The herb culantro (Eryngium foetidum) is a flavorful addition to many Caribbean and Asian cuisines. While its distinctive, long, serrated leaves are highly sought after, culantro seeds have specific requirements that often result in germination failure. Unlike quick-sprouting cilantro, successful cultivation requires overcoming the seed’s natural dormancy and providing the perfect microclimate.
Preparing the Planting Environment
Successful germination requires selecting the correct growing medium and timing. Start seeds indoors approximately six to eight weeks before the last expected frost date, as this tropical herb requires a long, warm season. The container must offer excellent drainage, as culantro thrives in consistently moist, yet never soggy, conditions.
Use a high-quality, sterile seed starting mix that is light and well-aerated. The medium should be slightly acidic to neutral, ideally with a pH range between 6.0 and 7.5. The delicate seeds and emerging roots benefit from the fine texture and sterility of a specialized mix, and the environment must provide sustained warmth.
Sowing the Seeds
The physical process of sowing culantro seeds is highly specialized because the seeds exhibit a trait known as photo-dormancy, meaning they require light to break dormancy and sprout. These tiny seeds should be scattered thinly across the surface of the pre-moistened seed starting mix. After scattering, gently press the seeds onto the soil surface to ensure good contact, but resist the urge to cover them with a layer of soil.
If you choose to use a covering, use only a very thin dusting, no more than one-eighth of an inch, of fine vermiculite, which allows light to penetrate while helping to maintain surface moisture. Initial watering should be done carefully to prevent the seeds from being displaced or washed away. Misting the surface with a spray bottle or, preferably, using a bottom-watering technique helps to saturate the soil evenly without disrupting the shallowly placed seeds.
Ensuring Successful Germination
Providing precise environmental controls is the most significant factor for encouraging culantro seeds to sprout. The requirement for germination is high, sustained heat, with the soil temperature needing to remain consistently between 75°F and 85°F. Maintaining this temperature range necessitates the use of a thermostatically controlled heat mat placed beneath the planting tray.
Consistent moisture and high ambient humidity are also necessary to transition the seed from dormancy. Immediately after sowing, cover the tray with a clear plastic humidity dome or plastic wrap to trap moisture and create a mini-greenhouse environment. The seeds require bright light immediately, so place the tray under grow lights or in a very bright location while maintaining heat and humidity. Germination is a slow process, often taking between 14 to 28 days, requiring strict maintenance of these tropical conditions until the first sprouts appear.
Initial Care of Young Seedlings
Once the culantro seedlings have emerged, they require careful attention as they develop their first true leaves. The primary challenge is transitioning the young plants from the high-humidity environment without causing shock. After the majority of seeds have sprouted, gradually remove the humidity dome over a few days to allow the seedlings to adjust to lower ambient humidity.
As the seedlings grow, they must be thinned to allow sufficient space for the characteristic rosette of leaves to develop. Space the remaining plants six to twelve inches apart to encourage robust growth. If started indoors, the plants must undergo “hardening off” before transplanting outside by gradually exposing them to increasing periods of outdoor sun and wind. Continue to keep the soil moist, watering when the top inch feels dry, but avoid overwatering.