Newberg, Oregon—The annual conference of the International Herb Growers and Marketers Association (IHGMA) was held in Washington State in July, and it gave me the opportunity to compare notes with fellow herb growers from across the nation.
I feel fortunate to live in a climate that is so temperate and accommodating to growing herbs. Winters in the Northeast are so hard that growers must take all of their rosemaries inside for the winter. I leave all of my upright rosemaries planted outside, although the prostrate or creeping varieties, which are less hardy, do have to go into the greenhouse. (The creeping cultivar Rosmarinus ‘Severn Sea’ has surprised me the past four winters by surviving outside, even through an entire week when the temperature reached 3°F.)
Southern growers, on the other hand, have such hot, humid summers that they must constantly battle fungal diseases such as powdery mildew when growing lavenders and rosemaries. The only plant that’s sure to get powdery mildew in our area is bee balm (Monarda didyma), and most growers just accept it and try to minimize it by good sanitation and by avoiding watering late in the afternoon.
California growers often boast that they can grow everything outside year round, but they have no really distinct seasons nor severe cold winter temperatures—nor even snow! Without a cold period to make them go dormant, herbs such as French tarragon (Artemisa dracunculus var. sativa) can’t get the rest period they need to recuperate in preparation for another season of growth. That’s why Californians often substitute Mexican mint marigold (Tagetes lucida) in their cooking: it doesn’t need a dormant period.
Californians miss the splendid fall colors that herbs can produce as cold weather approaches. Color intensity increases in the blue of Jackman’s Blue or Blue Mound rue (Ruta graveolens), the crisp golds of golden sage (Salvia officinalis ‘Icterina’), and the smoldering reds of tricolor sage (S. o. ‘Tricolor’), whose edges turn even deeper red later in the season until they approach the rich burgundies of purple sage (S. o. ‘Purpurascens’). Shorter day lengths and colder temperatures seem to heighten the foliage contrast of the smaller, more subtly variegated herbs. Creeping lemon thyme (Thymus citriodorus ‘Doone Valley’), Mayfair thyme (T. c. ‘Mayfair’), and the upright golden and silver lemon thymes (T. c. ‘Aureus’ and ‘Argenteus’) are at their best now. The silver portion of silver thyme’s leaf margins will redden subtly as temperatures drop toward frost levels. All these thymes make excellent culinary wreaths, and the colors will hold up for the holidays.
I can feel clearly the temperature transition from summer to fall. I wake up on each crisp, cold morning to find the air clearer and the colors of the herb garden more intense than the day before. I appreciate more the warmth of the sun on my back, and I have more layers of clothes to shed as the day goes on. I notice that the gold stripe down the midrib of each leaf of English Wedgewood thyme (T. ‘English Wedgewood’), which in the earlier summer heat faded into the darker green background, is now more prominent, and I make plans to propagate it from cuttings of the most variegated portions of the plant.
I am already anticipating next spring when I can sow seeds I collected earlier this month from a variegated angelica that self-sowed in my garden two years ago. I’m eager to learn whether the seed will be true to its variegated parent. Like so many other biennials, the parent plant will soon die now that it has gone to seed, and this seed will be its only legacy.