CORVALLIS - If you plant cilantro now, in late June or early July, it will flower, or bolt prematurely during the long, hot days of summer. You'll lose the cilantro leaves, but gain coriander seeds.
Both temperature and day length influence flowering and seed setting, according to Jim Myers, vegetable breeder at Oregon State University's horticulture department.
In warm or hot weather, cilantro has a shorter life cycle. In mid-summer, cilantro will bolt into small lacy flowers, then set seeds in about four to six weeks from time of sowing. In the cooler shorter days of spring or fall, cilantro will grow for several weeks to months longer before flowering and setting seed.
To prolong the time until bolting, plant cilantro seed in a cooler part of the garden, suggests Ross Penhallegon, horticulturist with the OSU Extension Service. Or plant it in early spring and again in late summer when days are shorter and temperatures are lower.
Bolting has a benefit. The flowers transform into seeds that can be collected, dried and ground into the spice coriander. Cilantro flowers are great for attracting beneficial insects to your garden, especially in the early morning and late evening.
Gardeners should plant successive batches of seed to ensure fresh cilantro throughout the growing season. Avoid planting in mid-summer, as plants will soon bolt before growing much.
Remember, if you want cilantro leaves, plant them in a cool or semi-shaded area in the heat of the season. Cilantro is most successfully grown by direct seeding or from starts. But be careful, as the long roots make it difficult to transplant.
Sow cilantro seeds directly into sunny, fertile beds from early spring through early summer and then again in early autumn. Plant 10 to 15 seeds per foot of row. Cover the seeds with about one-half inch of soil. Thin plants to eight inches apart with rows 18 to 24 inches apart. Seeds will germinate with soil temperatures of 55 to 68 degrees. Cilantro plants can withstand temperatures down to freezing.
Commonly used in Latin American, Asian and other cuisine, cilantro has become a popular herb in the United States. Its piquant flavor is a favorite in salsas, Thai food, garnishes and in stir-fries.
All parts of the plant are useful. The seeds of the cilantro or coriander plant are ground and used as the spice called coriander, popular in breads, spice cakes, pickling spices and in Asian foods. Coriander root is used in Thai dishes.
Cilantro leaves are best used fresh, as they lose much of their flavor when dried. The small immature leaves have the most flavor. Seeds, used as coriander, should be harvested before they drop. The roots, also used in Thai and Vietnamese cooking, are best harvested in the autumn.