Cilantro, a popular herb known for its bright, fresh flavor, is a cool-season annual. Gardeners frequently encounter “bolting,” the plant’s rapid shift from producing flavorful leaves to developing flowers and seeds. This natural process cuts the leaf harvest short and makes the remaining foliage less desirable for cooking. While bolting cannot be stopped entirely, adapting your harvesting methods allows you to salvage the remaining leaves and gain a valuable secondary harvest: the spice coriander.
Understanding the Bolting Process
Bolting is a survival mechanism initiated when cilantro perceives environmental stress, primarily heat and the long days of summer. This process marks the plant’s transition from vegetative growth (leaves) to reproductive growth (flowers and seeds). The first sign is an abrupt elongation of the central stem, which shoots upward. As the plant dedicates energy to this new growth, the leaves change shape, becoming more delicate and fern-like near the top. The primary triggers are soil temperatures consistently rising above 75°F and increasing daylight hours.
Salvaging Remaining Cilantro Leaves
Once a flower stalk emerges, the flavor profile of the remaining foliage changes, often becoming more bitter or “soapy.” Despite this flavor shift, the lower, broader leaves can still be harvested immediately before the quality declines. Focus harvesting efforts on the outer leaves, as they retain more of their original flavor than the smaller, newly formed leaves near the top.
To utilize this final leaf harvest, chop the leaves and use them right away, or preserve them for later use. Freezing the fresh leaves in ice cube trays with water or oil locks in their flavor for use in sauces, soups, or stews. This technique is helpful because the leaves’ strong flavor can be blended in prepared dishes, making any slight bitterness less apparent.
Transitioning to Coriander Seed Production
Allowing the bolted plant to complete its reproductive cycle provides a secondary harvest: coriander, the spice made from the dried seeds. After the plant flowers, small, green, round seed pods form where the blooms once were. These seeds mature over several weeks, gradually drying and turning a light brown or tan color.
The ideal time to harvest is when the majority of the seeds are brown and dry, but before the seed heads shatter. To collect them, cut the entire stalk near the base of the plant. Tie the stalks in small bundles and hang them upside down in a cool, dark, dry area for one to two weeks.
Hanging the bundles inside a paper bag catches any seeds that fall off during drying. Once dried, the seeds are easily stripped from the stems by gently rubbing the heads. The collected seeds can be stored whole in an airtight container, providing a spice with a warm, lemony aroma distinctly different from the fresh leaves.
Strategies for Preventing Premature Bolting
While bolting is inevitable, several practices can significantly delay the process, extending fresh leaf production. Cilantro is a cool-season crop, thriving in temperatures between 50°F and 70°F, so plant it in early spring and late summer. Consistent planting, known as succession planting, involves sowing small batches of seeds every two to three weeks.
Providing afternoon shade is an effective strategy for shielding plants from intense heat. Maintaining consistent soil moisture is also necessary, as dry soil or irregular watering stresses the plant, forcing early reproduction.