Cilantro (Coriandrum sativum) is a popular cool-season annual herb valued for both its fresh leaves and its dried seeds, known as coriander. Unlike many herbs that thrive in summer heat, cilantro has a short lifespan. Successful cultivation depends almost entirely on precise timing, as the plant reacts strongly to rising temperatures and increasing daylight hours. This sensitivity means the primary challenge is scheduling the planting to maximize the leafy harvest before the plant completes its life cycle.
Optimal Timing for Spring Sowing
The initial spring planting takes advantage of the brief window between the last hard frost and the arrival of summer heat. Cilantro performs best when air and soil temperatures remain consistently between 50°F and 75°F. Seeds should be sown directly into the garden bed, as cilantro develops a taproot and does not transplant well.
The first sowing should occur two to four weeks before the average last expected frost date in your region. Sow seeds about one-quarter to one-half inch deep as soon as the soil is workable. This early start capitalizes on the short days of early spring, which helps delay the plant’s transition into flowering.
Maintaining Supply with Succession Planting
Because a single cilantro plant produces leaves for only a short period, a continuous harvest requires succession planting. This technique involves sowing small batches of seeds at regular intervals rather than planting the entire crop at once. Planting new seeds every two to three weeks, starting immediately after the initial spring sowing, ensures that fresh, leafy plants are always maturing.
This staggered schedule provides a rolling supply of tender leaves before older plants start to bolt. Continue succession sowing until the ambient daily temperature consistently reaches the upper limit of the plant’s tolerance. Once temperatures regularly exceed 75°F, new sowings will bolt too quickly to provide a worthwhile harvest.
Understanding Heat Stress and Bolting
The cilantro harvest window is limited by the plant’s tendency to “bolt,” the premature shift from vegetative to reproductive growth. Bolting is triggered by two environmental signals: consistently high temperatures (above 75°F to 80°F) and the long daylight hours of late spring and early summer.
Once these conditions are met, the plant rapidly sends up a tall, rigid flower stalk, signaling the end of the leafy harvest. The leaves on a bolted plant change from the familiar broad, flat shape to a narrower, feathery texture, and their flavor becomes less desirable. Providing afternoon shade as the season warms can help mitigate high temperatures and slightly delay the process.
Maximizing Yield with Fall Planting
The fall planting season often offers the most successful and prolonged cilantro harvest. Unlike spring, autumn features cooling temperatures and shortening daylight hours. These conditions naturally inhibit bolting, allowing the plant to remain in its desirable leafy stage for an extended period.
To maximize the fall yield, sow seeds six to eight weeks before the first expected hard frost date in your area. This timing allows the plants to reach a harvestable size before freezing temperatures arrive. Cilantro can tolerate light frost, permitting a lengthy, productive harvest that often surpasses the short window available in the spring.