Cilantro, or Coriandrum sativum, is a dual-purpose plant cherished for both its fresh leaves and its dried seeds, known as coriander. A common frustration for home gardeners is “bolting,” the plant’s natural, genetically programmed shift from producing leafy growth to reproductive growth. This process is primarily triggered by warming temperatures and increasing daylight hours, signaling the plant to quickly produce flowers and seeds to ensure the next generation.
The Immediate Impact of Flowering on Cilantro Leaves
Once the cilantro plant initiates the bolting process by sending up a thick central stalk, the quality of the leaves changes significantly. The plant diverts energy from leaf production toward the development of the flower stalk and subsequent seeds. This redirection immediately impacts the plant’s culinary value.
The taste of the leaves changes due to a shift in the concentration of volatile compounds. As the plant bolts, the leaves often develop a noticeably bitter or even a soapy taste, making them far less desirable for fresh use. Furthermore, the leaf structure itself transforms from broad, flat foliage to a delicate, lacy, and fern-like appearance.
The stems also become woody and tough as the plant prepares to support the weight of the developing seed heads. While the bolted leaves are technically safe to consume, the harsh flavor and fibrous texture mean that fresh harvesting for culinary purposes is generally no longer recommended. At this point, the gardener’s focus should shift to the future seed harvest.
Harvesting and Using Coriander Seeds
The appearance of flowers signals that the plant is transitioning to its second valuable product: coriander seeds. The small, white or pale pink flowers attract pollinators, and once fertilized, they develop into spherical, green seed pods. These immature green seeds offer a distinctive, bright citrus-herb flavor and can be harvested and used fresh, though they must be consumed quickly.
For the dried spice, you must allow the seeds to mature fully on the plant. The seed pods will gradually turn from green to a light tan or brown color, and the entire stalk will begin to dry out. The time for harvest is when most of the seeds have browned but before they dry completely and shatter, scattering the seed onto the ground.
To harvest, cut the entire stalk just a few inches below the seed heads. The simplest method for drying is to place the cut stems upside down inside a brown paper bag, tying the bag closed around the stems. Hang this setup in a cool, dry, and well-ventilated area for a couple of weeks. As the seeds dry, they will fall neatly into the bottom of the bag. Once fully dry and separated from the chaff, store the coriander seeds whole in an airtight container, as grinding them immediately causes them to lose flavor much faster.
Strategies to Delay Bolting
While bolting is a natural part of the cilantro life cycle, several cultural practices can delay the switch from leaf production to flowering. Since high temperatures are the primary trigger, planting cilantro during the cooler shoulder seasons of early spring and late summer is the most effective approach. The ideal temperature range for leaf production is generally below 75 degrees Fahrenheit.
Providing afternoon shade can help regulate soil and plant temperature during warmer periods. Planting cilantro near taller crops or using a shade cloth during the hottest part of the day prevents the heat stress that causes premature bolting. Consistent moisture is also important, as drought stress will prompt the plant to produce seeds as a survival mechanism.
Gardeners can also practice succession planting by sowing a new, small batch of seeds every two to three weeks. This ensures that even when one planting inevitably bolts, a younger crop is coming along to provide a continuous supply of fresh leaves. Selecting varieties that are specifically bred to be slow-bolting, such as ‘Calypso’ or ‘Caribe,’ can also extend the leaf harvest window.