There is good news and bad news about growing herbs in Tucson. The good news is that we can grow herbs all year. The bad news is that they may not be our favorite herbs. As the days heat up, remove winter favorites and plant summer herbs. There are also many year-round herbs great in the landscape.
By looking at plant families, it is easy to know what to expect from your herbs. Some families came from the tropics and can stand the heat, others get out of the kitchen. Some herbs live for years in the lands where snowbirds come from, but only live from October to May in Tucson. Higher temperatures cause many herbs to bolt. Bolting is a gardener's term for sending up a flower stalk, setting seed, then dying. Come to think of it, using the non-gardeners term, many snowbirds bolt about this time of year too.
Herbs that bolt in Tucson's spring are those in the carrot family; cilantro, dill, parsley, fennel, caraway. Harvest and dry the leaves, or wait and collect seeds. Butterflies love to visit these flowers so leave a few plants for them.
Some members of the lily family flower now, but survive underground if you don't get around to harvesting them; onion, garlic, chives, and the delicious Tohono O'odham bunching onion, I'itoi onion. Despite their family name, some of the sunflower family quit as it heats up, German chamomile and calendula for example. They put on a last frantic show of blooms before succumbing. Deadhead old flower heads for longest performance. (Dry the flowers for herbal tea!)
Parsley is gone, but sage, rosemary, and thyme remain. They and many other members of the mint family can take the heat; basil, oregano, marjoram, germander, lavender, lemon balm, bee balm, horehound, hyssop, anise hyssop, catnip, catmint, and, well, mint. Despite the name, Mexican mint marigold is not a mint, it's in the sunflower family, along with yarrow, feverfew, echinacea, comfrey, and Roman chamomile. Other heat-loving herbs include chilitepenes, garlic chives, society garlic, bay, lemon grass, lemon verbena, and a personal favorite, caper.
From south of the border, herbs for summer include annual epazote Chenopodium ambrosoides, a musky smelling herb whose leaves, when cooked with beans, eliminate the need for Bean-o. Perennials with anise flavor, hoya santa Piper sanctum has large heart-shaped leaves while Mexican mint marigold Tagetes lucida has narrow, gland-dotted ones. The mint marigold has many names, Texans named it Texas tarragon, Floridans call it winter tarragon, and in Mexico it's pericon. As you may guess, it tastes like tarragon -- plus it grows better in Tucson than the tarragon from France.
How to care for all these herbs? Let's look at family trees. Tucson summer herbs come mostly from the warm cradles of ancient civilizations; Mesopotamia, Egypt, Israel, Greece, Mexico. They generally prefer full sun situations, perhaps with afternoon shade, plus well-drained soils. Well-drained soils are key to healthy herbs. Other than a few aquatic herbs, most cannot tolerate wet roots. Allow the soil to dry fairly well between watering -- but not bone dry.
Check your soil by wetting it thoroughly then let it dry for an hour. Scoop up a fist full and squeeze it. It should feel damp but not be dripping wet. Open your palm. The clump should crumble slightly, but not fall completely apart. Gardeners call this loam. If the soil clump stays a solid clump, it has too much clay. If it collapses completely to bits, too much sand. For soil high in clay, amend with sand and organic matter. For sandy soil, add organic matter and possibly topsoil. Organic matter is compost, which can be made or purchased at a nursery. To keep herbs in pots, potting soil with added sand works well.
Many herbs are excellent for landscaping. For example, rosemary, used all over Tucson as a groundcover. Originally from the eastern Mediterranean (Greece, Turkey) it's adapted to surviving hot summers after only winter rains. This doesn't mean you shouldn't water it or give it shade. In the hills of Turkey, it crouches around boulders or on cliffs where it can sink its roots deep into soil shaded by rocks, and pick up moisture in crevices. Germander, a cousin to rosemary, is used much the same way in the kitchen but in the landscape it offers tiny, round, glossy, forest-green leaves instead of blue-green, needle-like leaves.
Consider a landscape with sage, thyme, oregano, marjoram, germander, lavender, lemon balm, horehound, anis hyssop, echinacea, Roman chamomile, or the Arizona native, chilitepene. From South Africa, society garlic has mild-tasting leaves that one can eat and still go out in society, or try garlic chives. Some landscape herbs are easily damaged by cold and should be planted in a protected place, including lemon grass, lemon verbena, caper, hoya santa, and mint marigold. You could keep these in pots on a sheltered porch. If you plant lavender, use varieties from hotter countries, French or Spanish, not English.
There is so much more to tell about growing herbs, it would take a book! One good for Tucson is "Herbs: Growing and Using the Plants of Romance," available at local nurseries or from Ironwood Press. For more ideas on landscaping with herbs, visit the Tucson Botanical Gardens. Moms get in free on Mother's Day!
Jacqueline A. Soule is a botanist and the director of Tierra del Sol Institute. She offers herb classes and on-site landscape design help and consulting. For more information please call 292-0504.