The herb Coriandrum sativum is an annual plant prized for its intense, fresh flavor and dual utility. This single specimen yields two distinct culinary products: the fragrant leaves, known as cilantro, and the dried seeds, called coriander. This guide details how to successfully establish and maintain this versatile herb from seed in an outdoor garden environment.
Selecting the Site and Timing
Cilantro thrives as a cool-weather crop, performing best when daytime temperatures range between 50 and 85 degrees Fahrenheit. Planting should occur in early spring, just after the last expected frost, or in late summer or early fall. Sowing during these windows allows the plant to mature before the intense heat of summer arrives.
The location significantly influences the plant’s growth. While cilantro tolerates full sun during cooler periods, it benefits greatly from partial shade, especially in the afternoon once the weather warms. Positioning plants away from the hottest midday rays helps delay the natural tendency of the herb to flower and set seed prematurely.
Preparing the Soil and Sowing Seeds
Successful cilantro growth requires creating an optimal environment beneath the surface. The soil must be loose and well-draining, as this herb is highly susceptible to root rot in waterlogged conditions. Incorporating aged compost or other organic matter into the top six to eight inches of the planting bed improves both fertility and drainage.
Seeds should be sown directly into the ground, as Coriandrum sativum does not transplant well. Place seeds at a shallow depth of about one-quarter to one-half inch and gently cover them with soil. For continuous leaf production, employ successive planting by sowing a small batch of seeds every two to three weeks until the weather becomes too warm.
Proper spacing prevents overcrowding and allows for adequate air circulation. If planting in rows, space rows 12 to 15 inches apart. Individual plants should ultimately be spaced approximately six inches apart, though closer initial sowing followed by thinning is common to ensure a good stand.
Ongoing Care and Bolting Prevention
Consistent moisture is paramount to maintaining healthy cilantro plants and delaying flowering. The soil should remain evenly moist but never saturated, requiring regular watering, especially during dry spells. Allowing the soil to completely dry out stresses the plant and triggers premature seed production, known as bolting.
After seedlings emerge, thinning is necessary for robust growth. Overcrowded plants compete intensely for resources, accelerating the bolting process. Thin the seedlings so the remaining plants are spaced about six to eight inches apart, allowing each plant sufficient room to develop fully.
Managing heat stress is the most effective way to extend the harvest. When temperatures consistently rise above 75 degrees Fahrenheit, the plant naturally shifts its energy toward reproduction. Applying a two-to-three-inch layer of organic mulch helps insulate the soil and keep the roots cooler. Providing temporary shade, such as a shade cloth during the hottest part of the afternoon, can also significantly delay bolting and prolong the availability of fresh leaves.
Harvesting Cilantro and Coriander
Harvesting the leaves, or cilantro, should begin once the plant reaches six inches in height. To encourage continued growth, cut the outer stalks and leaves near the base of the plant, leaving the central growing point intact. Never remove more than one-third of the plant at any single time, allowing the remaining foliage to continue photosynthesis.
If the goal is to collect the seeds, known as coriander, allow the plant to bolt and produce small white or pink flowers. After flowering, the seeds will mature over several weeks, turning from green to brown. Harvest the seed heads just before the seeds fully dry and drop, cutting the entire stalk and placing it in a paper bag to catch any seeds that shatter.