The plant Coriandrum sativum serves a dual purpose in the kitchen, offering the fresh leaves known as cilantro and the dried seed spice called coriander. This single species is a cool-season annual herb that completes its life cycle relatively quickly. The common question for home gardeners is whether the dried, whole coriander seeds found in the spice aisle can be used to grow the leafy herb. The answer is yes, because the seeds are the reproductive unit of the plant, but success depends on understanding their unique biological structure.
Yes, But Seed Structure Matters
Dried coriander spice seeds retain their viability for planting, often for several years, as they are mature fruits harvested from the plant. Unlike most seeds, the round, tan-colored object purchased as a spice is a schizocarp, a dried fruit designed to split. This fruit contains two true seeds, known as mericarps, encased within a tough husk. The two seeds inside are half-spheres, creating the sphere shape of the fruit.
The hard outer husk acts as a natural barrier to water penetration and can inhibit germination if planted whole. Planting the intact spice fruit significantly lowers the chances of both mericarps germinating and delays the sprouting time. Understanding this dual-seed structure is the first step toward a successful harvest.
Mandatory Pre-Planting Preparation
To maximize the germination rate, the protective husk must be addressed before planting. The most effective method involves lightly crushing the dried fruit to separate it into its two mericarps. This requires gentle pressure, often achieved by rolling the seeds under a heavy object like a rolling pin.
Splitting the fruit exposes the individual seeds and helps break the dormancy enforced by the hard casing. After separation, the seeds benefit from a water soak for 24 to 48 hours to encourage imbibition, the absorption of water needed to begin germination. Planting the separated, pre-soaked mericarps results in a much faster and more reliable emergence of seedlings.
Sowing the Prepared Seeds
Coriander grows best in cooler weather and should be sown directly outdoors in early spring or fall, as it dislikes root disturbance from transplanting. Choose a location that receives full sun (at least six hours of direct light) or partial afternoon shade in warmer regions to prevent overheating. The ideal soil should be well-draining, loose, and amended with organic matter to promote strong taproot development.
Plant the prepared seeds shallowly, covering them with only about one-quarter to one-half inch of soil. Space the seeds roughly an inch apart, and then gently water the area to settle the soil. The optimal temperature range for germination is between 60 and 70 degrees Fahrenheit, where sprouts should emerge within seven to 14 days. Once the seedlings appear, they require consistent moisture but should never be allowed to sit in soggy conditions.
Ongoing Care and Harvesting
Once the seedlings have developed their first set of true leaves, they should be thinned to a final spacing of six to eight inches apart for maximum leaf production. Thinning ensures that each plant receives adequate light and air circulation, preventing dense growth that can encourage disease. Consistent and moderate watering is necessary to prevent the plant from becoming stressed, which is the primary trigger for premature flowering.
The biggest challenge is bolting, the rapid production of a flower stalk that occurs when temperatures rise above 75 degrees Fahrenheit. Once bolting begins, the leaf flavor becomes bitter as the plant focuses energy on seed production. To delay this, maintain cool, moist soil with mulch and provide afternoon shade during hot spells.
Harvesting the leaves, or cilantro, should begin when the outer leaves are large enough to use, cutting the foliage about an inch above the soil line. This “cut-and-come-again” method encourages the plant to produce more leaves, extending the harvest period. If the goal is to produce new coriander spice, allow the plant to bolt, flower, and set seed. The seeds are ready to harvest when the flower heads dry and turn brown, at which point they can be collected and dried thoroughly for storage or replanting.