Rhubarb is a long-lived perennial vegetable, often established in gardens by planting divisions known as crowns. Starting this plant from seed, however, is a cost-effective and rewarding alternative, though it requires patience. This method allows for the cultivation of many plants from a small initial investment. While the resulting plants may exhibit some natural variation, they will still produce the tart stalks. Successfully growing rhubarb from seed involves careful timing of the indoor start, precise sowing techniques, and diligent care of the young plants during their first year.
Optimal Timing and Material Preparation
The best time to start rhubarb seeds indoors is approximately eight to ten weeks before your area’s last expected frost date. This timing provides the seedlings with a sufficient head start to develop strong root systems before they are transplanted outside. Rhubarb seeds do not typically require cold stratification, but soaking them in warm water for a few hours before planting can help speed up germination.
Gathering the right materials is the first step toward successful germination. You will need high-quality rhubarb seeds, small pots or seed-starting trays, and a sterile seed-starting mix. The sterile mix prevents early fungal diseases like damping-off, which can quickly destroy tender seedlings. A heating mat can be beneficial, as rhubarb seeds germinate best when the soil temperature remains between 68°F and 74°F.
Step-by-Step Seed Sowing Procedure
Begin the sowing process by filling your chosen containers with the pre-moistened seed-starting mix, gently tamping the surface to create a level bed. Plant two seeds per small pot or cell to ensure at least one viable seedling per container. The seeds should be planted shallowly, covered with about one-quarter to one-half inch of the soil mix.
After sowing and lightly covering the seeds, mist the surface with water or use a bottom-watering technique by placing the trays in a shallow pan of water to avoid disturbing the newly planted seeds. The containers should be placed in a warm environment, ideally on a heating mat, to maintain the optimal soil temperature. Covering the tray with a clear plastic dome helps to maintain the high humidity. Rhubarb seeds typically sprout within seven to fourteen days under these controlled conditions.
Care of Seedlings and Field Establishment
Once the seedlings emerge, remove any plastic coverings and ensure they receive adequate light, which may require placing them under grow lights or on a very bright windowsill. If both seeds in a pot germinate, thin them by snipping the weaker seedling at the soil line, leaving the strongest plant to grow without root competition. This thinning process directs the plant’s energy into developing a robust crown.
As the seedlings grow, keep the soil consistently moist, but avoid overwatering. Introduce a diluted, balanced liquid fertilizer only after the first set of true leaves has fully developed. Before transplanting the young plants, they must undergo a hardening off period to prevent shock. This process involves gradually exposing them to outdoor conditions—direct sun, wind, and cooler temperatures—over a period of about a week.
Transplant the rhubarb seedlings into their permanent garden location in late spring or early summer after all danger of frost has passed. Rhubarb requires a site with well-drained, fertile soil, enriched with aged compost or manure, and should be spaced generously, three to four feet apart, to accommodate its mature size. Resist the temptation to harvest any stalks during the entire first year of growth. Allowing the plant to focus all its energy on establishing a deep, strong root system will ensure a productive, long-lasting perennial rhubarb patch.