
For herbs that grow in mounds or clumps, such as lemon balm, hyssop, savory and tarragon, the entire plant can be lifted from the ground and literally cut in half using a strong, swift thrust of a sharp spade down the center. Another approach is to divide the plant prior to digging it up. To do this, leave the plant in the ground and, using a sharp spade, cut the plant down the center in one clean motion. Carefully lift the two divisions and further divide or replant.
Some gardeners prefer a surgical approach to plant division. After lifting the plant, use a sharp knife to cut it in two from the surface to the roots. This methodical approach definitely gives the gardener more control over where the crown is cut and the proportion of roots to each stem or crown.
Herbs that grow in large masses with extensive root systems or rooting stems, such as thyme, mint and catnip, are easy to divide. To allow for easier handling and observation of the stems, cut the foliage back by two-thirds and then cut circular or square “plugs” from the bed using a sharp trowel or knife.
For plants with large roots or rhizomes, such as ginger, turmeric and horseradish, dig up the plant and trim back the foliage to a manageable size. Larger rhizomes will have natural folds and segmentations that are easily broken off. Select as many of these sections as desired and replant them in pots or directly in the garden. Make sure to set the rhizomes so that they lay horizontally in the soil and that any “eyes” or stems are facing upward. Horseradish can be treated similarly except that the root segments are replanted vertically, with the pointed end facing down. The best times to divide rhizomes are during fall harvest or in early spring after growth has begun.
Garlic is a specialized bulb with many toes or cloves that are easily separated from one another. To divide garlic, begin by selecting the largest, healthiest bulbs. Separate the cloves, leaving the skin around each toe intact as much as possible. For large bulbs, plant only the largest of the cloves. Plant each clove 6 in. (15 cm) deep, with the pointed end facing up. Garlic grows best when planted in late fall before the first frost. This gives the bulbs plenty of time to grow.
Another method of propagating herbs and flowers is called layering. Layering involves rooting actively growing stems while still attached to the mother plant. This system is ideal for plants that have are net yet big enough to divide. Layering is most successful when applied in the spring or early summer, while herbs such as sage, savory, hyssop, rosemary and tarragon are adding fresh new growth. But if you layer in late summer or early fall, the stems will have all winter to develop a healthy root system and will be ready for transplanting in early springTo layer a perennial herb, begin by selecting long, flexible stems. You can layer as many stems as you like, provided you allow enough room between for each to grow their own root system. Whenever possible, select stems that are young and green. Depending on the plant, woody stems will often root, too, if given enough time, but they should also be as young as possible. Older stems often don’t root well.
Once you have selected one or more stems to root, simply bend them gently to the ground, taking care not to break them or injure the joint where they meet the mother plant. Strip off all but the topmost leaves and bury most of the stem under 3 to 5 inches (8 to 13 cm) of soil. Use a small rock or other device to pin the stem firmly to the ground. Be sure to leave the leafy portion of the stem protruding 2 to 3 in. (5 to 8 cm) above the soil. If necessary, temporarily prop the leafy tip upright with a small stone or stick until it begins to grow on its own.
Over time the stem will root and eventually be able to survive on its own without the nourishment from the parent plant. In the spring, minor rooting is often accomplished in 6 to 8 weeks. In late summer through winter, this could take a little longer, depending on the weather. To ensure that the layering will survive winter, do not cut the stem that connects the two plants or attempt to transplant the new start until the spring of the following year. A good layer of mulch will help keep the rooting stem warm and moist.
Herbs such as mint, thyme, oregano, sage and marjoram can all be propagated using layering. These herbs tend to sprawl or creep, and most of them will naturally root where they touch the soil. Simply covering the existing stems with 1 or 2 in. (5 to 8 cm) of soil can speed up this natural process.
While I this article is geared towards herbs specifically, some shrubs and perennial flowers can also be propagated using these methods.
Once you become familiar with propagation methods such as division and layering, you can quickly and easily increase the number of valuable plants in your garden without any added expense and you don’t have to wait for spring to do it!
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