Propagating Herbs From Cuttings in Plug Trays

Nurseries use plug trays to start plants from seeds or cuttings.

Nurseries use plug trays to start plants from seeds or cuttings.

Plug trays allow you to produce large numbers of cuttings to rapidly increase your stock of herbs. Try to choose plug trays with fewer than 72 cells because these generally have more space between cells to allow the cuttings to grow more quickly. Because you can fill the cells with your own potting mix, you can keep propagation costs down.

Growing Medium

You can use a commercial or homemade growing medium for the plug trays. Avoid using only coarse sand, which you may use in standard planting flats, because it tends to fall through the drainage holes at the bottom of the cells. An equal mixture of peat moss, sand and perlite, or a combination of any two, works well as a growing medium for propagating herb cuttings in plug packs. Peat moss retains the moisture around the cutting and the sand allows excess water to drain away. The peat moss and perlite aerate the planting medium so roots grow unrestricted.

The Cuttings

Some herbs, such as French tarragon (Artemisia dracunculus), are generally propagated through cuttings because the plant produces few seeds and the roots are fragile. Rooted cuttings produce a clone of the parent plant. Take herb cuttings in the early morning, when they are at their peak of moisture content. You will have better results with stem cuttings that have no flowers or buds. The cutting needs at least one leaf node at the basal end for root growth and a leaf or a pair of leaves at the top for photosynthesis to take place. The cuttings fit better in the plug tray when the rest of the leaves on the stem are removed. Cut the leaves in half horizontally if the leaves of the cuttings still touch. Most herb cuttings are considered soft wood or green cuttings and need little stimulation to produce roots. Certain herbs, such as lavender (Lavendula spp.), root better when dipped in a rooting compound before planting. Both liquid and powder forms work well to stimulate root growth.

Benefits of Plug Trays

Plug trays work well to propagate herb cuttings because each cell is deep enough, generally 1 1/2 to 2 inches, to hold the cuttings so there is less chance of the stems falling over when handling the tray. The drainage holes are large enough that you can water the cuttings from the bottom, so moisture stays in the soil and not on the leaves. The cells are uniformly spaced so you can evenly divide the tray if you propagate more than one type of herb. Use plug tray covers to create a propagation chamber for the cuttings. If you don't have a cover, invert a clear or opaque plastic bin over the plug tray and achieve the same results.

Growing Herb Cuttings

The environment for the cuttings must be bright, moist and humid but not too hot. The ideal temperature is about 70 degrees Fahrenheit. Sterilize the plug tray with bleach and rinse with clean water. Fill the cells with the growing mix and moisten the mix by setting the tray in a tray of water. Remove the tray when the top of the mix is damp. Dip the cuttings into a rooting hormone, if you use one, and stick each cutting into a cell as deep as the cutting will go. Adjust the leaves so they are not touching and cover the tray. Set the entire tray in a bright window or under a grow light. The humid environment is a good breeding ground for disease and fungus. Keep problems to a minimum by removing the cover every day to refresh the air in the propagation chamber. The cuttings should root within three or four weeks. Once the roots form, you can transplant the new herb plants.

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