The choice of whether to let your cilantro plant flower, a process known as bolting, depends entirely on your desired harvest. Cilantro (Coriandrum sativum) provides two distinct culinary products: the leaves (cilantro) and the dried seeds (coriander). Bolting is a natural biological transition where the plant shifts its energy from vegetative growth (leafy greens) to reproductive growth (flowers and seeds). This change creates a dilemma because maximizing leaf quality and producing seeds are mutually exclusive goals.
How Bolting Changes Cilantro Leaf Quality
Allowing the plant to flower fundamentally alters the quality of the leaves, making them less desirable for culinary use. Once bolting initiates, the plant rapidly develops a thick, elongated central stem that shoots upward. This structural change signals a metabolic shift, causing the plant to stop focusing on generating the broad, flat leaves valued as an herb.
The foliage that remains or grows after bolting changes dramatically in both texture and flavor. Leaves become noticeably tougher and develop a thinner, lacier, and more fern-like appearance compared to the original flat, parsley-like leaves. The flavor profile changes, often becoming significantly more bitter or acquiring a soapy taste that many people find unpalatable.
This flavor alteration is a result of the plant’s reproductive stage, and cutting off the flower stalk will not reverse the change in the existing leaves. The plant pulls nutrients from the lower foliage to fuel the development of the flowers and seeds. This process further diminishes the leaves’ vibrant color and fresh taste, marking the end of the line for fresh leaf harvest from that plant.
The Purpose of Flowering: Harvesting Coriander Seeds
If your goal shifts from harvesting fresh foliage to collecting the spice, allowing the cilantro to flower becomes the correct choice. The plant first produces delicate, lacy white or pale pink flowers in umbrella-shaped clusters, which attract beneficial insects. These flowers quickly transition into small, round seed pods, which are known as coriander.
The seeds are initially bright green and can be harvested at this immature stage for a sharper, more pungent flavor. Coriander is most commonly collected when the seeds reach full maturity, typically two to three weeks after the flowers have faded. The seeds are ready for a dry harvest when the entire seed head begins to turn light brown and dry out.
To harvest the dried spice, cut the stems a few inches below the seed heads before the seeds drop naturally. Place the cut stems upside down in a paper bag, tying the bag shut around the stems. Hang them in a cool, dry, and well-ventilated area for a couple of weeks; as the seeds fully dry, they will fall into the bottom of the bag. This provides a fresh supply of coriander for cooking or planting next season.
Controlling Bolting and Making the Decision
Cilantro is a cool-season annual that bolts primarily in response to environmental stress, specifically high temperatures and longer daylight hours. Temperatures consistently above 70°F (21°C) and the increasing day length of late spring and early summer are the main triggers for rushing seed production. Irregular watering and dry soil conditions also stress the plant, encouraging premature bolting.
To delay bolting and maximize leaf harvest, you can employ a few gardening techniques. Planting cilantro in a location that receives partial afternoon shade helps keep the plant cooler during the hottest part of the day. Consistent soil moisture is essential, as is regular harvesting, which encourages the plant to focus its energy on producing new foliage.
The final decision rests on your priorities. If you want a continuous supply of fresh leaves, plant in succession every few weeks and pull the plants as soon as the central stalk begins to form. If you value the spice, allow a few plants to fully bolt and set seed for a harvest of home-grown coriander.