Start indoors or direct sow?

Start rhubarb indoors and transplant the seedlings, especially in cold-winter regions, to give plants a head start. It has a sturdy root system but establishes best when moved while young and handled gently.

When to start Rhubarb seeds

Sow indoors about 8 to 10 weeks before the average last spring frost. Transplant after frost danger has passed and soil is workable, or set plants out in early fall where summers are hot.

How to sow the seeds

Sow seeds 1/4 inch deep in a sterile seed-starting mix in 2- to 3-inch pots or deep cells. Use containers with drainage and keep them in a warm, bright location after sowing.

Germination

Rhubarb usually germinates in about 7 to 14 days, though it can take longer. Keep the mix evenly moist, not saturated, at roughly 65 to 75 F.

Seedling care

Give seedlings bright light for 14 to 16 hours daily under grow lights, placed close enough to prevent stretching. Water when the mix begins to dry at the surface, provide airflow, and thin to one strong seedling per pot.

Transplanting & hardening off

Harden seedlings off over 7 to 10 days before planting them in full sun to light shade and rich, well-drained soil. Set the crown at soil level, space plants about 3 to 4 feet apart, and water deeply after planting.

Tips

Do not harvest stalks during the first year, since the plant needs foliage to build a strong crown. Remove flower stalks if they form during establishment to direct energy into roots and leaves.

General seed-starting guidance for US home gardens; timing depends on your local frost dates and variety. Page updated Aug 4, 2026.