also valuable for gardeners with small yards and for people forced to grow edibles in containers because their soil is infested with nematodes or root rots. In addition, as containers can be brought inside, in harsh-winter areas container growing may be the best way to grow tender perennials like rosemary and sweet marjoram.
How to Grow Herbs in Containers
After years of trial and error, I've found five secrets for success with growing herbs in containers:
1. I use only soil mixes formulated for containers. I've found that garden soil drains poorly and pulls away from the sides of the container, allowing most of the water to run out, and it is often filled with weed seeds.
2. Since containers must have drainage holes in the bottom to prevent the plant from drowning, at planting time I cover the holes with a piece of window screening or small square of weed cloth to keep dirt in and slugs out. (New evidence indicates that gravel or pottery shards in the bottom actually interfere with drainage.)
3. In hot weather, I now use only large containers, those large enough to provide generously for the plant's root system and hold enough soil so that the plant needs to be watered less often. I find that a small number of the small herbs like chives and thyme will grow in twelve-inch containers, but most grow best in large containers (eighteen inches or more in diameter). My Southern friends report that in their climate large containers are mandatory, as the roots on the south side of small pots bake in the hot sun.
4. After years of pale plants, I find I need to fertilize frequently and evenly. For me, biweekly doses of fish emulsion work well, as do granulated fish meal and slow-release fertilizer granules renewed every six weeks or so.
5. I find the most difficult aspect of container growing is to maintain the correct moisture in the soil. Succulent herbs like basil and chervil suffer when not watered enough; on the other hand, the Mediterranean drought-tolerant herbs succumb to root rot if given too much water, especially the sages. Once I learned how to water properly, I was on the road to success.
All gardeners need to learn to water container plants properly; even in rainy climates, hand-watering containers is usually a necessity, as little rain penetrates the umbrella of foliage covering a pot. I find that when I hand water, it is most helpful to water the container twice. The first time premoistens the soil (I think of it as moistening a dry sponge), and the second watering is when I feel as though I am actually watering the soil. The opposite of underwatering is overwatering. To prevent this, I test the soil-moisture content with my finger before watering.
Herbs make handsome container plants. They are compact, have a lovely range of foliage colors and textures, and most bloom at least once a year. Here the foliage of a purple sage contrasts with yellow and orange nasturtium flowers, and the spiky texture of the chives sets off the rounded nasturtium leaves.
Watering container-grown herbs is critical for all gardeners, but it's of even greater importance for those of us who live in arid climates. After years of parched-looking plants, I finally installed a drip system. What a difference! I use Antelco's emitters, called "shrubblers" (available from plumbing-supply stores or by mail order from The Urban Farmer Store, 2833 Vincente Street, San Francisco, CA 94116), as they are tailored so each container on the system can have the exact amount of water it needs. My drip system is connected to an automatic timer, so it's scheduled to water every night for five minutes from spring through fall.
Overwintering Herbs Indoors
As you can see, growing plants outside in containers has its challenges, and the problems are exacerbated when you bring the plants inside for the winter. In essence, you change a plant's environment from a bright, sunny spot with fairly high humidity and a normal ecosystem and relocate it to a dim area with low humidity and no natural predators. It can be done, and done well, but it requires care, thought, the right plants, and a suitable sunny spot in the house. As a rule, herbs that tolerate shade are the most successful. If you plan to cook with many of the herbs, you will need more plants than usual, as herbs grown indoors over the winter grow more slowly than those outside.
It's late spring in my garden and time to pot up young tarragon, lavender, and scented geraniums before the weather gets too hot and they need water twice a day. A harvest of curly parsley, to make a lovely cream soup, oregano for drying, and the purple flowers of the Mexican sage (Salvia leucantha) for a table bouquet, complete the scene.
Containers can become the focal point of a garden. Here an old wooden bucket filled with golden sage and a nail barrel with ornamentals and creeping rosemary draw the eye. In the background the flower spikes of anise hyssop attract bees, and in the foreground a winter savory peeks out from behind a species yellow marigold.
1. Select a place in the house that gets at least six hours of direct sun a day. Temperatures in the sixty-to seventy-degree range and areas away from cold drafts are best. If a sunny window is not available, then set up an area with fluorescent lights. Locate fixtures six inches above the plants, and run them for sixteen hours a day.
2. Choose herbs that are fairly adaptable to indoor conditions, such as mint, parsley, winter savory, lemon balm, and scented geraniums. Chives grow fairly well indoors but tend to go dormant for part of the winter. If you have an attached greenhouse or bright sunroom, you might try the sun-loving bay, oregano, rosemary, sweet marjoram, and thyme as well.
3. For the best success, choose your plants at the beginning of the growing season and plant them in containers from the outset instead of uprooting them in the fall. Containers at least eight inches across filled with commercial potting soil do best. These containers can be sunk in garden soil over the summer to keep watering to a minimum.
4. A few weeks before your first expected frost, prune back plants; check for aphids, scale, whiteflies, and mites; and treat if infested.
5. Place plants in a shady spot for a few weeks to acclimatize them to low light levels.
6. Just before bringing plants in, wash remaining foliage well and spray with a prophylactic dose of insecticidal soap.
7. Once they're inside, isolate outdoor plants from your houseplants until you have determined that neither is contaminated.
8. Water most overwintering plants only when the soil surface starts to dry out.
9. Wash down foliage occasionally to remove dust that can harbor spider mites.
10. Turn containers every week or so, so all sides receive equal light.
11. Fertilize monthly with half-strength fertilizer.
12. Maintain good air circulation and keep plants from touching, to prevent diseases and pests.
13. If your house is very dry, raise the humidity around your plants by filling a shallow tray with pebbles and placing it under your plants. Pour a half inch of water into the tray every few days. Keep containers from sitting in the water, to avoid root rot.
14. Watch for pests; if they appear, immediately isolate any infested plants to prevent the problem from spreading, and treat them with insecticidal soap or send them to the compost pile.
Two
