When a cilantro plant begins to flower, it is undergoing a natural process called bolting, which signals the end of its leaf-producing life cycle. This process is typically triggered by rising temperatures and longer daylight hours, causing the plant to shift focus from foliage production to reproduction. The plant’s dual identity becomes clear at this stage, as the flowers are the precursors to what will become the spice coriander. This transition presents a choice for the gardener: manage the flavor change, harvest the seeds, or prepare the garden for new plantings.
The Impact of Flowering on Cilantro Flavor
The moment the plant bolts, sending up a tall, rigid stalk, the chemical composition of the leaves begins to change dramatically. The plant diverts its energy and resources away from producing the fresh, grassy volatile compounds that give cilantro its characteristic flavor. This change results in a significant reduction in desirable compounds like decanal, which contribute to the fresh aroma.
Instead, the plant increases its concentration of other compounds, such as E-2-decenal and dodecanal, which are often described as having a soapy or acrid taste. While the leaves are still safe to consume, their flavor becomes notably less palatable, often turning bitter or pungent. The mature, lower leaves are generally the most affected by this flavor shift.
Some of the smaller, upper leaves near the developing flowers may still be worth harvesting for immediate culinary use, as they may retain a milder flavor profile. The tender stems can also be used, but the distinctive fragrance associated with fresh cilantro will be lost. For those who still wish to use the leaves, harvesting them immediately before the flowers fully open may slightly mitigate the change in taste.
Harvesting and Using Coriander Seeds
The flowering stage opens the door to a completely new product: the spice known as coriander. The delicate white or pale pink flowers, appearing in clusters called umbels, quickly fade to form small, round, green seed pods. These pods are the immature seeds, and they can be harvested fresh to be used in certain recipes, offering a bright, citrusy, and slightly spicy flavor.
For the more traditional dried coriander spice, the pods must be allowed to fully mature and dry on the plant. This process is complete when the green seeds turn a light brown or tan color, becoming firm and dry to the touch, which usually takes several weeks after flowering. The stems should then be cut a few inches below the seed heads.
To ensure a clean harvest, the cut stems can be placed upside down inside a brown paper bag, with the bag tied loosely around the stem to catch the falling seeds. The bag should be hung in a cool, dry, and well-ventilated area until the seeds completely release from the stalks. Once fully dry, the seeds can be stored whole in an airtight container for long-term use.
Post-Flowering Plant Management
After the plant has bolted and the seeds have been collected or have fallen, the gardener has a few options for the remaining physical structure. Cutting the stalks down to the base may prompt the plant to produce a few small, final leaves, but it will not revert to its former bushy, leaf-producing state. Cilantro is an annual, and once the bolting process is complete, its life cycle is essentially finished.
A common approach is to remove the entire spent plant from the garden bed, roots and all, and prepare the soil for a new crop. This is the most practical choice if you wish to immediately plant another herb or vegetable in the same spot. Alternatively, the plant can be left in place to fully mature and drop its seeds naturally.
Allowing the seeds to fall to the ground results in “volunteer” cilantro, which means new plants will sprout when the conditions, particularly the soil temperature, are favorable again. While this can lead to a continuous, if sporadic, supply of cilantro, it is a less controlled method of gardening. To delay future bolting, subsequent plantings should be given afternoon shade and consistently cool, moist soil.