Expert answers to your herb-growing questions.
Q. This year I want to grow some of my herb plants from seeds. What are the steps to starting seeds over the winter?
A. Seed starting is like baking bread—you need the right mix of ingredients, the right temperature and viable yeast. In the case of seed starting, the ingredient list includes a lightweight growing medium and containers for planting. Provide the right temperature with a warm greenhouse or sunny window; and seeds, of course, are the viable catalyst.
Use a commercial potting mix or seedling mix for the growing medium. Choose from egg cartons, yogurt cups, flats of six-cell packs or small pots when it comes to containers. (Note: Fiber- or peat-based pots should be soaked well before adding soil.) Like yeast, seeds have a limited life—be sure the seeds are fresh or packaged for the upcoming growing season for optimum germination.
The directions on the back of the seed packet will tell you all the specifics for starting that particular seed, along with germination time, spacing and transplant information. Be aware that germination time will vary during winter. Some herbs (parsley is an example) can take up to a month to germinate. Soaking seeds overnight often will help speed
Fill pots or flats to within 1/4 inch of the top with moistened potting or seedling mix. Plant seeds according to package instructions, paying special attention to whether seeds should or should not be covered. (Some seeds need light in order to germinate.) Use a fine sprayer to moisten the soil and keep it continually moist until seeds have germinated. Then, place pots in bright light or set them just a few inches below fluorescent bulbs to produce strong, healthy plants. Small pots dry out quickly, so check often and keep the soil slightly moist. Fertilize with a weak solution of liquid organic fertilizer when seedlings are about an inch high, then transplant into larger pots as needed. Most seedlings can go in the ground after all danger of frost has passed.
Q. Every year I start basil from seed without any problem. But last spring I tried growing echinacea from seed with no success. Do you have any tips for starting echinacea from seed?
A. Echinacea requires more specific germination conditions than basil. Try your hand with Echinacea purpurea first; it’s the easiest echinacea to grow from seed.
For best results, start the seeds indoors or in a greenhouse in January or February. You can increase the germination rate with a treatment called stratification—exposing seeds to cool, dark, moist conditions for a period—before you sow them.
First, mix the seeds with a small amount of pre-moistened peat moss or vermiculite. Place them in a snap-and-seal bag, then refrigerate for a week or two. Or simply scatter the seeds between two layers of moist paper towels, put the towels in a plastic bag, then refrigerate.
After this chilling period, remove the seeds. Sow them in flats or cell packs on the surface of a well-drained, commercial potting mix. Germination occurs in 10 to 30 days. Once the seeds start to sprout, lightly cover the seeds with a thin, 1/8-inch layer of fine potting mix or vermiculite. For best growth, keep seedlings beneath grow lights or fluorescent lights. Transplant seedlings to your garden in May or June.
Stratifying seeds is not essential for successful germination of E. purpurea, but it is a must for other species. Seeds for narrowleaf echinacea (E. angustifolia) and pale-purple echinacea (E. pallida) require a longer stratification period, from three to six weeks. Stratify seeds for yellow echinacea (E. paradoxa) and Tennessee echinacea (E. tennesseensis) from four to eight weeks.
You also can try planting E. purpurea seeds directly in the garden in early spring, about six to eight weeks before your last spring frost, or when soil temperatures reach 55 to 70 degrees. Be sure to lightly cover the seeds with a thin layer (1/8 inch) of compost or vermiculite. This method is much easier than starting the seed indoors, but getting good germination is not guaranteed.
Q. I’m thinking of starting an indoor herb garden but have heard whiteflies can be a problem. What are they and what can I do to keep my plants pest-free?
A. Whiteflies are tiny insects that resemble flat, waxy scales when young. Adults have wings and look more like tiny white gnats or minuscule moths. They gather on the underside of leaves or fly about like miniature white snowflakes when disturbed. Members of the mint family—such as oregano, sage, thyme, marjoram and mint—are most susceptible to these leaf-sucking pests.
The easiest way to protect your plants is to treat them before you bring them indoors. A quick dip in soapy water will help dislodge and destroy any unseen eggs. Use a natural dishwashing liquid at a ratio of about 2 teaspoons to 1 gallon water.
If whiteflies do show up indoors—perhaps by hitching a ride on new plant additions or emerging from potting soil—your best offense is a good defense. That is, provide the best growing conditions for your herbs while creating an inhospitable environment for whiteflies. These pests thrive in dry, indoor air conditions, so give them the opposite: Boost air circulation by running a small fan, and mist plants weekly.
Control mild whitefly infestations with yellow sticky traps or insecticidal soap. Both are widely available at garden centers and are safe to use on edible plants. Be sure to cover all surfaces of the plant with the spray. Repeat sprayings (according to label instructions) until pests are eliminated.
Q. I’m anxious to start my first herb garden, but it’s still a few months until spring. What can I do in winter to start planning?
A. Start with a wish list, then devise a planting strategy to make that happen. For example, do you want a cutting garden, dye garden, ornamental herb garden or do you crave fresh culinary herbs for the kitchen? Map out a space for an herb garden that is both easily accessible and aesthetically pleasing. A fragrant courtyard container garden, a culinary herb garden that can be viewed from your kitchen window, or even a window box garden for butterflies might work best for you.
When mapping out a planting strategy, remember to group like herbs together—some herbs like it sunny and dry while others thrive in a shady, moist environment. Consider a plant’s height, color, texture and shape. Use the tallest plant to form the backdrop in a bed or border, or as the central focal point in an island bed. Repeat a plant’s form or color to bring a sense of harmony to the space.
A frequent contributor to The Herb Companion, Kris Wetherbee grows herbs in the hills of western Oregon.