Cilantro (Coriandrum sativum) is a popular annual herb often perceived as a weed due to its sudden appearance in garden beds. Cilantro does spread, but not in the invasive manner of many perennial herbs. It does not use underground runners or creeping stems to colonize new areas. Instead, its spread depends entirely on its reproductive cycle, propagating efficiently through the natural dispersal of its seeds, commonly known as coriander. This process of self-seeding results in what gardeners call “volunteer” plants.
Understanding Cilantro’s Physical Growth Habit
Cilantro is a short-lived annual plant that develops a single taproot, which defines its growth habit and limits its physical spread. This deep, sensitive root structure anchors the plant and makes it poorly suited for transplanting once established. The plant initially forms a rosette of broad, flat leaves, growing in a clump that does not expand horizontally beneath the soil.
Unlike aggressive spreaders such as mint, cilantro lacks underground stems (rhizomes) or above-ground runners (stolons) used for vegetative propagation. Its growth focuses on producing a dense cluster of leaves before a single, tall flowering stalk emerges. Any new cilantro appearing away from the parent plant must have originated from a seed, confirming its movement is seed-based, not root-based.
The Mechanism of Cilantro Self-Seeding
The mechanism of cilantro’s spread is linked to its rapid transition from vegetative growth to seed production, a process called bolting. This shift is triggered by rising temperatures (often above 75°F to 80°F) and increasing daylight hours during late spring and early summer. Once bolting begins, the central stalk elongates, developing delicate, lace-like foliage distinct from the original rosette leaves.
The plant produces umbels—umbrella-shaped clusters of small, white to pinkish flowers—at the top of this stalk. These flowers are soon replaced by small, round, green fruits containing the seeds (coriander). As the seeds mature, they turn beige or brown and dry out on the plant. When fully ripened, the seed heads naturally shatter, dropping the heavy, round seeds directly onto the soil. The seeds often remain dormant through the summer heat, waiting for the cool, moist conditions of late fall or early spring to germinate, resulting in a fresh patch of volunteer cilantro.
Managing Volunteer Cilantro Plants
The presence of volunteer cilantro plants can be managed through control or utilization. To control the spread, the most effective method is preventing the parent plant from completing its reproductive cycle. This involves removing the flower stalks—a process called deadheading—as soon as they appear, cutting them off before the seeds ripen and dry.
If seeds have already dropped, light, shallow cultivation of the soil surface helps. Disturbing the top layer exposes seeds to air and sun, which reduces their viability and prevents successful germination. Conversely, gardeners can use self-seeding for continuous harvests, known as succession planting. Allowing a few plants to go to seed ensures new volunteer seedlings appear naturally, which should then be thinned to a spacing of three to six inches.