Vegetable · Polygonaceae
Rhubarb
Rheum rhabarbarum
Plant it once and rhubarb keeps giving back for years, with tart red stalks every spring and big leaves you just leave be.
Full sun
Every 5–10 days
365–730 days
USDA 3–8
Overview
Rhubarb is that oddball vegetable that mostly ends up in dessert. Its tart red and green stalks cook down into pies, crumbles, and jam, which is how it got the nickname pie plant in the first place. It's part of the knotweed family, and it laughs off cold that would flatten most crops, taking winters all the way down to -40°F (-40°C).
Here's the thing about rhubarb: it likes to take its time. Pop a crown in the ground and it settles in as a long-lived perennial, throwing up fresh stalks every spring for a decade or more before it needs splitting. You'll skip the harvest that first year and take just a little the second, but from the third year on it gives back more than you'll know what to do with.
One thing you can't forget? You eat the stalks, not the leaves. Those big leaf blades are loaded with oxalic acid and they're toxic to people and pets, so they get cut off and tossed. Get that habit down and honestly, rhubarb is about as easy as growing gets.
Care
The short version: rhubarb wants full sun, deep and fertile soil, and steady moisture, roughly an inch of water a week. Feed it in early spring when the crown wakes up, mulch it to keep things cool, and split the crown every few years so the stalks keep coming in strong.
Light
Rhubarb really wants full sun for the best stalks, though it'll put up with partial shade where summers get warm. The more light it gets, the thicker and more generous the crop, so give it a bright spot if you can.
Water
Keep the soil evenly moist but not waterlogged, which works out to about an inch (2.5 cm) of water a week. Water deeper through hot, dry spells, and toss a thick organic mulch on top to hold the moisture and keep the crown cool.
Soil
Give rhubarb deep, fertile, well-drained loam that's full of organic matter. A pH between 6.0 and 6.8 is what it likes, and drainage really matters, because a crown sitting in wet soil will just rot.
Temperature
Cold? No problem. Rhubarb handles anything from -40°F to 86°F (-40°C to 30°C). It actually needs a real winter chill to go dormant and bounce back strong, so it tends to struggle where summers stay hot.
Humidity
There's no humidity number to sweat here; the usual 40% to 60% outdoors is plenty. What matters more is air moving around those big leaves, since crowded, damp foliage is what brings on leaf spot.
Feeding
Feed rhubarb once in early spring, right as the crown wakes up, with a balanced fertilizer or well-composted manure. It's a hungry plant, so rich soil plus that yearly spring feeding is what keeps the stalks nice and thick.
Pruning
As soon as a central flower stalk pops up, cut it off at the base, or the plant pours all its energy into seed instead of stalks. Pull off any dead, yellowing, or frost-damaged leaves too, and always bin the toxic blades rather than feed them to animals.
Repotting
Rhubarb stays put in the ground, but the crown needs splitting every 5 to 10 years to keep its go. Thin, spindly stalks or a clump dying out in the middle? That's your sign to lift it, split it, and replant the strong bits.
Size & spacing
A grown plant hits about 2 to 4 feet (60 to 120 cm) tall and spreads just as wide, so give each crown 3 to 4 feet (90 to 120 cm) to itself. Those big leaves need the room for air to move and for the plant to fill out.
When to plant
Rhubarb runs on the cold, so there's no need to hurry. Set dormant crowns out in early spring as soon as the soil's workable, then leave the plant alone that first year while it gets its roots down. Stalks show up from spring into early summer, and by the third year you can harvest all you want.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Sow: start seed indoors 8-10 weeks before the last spring frost (seed-grown plants are slow and variable)
- Plant: set out dormant crowns in early spring as soon as the soil can be worked (fall planting also works in mild areas)
- Harvest: harvest stalks in spring through early summer; do not harvest the first year, take only a few stalks the second year, and harvest fully from the third year onward
Hardiness
USDA hardiness zones: 3–8
Temperature: down to -40°C
Troubleshooting
Rhubarb's a tough customer, and most of its problems come back to a crowded crown, soggy soil, or a hot summer. Learn to read the stalks and leaves and you'll catch trouble early, while it's still easy to fix. Find what matches below, then sort it out before it sets the plant back.
A soft brown crown and a plant flopping over
When the crown goes soft, brown, and mushy and the whole plant flops, that's crown rot, usually from wet feet in slow-draining soil, sometimes with a fungus like Phytophthora in the mix. There's no saving a rotted crown, so dig it up and get rid of it. Replant healthy divisions somewhere raised and well-drained, and don't pile mulch right up against the crown.
Fix:
- Remove and destroy affected crowns
- Improve drainage and replant healthy divisions on a raised, well-drained site
A tall flower stalk popping up from the middle
That tall stalk with the creamy flowers on top? That's bolting, rhubarb's attempt to set seed when summer heats up or the crown gets old and crowded. It steals energy the stalks need, so cut it off at the base the second you spot it. Keep the plant watered and mulched, and split those tired old crowns to keep it from happening again next year.
Fix:
- Cut the flower stalk off at its base as soon as it is seen
- Keep plants consistently watered and mulched
Stalks coming in thin, short, and weak
Skinny stalks are almost always an overcrowded crown that's run out of room, though poor soil and too much harvesting don't help. Lift and split the crown in early spring, replant the strongest pieces, and feed with compost or a nitrogen-rich fertilizer. Then go easy on the harvest for a season so the plant can bounce back.
Fix:
- Divide the crown in early spring and replant vigorous pieces
- Top-dress with compost or a nitrogen-rich fertilizer
- Reduce or stop harvesting for a season to let the plant recover
Spots or chewed holes on the big leaves
Round tan-to-purple spots usually mean a fungal leaf spot like Ascochyta or Ramularia, while ragged holes are slugs or the rhubarb curculio at work. Pull the worst leaves and get rid of them, open the planting up for better airflow, and water at the base. Hand-pick any beetles and stay on top of the slugs, and it'll shake it off.
Fix:
- Remove and destroy badly affected leaves
- Improve air circulation and avoid overhead watering
- Hand-pick beetles and manage slugs
Toxicity
Rhubarb splits neatly into safe and not-safe, so it pays to know which is which. The cooked stalks are good eating, but those big leaf blades carry oxalic acid and anthraquinone glycosides that are toxic to people, cats, dogs, horses, and livestock. Cut the leaves off, throw them somewhere no animal can get to them, and never hand trimmings to a pet or grazing stock.
Toxic to
Cats · Dogs · Horses · Rabbits · Livestock · Birds
Safe for
People
Cats Moderate
A cat that nibbles a leaf blade usually starts drooling and pawing at its mouth, then throws up and goes all sluggish. A big mouthful's worse, since the oxalates can bring on tremors and put a strain on its kidneys.
Dogs Moderate
A dog that chews the foliage will probably drool, get an upset stomach, go off its food, and just want to lie around. Let it eat enough and those same crystals can trigger tremors and kidney damage.
Horses Moderate
The blades irritate a horse's mouth and set off heavy drooling, colic-like cramping, and weakness. A big feed risks lasting kidney harm, so it's best to fence horses away from the foliage.
Rabbits Toxic
The oxalic acid in the leaves is genuinely dangerous for rabbits, and there's just no safe amount. Keep the blades and trimmings totally out of reach.
Livestock Toxic
Cattle, sheep, and goats that graze the leaves can get severe oxalate poisoning, with drooling, gut pain, staggering, and kidney failure. Don't ever toss leaf trimmings into a pasture or pen.
Birds Toxic
That same oxalic acid and those anthraquinone compounds make the leaves unsafe for poultry and pet birds alike. Don't let the backyard hens scratch through blades you've thrown out.
People Stalks safe
Cooked rhubarb stalks are a kitchen classic and totally safe to eat, but the leaf blades aren't. They've got oxalic acid that brings on a burning mouth, nausea, and vomiting, so trim the leaves off and throw them out.
The red or green leaf STALKS (petioles) are safe to eat when cooked, but the large LEAF BLADES are toxic to pets and people and must never be eaten or fed to animals. Cut blades off and dispose of them; do not leave trimmed leaves where pets or livestock can reach them.
Helpline numbers
United States
ASPCA Animal Poison Control: (888) 426-4435 (fee applies)
United Kingdom
Animal PoisonLine: 01202 509000 (fee applies)
Australia
Animal Poisons Helpline: 1300 869 738
Varieties
Only a few rhubarb cultivars turn up in most gardens, and they mostly differ in color, sweetness, and how tough they are. These are the ones worth knowing by name.
Victoria
Victoria's a vigorous old heirloom with green stalks that blush pink at the base, and it's the one cultivar folks usually grow from seed.
Canada Red
Canada Red keeps its deep red color all the way up the stalk, and it's sweeter and less stringy than most.
MacDonald
MacDonald gives you tender, bright red stalks plus good resistance to root rot, which makes it the one to pick for heavier soils.
Glaskins Perpetual
Glaskins Perpetual has less oxalic acid, so you can keep picking later into the season than with other kinds.
How to propagate
The easiest way to get more rhubarb? Just split an established crown. You can grow it from seed too, if you don't mind a longer wait and a bit of a surprise.
DivisionEasy
Early spring while the crown is dormant (fall is also possible) · 1-2 years before light harvest, with full harvest by the third year
Splitting a crown is the surest way to get more rhubarb, and it's easy. Lift a dormant crown in early spring, cut it into pieces that each have one or two strong buds and a good chunk of root, and replant them with the buds sitting just at or below the soil line. Give each one a year or two before a light pick, with a full harvest by the third year. Best part? Every division comes up true to its parent.
SeedModerate
Start indoors 8-10 weeks before the last spring frost, then transplant out · 2-3 years to a full harvest
You can grow rhubarb from seed, but it's slow and a bit of a gamble. Sow indoors 8 to 10 weeks before your last spring frost, transplant them out, and figure on 2 to 3 years before a full harvest. Seedlings vary and won't come true to a named cultivar, so save seed for when you're feeling adventurous and stick with division for varieties you know.
Myths
The whole rhubarb plant is poisonous, so you can't eat any of it.
Nope, only the leaf blades are toxic, thanks to oxalic acid and soluble calcium oxalates. The cooked stalks are safe, everyday food that's filled pies and crumbles for generations. Just cut the blades off, bin them, and enjoy the stalks.
Rhubarb stalks turn poisonous once it flowers or after a hot summer.
Flowering and heat don't touch the stalks at all. The poison's only ever in the leaf blades, never the stalks, so a bolting plant is still fine to harvest. Just snap off the flower stalk and keep the crop coming.