How to Grow Rhubarb: Planting, Spacing, Care & Harvest
Quick answer
Plant dormant crowns 4 to 6 weeks before last spring frost (Purdue). Illinois sets the crown bud 2 inches below the surface; UMN sets bare-root crowns level with the soil — show both. Eat stalks only; leaves are toxic. No harvest year 1 from crowns.
Rhubarb at a glance
Weeks relative to last frost (LF). Colored weeks show when our ZIP planner schedules each step.
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Planting dates for your ZIP: the ZIP planting planner counts each window from your local frost dates.
Organic pests and diseases: see also organic pest control. Use any product as the label directs.
Toxicity: Leaves (and roots per NC State) are poisonous. Eat cooked petioles (stalks) only. After a severe freeze, Illinois says do not eat the leafstalks.
Planting timing
Purdue HO-186: hardy — “plant 4-6 weeks before last spring frost.” (Purdue Extension) Matches planner Plant crowns last frost −6 to −4. Illinois: “Plant or divide rhubarb roots in early spring while the plants are dormant.” Seed start indoors “six weeks before the last frost date”; germination may take up to two weeks. Direct seeding in the garden “not recommended except in extreme southern areas.” (Illinois Extension) UMN: seed indoors “six weeks before the last frost date”; harden ≥1 week; plant out at the same depth as the pot; bare-root crowns with the crown just level with the soil. Hardy USDA Zone 4; worth trying in Zone 3 (MN framing). (UMN Extension) Site permanently at the garden edge — productive for years (Illinois: five years or more; UMN 15+ years with care).
Depth and spacing
Illinois: plant roots with “crown bud 2 inches below the surface”; space roots 36 to 48 inches apart in rows 3 to 4 feet apart. Raised beds help prevent crown rot. UMN: give each plant a three-foot-by-three-foot area; full-day sun; prepare soil at least two feet deep; add compost/composted manure; let soil settle before planting so plants are not set too deep. The crown-depth sources conflict (Illinois 2 in below vs UMN level with soil), so we show both. Division: Illinois cut old roots into four to eight pieces with at least one strong bud; renew after ≥5 years of full harvest. UMN divide early season with a clean sharp shovel (half or thirds) or dig and knife-divide.
Sun, soil and water
Sun: UMN all-day sun. Illinois garden site with good drainage. Soil: UMN well-drained; loam better than sand; pH “not important” for MN garden soils. Illinois: work plenty of well-rotted manure or compost into the bed before planting; raised beds where drainage is poor. Water: UMN soak to at least one inch depth each week in the growing season. Illinois irrigate during extended dry periods; organic mulch helps unless drainage is poor. Weeds: UMN frequent shallow cultivation year 1–2; keep the tool away from the crown. Illinois cultivate shallowly as needed.
Care
Heavy feeder (UMN): annual compost and/or balanced fertilizer in spring; Illinois complete fertilizer before spring growth and high-nitrogen side-dress late June — prefer compost language; avoid phosphorus buildup (UMN). Seed stalks: cut off as soon as they appear (UMN; Illinois) so energy stays in the crown. Winter / mulch: Illinois manure or compost late fall/early winter — “Do not cover the crowns.”
Harvest, toxicity and storage
Toxicity: edible part is petioles (stalks) only. Leaves are toxic (oxalic acid) — UMN; Illinois; NC State medium poison severity for leaves and roots. (NC State) Wait: UMN “Wait until the second season before harvesting. Wait until the third season if you started from seed.” Illinois: no harvest year 1; 1 or 2 weeks year 2; 8 to 10 weeks (full season) year 3+. Method: UMN hold stalk, pull and twist — do not cut with a knife (spreads disease; stub is an entry point). Immediately trim and discard leaf blades. Illinois: pull leafstalks; remove only about one-third of leaves from a plant at any one time. Season: UMN until end of June for full harvest; occasional later pulls OK (myth that the whole plant becomes toxic in summer is false — UMN); stalks may be tougher. Freeze damage: Illinois — after a severe freeze, do not eat leafstalks. Storage: Illinois trim leaves; refrigerate unwashed, wrapped, up to three weeks.
Pests and diseases (organic)
Rhubarb curculio: Illinois: snout beetle bores into stalks, crowns, roots; also attacks wild dock (Rumex). “Destroy all wild dock growing around the garden.” Burn badly infected parts in July after egg lay. UMN: dark snouted beetle about ½ to ¾ inch long; remove nearby grassy weeds and curly dock (normal host). Insect pests “generally not a problem.”
Stalk borers: UMN: similar damage; cultural weed host removal.
Crown / root rot and leaf spots: Illinois: raised beds help prevent crown rotting. UMN: sunny well-drained site; in wet years fungi invade — restart in a new spot if crowns rot. Leaf spots Ascochyta rhei and Ramularia rhei: selective harvest of infected stalks; remove and destroy all leaves after first hard frost. Viruses: remove plant and start over.
Related: ZIP planner · organic pest control
Frequently asked questions
When do I plant rhubarb?
Purdue: 4–6 weeks before last spring frost while dormant. Illinois: early spring dormant planting.
Are the leaves safe?
No. Leaves (and roots per NC State) are toxic. Eat cooked stalks only (UMN; Illinois; NC State).
When can I harvest?
No harvest year 1 from crowns; light year 2; full season year 3+ (Illinois; UMN). Pull-and-twist; never leave leaf blades on harvested stalks.
Why are stalks small and full of seed stalks?
Illinois: crowding, old plants, or low fertility — divide, give space, improve organic matter.
More grow guides: Asparagus · Peas · Cauliflower · Leeks · Parsley · Swiss chard · Radishes · Eggplant · Arugula · Cilantro · All grow guides
Sources
- Purdue University: Purdue Extension
- University of Illinois Extension: Rhubarb
- University of Minnesota Extension: UMN Extension
- NC State Extension: Rheum rhabarbarum