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PROPAGATING HERBS FROM PERENNIALS

Fertilizing Guideline

Contrary to some popular beliefs, herbs will appreciate well balanced fertilizer in moderation; soil that is too poor will produce foliage that is sparse and has poor flavor. When fertilizing, however, remember that a too rich soil will generate lush growth with only small concentrations of oil in the leaves.

PROPAGATING THE PERENNIALS

There are several ways to increase perennial herbs once they are established in the garden or in containers. You should find that all methods are easy to do and give a high percentage of success.

Stem Cuttings

Rooting stem cuttings or "slips" is perhaps the simplest method for propagating perennial herbs and often is faster than growing the same herbs from seeds. Herbs such as feverfew, lavender, lemon balm, rosemary, pineapple sage, winter savory, and southernwood grow well from stem cuttings. Mints are particularly responsive, rooting in only a few weeks, so if the practice is unfamiliar to you try a favorite variety of this herb first.

The cuttings can be taken any time in the spring or summer during the active growing season; take them from healthy, well-established plants. Strong, new tip growth makes the best cuttings. Do not take the soft or forced growth that results from too little light, weak shoots from the center of the plant, or exceptionally vigorous growth with thick stems. Stems that snap when bent sharply-rather than those that bend without breaking-give the best results.

Make the cutting just below a leaf bud or node, using a sharp knife, razor blade, or shears to make the cut. The cuttings should be between 8-15cm  long and have good foliage on the upper end.

Between the time you cut the stems and plant them, keep the cuttings out of the sun between two layers of damp cloth or paper towels to prevent them from drying and wilting.

A good propagation soil mixture is two parts sand and one part vermiculite. If you are rooting a large number of cuttings, a nursery flat makes a good propagating bed. For just a few, you can use a clay pot or an empty coffee can. Be sure that whatever container you use has provisions for drainage.

Thoroughly moisten and drain the mix, then fill the container to within about 1cm of the top, firm well, and level the surface. Before inserting the cuttings, strip the leaves from the lower 1/2 or 1/3 of each stem, and dip the cut end in a hormone powder to stimulate root growth. Place the defoliated ends into the soil about 1/2 or 1/3 the length of the stems and water gently to settle the soil. Cover the cuttings with a plastic bag or an inverted glass jar to keep the soil moist and the humidity high. Occasionally raise the jar or remove the cover to admit fresh air and to prevent molds and fungus from forming. Set the cuttings where they will receive good light but not direct sunlight, and turn the containers to give the cuttings equal light on all sides.

The quicker rooting herbs such as lemon balm, thyme, and basil usually take from 4 to 6 weeks to form roots. Herbs with especially woody stems such as rosemary, myrtle, artemisia, santolina, and germander may take several months.

When roots have formed, the foliage will gain a bright green color and, although there probably will not be any new leaves, the cuttings will then be ready for transplanting into individual pots that are about 8-10cm in diameter. Be gentle when you lift newly rooted plants and, if you can, leave some of the original propagating mix around the roots (or put a little bit in the planting hole in the new container). Until new growth starts, keep the herbs out of the sun and the soil moist.

As soon as roots begin to poke through the drainage hole in the individual pots the plants are ready to be transplanted into larger containers or into the garden. Follow the transplanting procedures described here.

Layering

Layering is perhaps the simplest method of increasing many of your perennial herbs such as mints, sage, thyme, winter savory, marjoram, lemon balm, santolina, and rosemary. It is a simple method in which branches are brought into contact with the soil, causing them to take root while still attached to the parent plant. Many herbs, in fact, layer themselves naturally from branches that creep along the ground.

Select a vigorous branch growing close to the ground or one that is flexible enough to bend down to the soil. Bend it down and select a section about 30cm from the stem tip and just below a leaf node. Directly below this part, dig a shallow hole, and mix the soil with equal parts peat moss or ground bark and sand: It is here that you will bury the stem so that it will form roots.

On the underside of the branch at the part that will be buried, make a slanting cut half way through (on slender stems simply scrape away the outer layer of the surface) and put some hormone powder on the cut or scrape to stimulate root growth. Next, bend the branch down into the hole and anchor it in place with a heavy wire loop or staple. Bring the end of the branch to a vertical position and stake it upright. Finally, fill in the hole, firm down the soil, and water thoroughly. To keep the soil firm and help maintain moisture, place a brick or stone on the surface directly above the layered stem section.

When layering in the fall in cold winter areas, spread a mulch over the layering to protect it, leaving only the tip and several leaves exposed.
Roots may form in as little as 6 weeks for many herbs. Check for root growth by carefully removing the soil from around the stem. When roots are well established, sever the stem from the parent plant and move your new plant to its garden location or container.

Root Cuttings

You also can take root cuttings from any plant that sends up new stems from its roots. This includes catnip, horehound, rosemary, savory, myrtles, sage, lemon verbena, germanders, thymes, lemon balm, artemisia, and tarragon.

Select roots 5-10cm in diameter from vigorous plants and cut them into pieces 3-9cm long. Fill a box or flat to within about 2.5cm of the top with light garden loam and place the cuttings 5cm apart in a horizontal position on top of the soil. Cover with about 1cm of additional soil, and water thoroughly. Cover with glass or newspaper and place in the shade. When new growth and leaf buds appear, remove the covering and transplant each cutting into individual small pots, or transplant them into a deeper flat about 15-20cm apart.

Root Division

Each year the roots of many perennials grow and spread, sending up new growth that increases the size of the plant. These new roots are capable of becoming independent plants when pulled or cut apart from the parent. Chives and tarragon are examples.

The best time to divide is in the autumn or early spring, when plants are not forming new growth. Dig the herb up from the ground and simply pull or cut the root clump into sections. After dividing, replant the sections into the garden or containers as soon as possible, and keep the soil moist until the plants have adjusted.

POT BOUND CLUMP of chives has mass of tangled roots that can be separated into several separate plants.

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