Growing rhubarb: cold-climate perennial vegetable
Rhubarb (*Rheum rhabarbarum*) is one of the few perennial vegetables in common cultivation, producing harvests from the same planting for 10–20 years. It is unusual in being classified as a vegetable while being used almost exclusively as a fruit in cooking. The leaf stalks (petioles) are the.
Rhubarb (Rheum rhabarbarum) is one of the few perennial vegetables in common cultivation, producing harvests from the same planting for 10–20 years. It is unusual in being classified as a vegetable while being used almost exclusively as a fruit in cooking. The leaf stalks (petioles) are the edible part; the leaves themselves are toxic due to high concentrations of oxalic acid.
Rhubarb is a cold-climate plant. Unlike most vegetables, it performs better in zone 3–5 than in zones 7–8, and is not practical south of zone 7.
Zones and cold requirements
Per Cornell Cooperative Extension, rhubarb requires freezing temperatures in winter for dormancy and subsequent vigorous spring growth. USDA zones 3–6 are ideal. In zone 7, rhubarb performs adequately but productivity decreases. Per NC State Extension, zones 8 and warmer are generally too warm for reliable rhubarb culture — the plant grows but produces poorly because the dormancy requirement is not fully met.
Planting crowns vs. seed
Per Penn State Extension, rhubarb is almost always started from crowns (divided root sections with dormant buds) rather than seed. Seed-grown rhubarb takes one additional year to reach harvestable size, and variety characteristics are not reliably preserved from seed.
Plant crowns in early spring when soil temperatures reach 40–50°F. Space crowns 3–4 feet apart; rhubarb plants expand to 3–4 feet diameter at maturity.
Planting depth and technique
Per Missouri Botanical Garden, plant rhubarb crowns so the buds are 1–2 inches below the soil surface. Deeper planting delays emergence; shallower planting exposes buds to frost. The crown should sit in a planting hole 12 inches deep filled with well-amended soil.
Per Penn State Extension, incorporate 3–4 inches of compost into the planting hole and bed. Rhubarb is a heavy feeder over its long life and benefits from generous organic matter at establishment.
Soil and fertility
Per Clemson HGIC, rhubarb prefers rich, well-drained, slightly acidic to neutral soil (pH 6.0–6.8). It does not tolerate waterlogged conditions and will develop crown rot in poor drainage.
Annual fertilization is important for a long-lived perennial bed. Per Penn State Extension, apply a balanced fertilizer (10-10-10) at 1.5 lbs per 10 feet of row in early spring as growth begins, and again after the harvest season ends. Side-dressing with compost in fall (2–3 inches over the crown area) is also beneficial.
The first two years: no harvest
Per Cornell Cooperative Extension, no stalks should be harvested in the first year after planting. In the second year, take a light harvest (3–4 stalks per plant) over 1–2 weeks only. Full harvest (8–10 stalks per plant over 4–6 weeks) begins in year 3.
This patience is essential. The crown must build substantial root mass before supporting repeated harvests. Premature heavy harvesting permanently reduces the productivity of the planting.
Harvest technique
Per Clemson HGIC, harvest stalks when they reach 12–18 inches long and 3/4 to 1 inch diameter. Grasp the stalk near the base and pull with a slight twist — it will detach cleanly. Alternatively, cut with a clean knife at the base.
Remove and discard the leaves immediately. Rhubarb leaves are toxic due to oxalic acid and anthraquinone glycosides. They should not be composted in beds where the compost will be applied to food plants (the compounds may persist). Per UC IPM, leaf toxicity is significant — ingestion of large quantities of rhubarb leaves can cause serious illness.
Removing flower stalks
Per Missouri Botanical Garden, rhubarb occasionally produces thick flower stalks topped with a plume of small white flowers. Allow these to develop only if you want seed for propagation experiments. For production purposes, remove flower stalks immediately when they appear — seed production diverts energy from petiole development and reduces yield.
Dividing established crowns
Per Rutgers NJAES, rhubarb crowns should be divided every 10–15 years when they become overcrowded and productivity declines. Divide in early spring before growth begins, or in early fall:
- Dig the entire crown with a spading fork
- Cut into sections, each with at least 2–3 healthy buds and a substantial root section
- Replant at original depth; allow new plantings to establish for 2 years before heavy harvest
Divisions from productive crowns are the most reliable starting material for new rhubarb beds.
Variety selection
Per Cornell Cooperative Extension and NC State Extension:
| Variety | Stalk Color | Notes |
|---|---|---|
| 'Victoria' | Green-red mottled | Traditional; reliable; widely available |
| 'Crimson Red' | Deep red | Good flavor; red color throughout |
| 'Canada Red' | Deep red | Cold-hardy; one of the redder varieties |
| 'Riverside Giant' | Green-red | Very vigorous; large plants |
| 'Holstein Bloodred' | Red | Reliable red color; good yields |
Per NC State Extension, stalk color ranges from predominantly green ('Victoria') to deep red ('Canada Red'). Green-stalked varieties typically produce more abundantly; red-stalked varieties have more visual appeal but similar flavor.
Common problems
| Symptom | Cause | Fix |
|---|---|---|
| Crown rot, collapse | Poor drainage; Phytophthora | Improve drainage; do not replant rhubarb in affected soil |
| Spindly stalks | Crown overcrowded; or insufficient sunlight | Divide crown; ensure 6+ hours sun |
| Poor production in warm climates | Insufficient cold dormancy | Accept limited production south of zone 6; or choose 'Victoria' which is slightly more heat-tolerant |
| Leaf spots | Ramularia leaf spot (fungal) | Usually cosmetic; remove severely affected leaves |
| Flower stalks appear | Normal; varietal tendency | Remove immediately to redirect energy |
Frequently asked questions
Can I eat the rhubarb leaves? No. Per Clemson HGIC, rhubarb leaves contain toxic concentrations of oxalic acid and anthraquinone compounds. Ingestion causes nausea, vomiting, and in large quantities can cause kidney failure. The leaves have no safe culinary use.
Why is my rhubarb producing thin, weak stalks? Per Penn State Extension, the most common causes are overcrowded crown, insufficient sun, or overharvesting in previous seasons. Divide if the planting is 10+ years old. Ensure 6–8 hours of sun. Limit harvest to 4–6 weeks and no more than one-third of the stalks per harvest.
Can I force rhubarb early indoors? Yes. Per Missouri Botanical Garden, lifting crowns in winter and potting them in a dark, cool space (50–60°F) forces early pale etiolated stalks in 3–5 weeks. This is a traditional British technique for producing tender, pale "champagne" rhubarb. The forced crowns are discarded or replanted after forcing — they need a rest period before they can be forced again.
What is the difference between rhubarb and chard? Per Cornell Cooperative Extension, rhubarb (Rheum rhabarbarum) and chard (Beta vulgaris subsp. cicla) both have wide stalks and large leaves, but are unrelated. Chard leaves are edible and nutritious; rhubarb leaves are toxic. Rhubarb is a perennial; chard is an annual. The two are easily distinguished by rhubarb's broad, triangular leaves and the sour flavor of its raw stalks.
Sources
- Cornell Cooperative Extension — Rhubarb Production
- Penn State Extension — Rhubarb
- Clemson HGIC — Rhubarb
- NC State Extension — Rhubarb Production
- Missouri Botanical Garden — Rheum rhabarbarum
- Rutgers NJAES — Rhubarb
- UC IPM — Rhubarb Leaf Toxicity