Rhubarb

Rhubarb (Rheum rhabarbarum) is one of the few crops where planting it is better described as an investment than a garden project. You won’t harvest the first year. You’ll harvest lightly the second year. From year three onward, a healthy crown requires almost no input and produces 3–6 lb of stalks annually for 20 years or longer without replanting. The math on that per-season cost is essentially zero.

What rhubarb actually is

Rhubarb is a perennial vegetable classified and sold as a fruit. Only the stalks are edible - the leaves contain high concentrations of oxalic acid and are toxic. This is not a minor caveat: rhubarb leaf consumption has caused poisoning and fatalities. Discard leaves in a compost pile or trash, never on the ground where livestock or children might access them.

The stalk color - red, pink, or green - varies by cultivar and has no bearing on ripeness or flavor. ‘Victoria’ is a green-stalked cultivar that predates most red types and is highly productive. ‘Canada Red,’ ‘Crimson Red,’ and ‘Valentine’ are red-stalked cultivars marketed for appearance. Red-stalked types are popular for fresh sale but taste essentially the same as green (University of Minnesota Extension, Rhubarb in the Garden, 2021).

Rhubarb requires a dormancy period with temperatures below 40°F to break dormancy properly and produce vigorously. This makes it genuinely suited to Zones 3–7 but problematic in Zones 8 and warmer, where insufficient winter chill leads to poor spring regrowth. It is not a warm-climate crop.

The ROI case

A crown at a garden center costs $6–$12. One crown, well-established, yields 3–6 lb per season starting in year three (Cornell Cooperative Extension, Rhubarb, 2020). At $2.50–$4.00/lb retail (USDA AMS, 2023), that’s $7.50–$24 annually from a single crown. After the initial planting cost is recouped in years three to four, every subsequent harvest is pure return.

Crown division adds to the math. Every 4–5 years, a rhubarb crown should be divided to maintain vigor. Each division becomes a new producing crown. A single plant becomes two, then four. After 10 years of division, a gardener who started with one $10 crown has a permanent rhubarb planting worth several hundred dollars in transplant value, generating free divisions indefinitely.

Growing requirements

Plant crowns in early spring when soil can be worked, or in fall in mild climates. Set the crown bud (the growing point) 2 inches below soil surface. Planted too deep, crowns rot; too shallow, they dry out and heave during freeze-thaw cycles.

Space 3–4 feet between crowns in all directions. Rhubarb grows large - mature plants reach 3 feet across with substantial root systems. Crowding stresses plants and reduces yield.

Rhubarb is not particular about soil but performs best in well-drained, fertile loam at pH 6.0–6.8. Waterlogged soil causes crown rot. Amend beds with 3–4 inches of compost before planting. Top-dress each crown with compost in early spring annually.

Remove flower stalks immediately when they appear. Flowering redirects energy from leaf and stalk production. A crown that is allowed to go to seed exhausts itself and yields poorly for the rest of the season. Snap the flower stalk off at the base as soon as you spot it.

Year one and two management

Year one: do not harvest anything. The crown needs to establish a root system. If you harvest stalks in year one, you weaken the plant and set back the timeline for productive harvests.

Year two: harvest no more than one-third of the stalks. Take the larger, outer stalks and leave the smaller central ones to continue feeding the crown.

Year three and beyond: harvest freely through the spring season, stopping when stalk diameter decreases noticeably (a sign the plant is tired). Stop harvesting by midsummer to allow the plant to rebuild energy reserves for next year.

What goes wrong

Crown rot (Phytophthora spp., also Rhizoctonia spp.) causes crowns to turn brown and mushy, usually as a result of waterlogged soil or planting too deep. No effective treatment; remove affected crowns. Replant in improved drainage.

Rhubarb curculio (Lixus concavus) is a rust-colored snout beetle that bores into rhubarb stalks, crowns, and roots, leaving characteristic frass-filled tunnels. Infested stalks wilt and yellow. Hand-pick adults in early summer. Remove dock (Rumex spp.) weeds from the vicinity - the beetle’s primary host plant.

Leaf spot (Ramularia rhei) produces small, water-soaked spots on leaves that expand and turn reddish-brown with pale centers. It’s rarely serious enough to impact the harvest. Remove heavily infected foliage.

Frost damage to emerging stalks in early spring is common and usually not serious. Damaged stalks turn dark and mushy; cut them off and the plant will produce more. A hard freeze on newly emerged crowns can kill them back, but established roots typically resprout without permanent damage.

Harvest and storage

Harvest rhubarb stalks by grasping near the base and pulling with a slight twist - the stalk should snap cleanly from the crown. Don’t cut with a knife unless necessary; cutting leaves a stub that may rot and introduce disease.

Stalks should be firm and crisp. Flaccid or pithy stalks are overmature or dehydrated; they’re edible but texture and flavor suffer. Target stalks that are 12–18 inches long for maximum yield per harvest.

Trim leaves immediately and compost or discard them. Stalks keep refrigerated for 2–3 weeks in a bag. For longer storage, chop and freeze raw without blanching; frozen rhubarb works well in pies, jams, and sauces.

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Related crops: Strawberry, Garlic

Related reading: First Three Years ROI - how to calculate the full lifecycle return on a perennial planting