Cilantro (Coriandrum sativum) is a popular culinary herb, known for its distinct, bright flavor in dishes ranging from salsas to curries. Gardeners often debate whether it is a cultivated herb or a persistent garden nuisance. This confusion stems from cilantro’s vigorous growth habit, which causes it to spread rapidly and appear unexpectedly. Understanding its botanical nature clarifies why this desirable plant sometimes behaves like an unwanted guest.
The Botanical Definition of a Weed
The term “weed” does not represent a formal scientific classification, but rather a subjective, context-dependent label. Botanically, a plant is defined by its species, genus, and family, such as Coriandrum sativum. Formal classification does not determine desirability or purpose.
In practical horticulture, a weed is simply a plant growing where it is not desired; a gardener’s decision defines the term. For example, a rose bush growing in a vegetable patch could be considered a weed. This context-based understanding means a plant can be a cultivated crop in one location and an unwelcome volunteer in another, while maintaining the same biological identity.
Cilantro’s Status as a Cultivated Herb
Cilantro is a cultivated annual herb belonging to the Apiaceae family (carrot or parsley). It is grown for two products: the fresh leaves (cilantro) and the dried seeds (coriander). Its life cycle progresses from leaf production to flowering, a process known as bolting.
Bolting is triggered by rising temperatures and lengthening daylight hours, signaling the plant must reproduce. When cilantro bolts, it rapidly sends up a flower stalk, and the initial broad leaves are replaced by finer, lacy foliage. The small white or pale pink flowers then develop into viable seeds.
The volume of seeds produced by a single plant, combined with its annual life cycle, is the mechanism behind its “weedy” behavior. If mature coriander seeds drop onto the soil, they easily germinate the following season, resulting in volunteer plants. This prolific self-seeding is a survival strategy that creates an aggressive, unwanted spread from a gardener’s perspective.
Managing Aggressive Self-Seeding
Gardeners can manage cilantro’s aggressive tendency to self-seed through several preventative methods. One effective strategy is succession planting, which involves sowing new seeds every two to three weeks. This ensures a continuous supply of fresh, non-bolting leaves while staggering the plants’ reproductive cycles.
Preventing seed production is the most direct control measure. Gardeners can deadhead the plant by cutting the flower stalks back as soon as they appear, which prevents the development of seeds. Allowing some plants to bolt, however, can be beneficial, as the flowers attract beneficial insects like syrphid flies and parasitic wasps.
If the goal is to harvest coriander seeds, they must be collected promptly before they scatter. The seeds are ready to harvest when the seed heads turn a straw color, at which point they can be dried and threshed. For the volunteer seedlings that do appear, they can be easily thinned out early in the season, either by hand-pulling them or by transplanting them to a desired location, though cilantro does not transplant well due to its taproot.