By now your garden honey-do list is probably getting pretty long, but if you haven’t done it yet, now is the absolute best time to propagate perennial herbs and flowers through cutting, layering and division. Vegetative propagation is best achieved during periods of active growth such as spring and fall, with spring being the best season overall. During this time the plant is filled with growth hormones in the stems and roots, and you can take advantage of those natural growth stimulators to multiply your mature plantings. This article on herb propagation comes from my book, The Healing Power of Kitchen Herbs.
Many herbs can be started easily from seeds, but others, such as bay, rosemary, and specialized cultivars of more common perennial herbs cannot. This is also true for bulbous or rhizomatous herbs such as garlic, ginger, turmeric, and horseradish, which don’t reproduce well, or at all, from seed. Also, when starting certain herbs from seed, the resulting seedlings may have varying levels of fragrance or flavor that aren’t readily apparent until the plant is mature. If you are growing your herbs for culinary or medicinal uses, it’s nice to be able to count on consistent quality year after year. By reproducing plants through vegetative propagation, you essentially make a clone of the mature parent plant, assuring that the new plant will be just as wonderful as the parent.
As I mentioned earlier, there are several methods of plant propagation, but today our focus is on root division as a method of propagating herbs.
To begin, it is important to note that almost any mature perennial herb can be divided into two or more new plants with little effort through root division. An herb is considered mature when it is at least one year old and well established. It is important to note that some herbs can grow in the same place for a few years and never attain their mature size. These herbs are obviously struggling in their present position and should be transplanted to a more favorable spot in the garden to continue its growth rather than being 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 very carefully dig up the entire plant and observe the root system. Each new division must have a healthy network of roots attached to a viable stem or crown. Without these, the new plant may not survive the shock of division. You can choose to divide the plant in as many parts as possible, which will give you lots of small “starters”, or you can divide the mature plant in two or three, leaving you with several fairly large ones. The former is great for expanding a large planting bed, while the latter works best when quick productivity is the priority.
For herbs that grow in dense 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. Break the cloves, apart, taking care not to break open the papery covering. Pick out only the largest of the cloves for planting and use the rest in the kitchen. 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.
So, now that you know how to divide plants, put this chore on the top of your spring garden to-do list and you will be rewarded with a bountiful supply of new herbs and flowers for your garden with plenty to share. Next time we’ll discuss layering…
You can find this book in our bookstore.
Jill Henderson is an artist, author and the editor of Show Me Oz
Copyright Jill Henderson – All Rights Reserved