Vegetable · Polygonaceae
Rhubarb
Rheum rhabarbarum
Give rhubarb a spot once and it rewards you for years, sending up tart red stalks each spring while those big leaves ask nothing of you but a little space.
Full sun
Every 5–10 days
365–730 days
USDA 3–8
Overview
Rhubarb is one of the friendliest crops you can plant, and it forgives the small mistakes every new gardener makes. Its tart red and green stalks cook down into pies, crumbles, and jam, which is exactly how it earned the homey old name pie plant. It sits in the knotweed family and laughs off cold that would finish most vegetables, coming through winters as low as -40°F (-40°C).
The main thing rhubarb asks for is a little patience, and that part is easy to give. Settle a crown into the ground and it becomes a long-lived perennial, pushing up fresh stalks every spring for a decade or more before it wants dividing. You let it rest that first year and take just a little the second, and by the third year it hands back more than you can use.
There is really just one rule to keep in mind, and it is simple to follow: eat the stalks and leave the leaves. Those big leaf blades carry oxalic acid and are toxic to both people and animals, so you cut them off and toss them out. Get comfortable with that single habit and you will find rhubarb about as forgiving as gardening gets.
Care
The short version: give rhubarb full sun, deep and fertile soil, and steady moisture at roughly an inch of water a week, and it will settle right in. Feed it in early spring as the crown wakes up, tuck a mulch around it to keep things cool, and lift and divide the crown every few years so the stalks keep coming strong.
Light
Rhubarb does its best in full sun, though it will get by with partial shade where summers run warm. The more light it soaks up, the thicker and more generous the stalks come in, so pick a bright, open spot if you can.
Water
Aim to keep the soil evenly moist but never soggy, which comes to about an inch (2.5 cm) of water each week. Water more deeply through hot, dry stretches, and lay a thick organic mulch over the bed to hold that moisture in and keep the crown pleasantly cool.
Soil
Set rhubarb into deep, fertile, well-drained loam worked full of organic matter and it will thank you. A pH somewhere between 6.0 and 6.8 suits it nicely, and good drainage is the one thing it truly will not forgive, since a crown left sitting in wet soil rots.
Temperature
Cold is no worry here: rhubarb handles anything from -40°F to 86°F (-40°C to 30°C). It actually depends on a real winter chill to rest and return strong each spring, so it tends to sulk in places where the summers stay hot.
Humidity
Ordinary outdoor humidity in the 40% to 60% band is all rhubarb needs, so there is nothing to measure or worry over. What matters more is air moving freely around those big leaves, because crowded, damp foliage is what invites leaf spot.
Feeding
Feed rhubarb once in early spring, right as the crown breaks dormancy, using a balanced fertilizer or well-composted manure. It is a hungry plant, so rich soil paired with that yearly spring feeding is what keeps the stalks thick and worth picking.
Pruning
As soon as a central flower stalk appears, snip it off at the base, or the plant will spend its strength making seed instead of stalks. Tidy away any dead, yellowing, or frost-damaged leaves too, and always bin those toxic blades rather than offer them to animals.
Repotting
Rhubarb lives happily in the ground, but the crown wants dividing every 5 to 10 years to stay full of life. Thin, spindly stalks or a clump that is dying out in the middle are its way of asking you to lift it, split it, and replant the strongest pieces.
Size & spacing
A settled plant grows 2 to 4 feet (60 to 120 cm) tall and spreads about as far across, so leave each crown 3 to 4 feet (90 to 120 cm) of elbow room. Those broad leaves need space for air to move and for the plant to stretch out and fill in.
When to plant
Rhubarb takes its cue from the cold, so there is no rush. Set dormant crowns out in early spring the moment the soil is workable, then let the plant keep that first year to itself while its roots settle in. Stalks arrive from spring into early summer, and by the third year you can harvest with a free hand.
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 is a sturdy, forgiving plant, and most of its troubles trace back to a crowded crown or ground that stays too wet, with a spell of summer heat sometimes adding to it. Learn to read what the stalks and leaves are telling you and you can step in early, while the fix is still simple. Find the symptom that matches below, then act before the plant loses ground.
A soft, browning crown and a plant that is caving in
When the crown turns soft, brown, and mushy and the whole plant slumps, that is crown rot, usually from wet feet in soil that drains too slowly and sometimes from a soil fungus like Phytophthora. A rotted crown cannot be saved, so dig it out and get rid of it, hard as that feels. Replant healthy divisions on a raised, free-draining spot, and keep mulch from ever piling right 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 rising from the middle of the plant
That tall stalk topped with creamy blooms is bolting, the plant trying to set seed when summer heats up or the crown grows old and crowded. It pulls energy away from the stalks you want, so cut it off at the base as soon as you notice it, and there is no harm done. Keep the plant watered and mulched, and divide worn old crowns to head this off next year.
Fix:
- Cut the flower stalk off at its base as soon as it is seen
- Keep plants consistently watered and mulched
Stalks pushing up thin, short, and feeble
Weak, skinny stalks nearly always come down to an overcrowded crown that has outgrown its patch, with thin soil and too much harvesting piling on. Lift and divide the crown in early spring, settle the strongest pieces back in, and feed with compost or a nitrogen-rich fertilizer. Then go easy on the picking for a season and give the plant room to rebuild.
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 across the big leaf blades
Round tan-to-purple spots on the leaves point to a fungal leaf spot such as Ascochyta or Ramularia, while ragged holes are the handiwork of slugs or the rhubarb curculio. Strip off the worst-hit leaves and destroy them, open the planting up so air moves through, and water at the base instead of overhead. Hand-pick any beetles you find and keep after the slugs, and the plant shrugs it off.
Fix:
- Remove and destroy badly affected leaves
- Improve air circulation and avoid overhead watering
- Hand-pick beetles and manage slugs
Toxicity
Rhubarb draws a clean line between what is safe and what is not, and it helps to know that line well. The cooked stalks are genuinely good food, but the big leaf blades hold oxalic acid and anthraquinone glycosides that are toxic to people, cats, dogs, horses, and livestock. Cut the leaves off, throw them where no animal can get at them, and never pass trimmings to a pet or grazing stock.
Toxic to
Cats · Dogs · Horses · Rabbits · Livestock · Birds
Safe for
People
Cats Moderate
If a cat nibbles a leaf blade, it usually begins drooling and pawing at its mouth before it vomits and goes quiet and tired. A bigger mouthful is the real worry, since the oxalates can bring on tremors and put a strain on the kidneys.
Dogs Moderate
A dog that chews the foliage tends to drool, get an upset stomach, go off its food, and just want to rest. Eat enough of it and those same crystals can set off tremors and harm the kidneys.
Horses Moderate
The blades sting a horse's mouth and start up heavy drooling, colic-like cramping, and weakness. A large feed risks lasting kidney harm, so it is kindest to fence horses well away from the foliage.
Rabbits Toxic
The oxalic acid in the leaves is truly dangerous to rabbits, and there is no amount that counts as safe. Keep every blade and trimming completely out of their reach.
Livestock Toxic
Cattle, sheep, and goats that graze the leaves can end up with severe oxalate poisoning, showing drooling, gut pain, staggering, and kidney failure. Never toss leaf trimmings into a pasture or pen where they might find them.
Birds Toxic
The same oxalic acid and anthraquinone compounds make the leaves unsafe for both poultry and pet birds. Do not let backyard hens scratch through blades you have thrown out.
People Stalks safe
Cooked rhubarb stalks are a beloved kitchen staple and safe to enjoy, but the leaf blades are not. They hold oxalic acid that brings a burning mouth, nausea, and vomiting, so trim the leaves off and throw them away.
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 show up in most gardens, and they differ mostly in color, sweetness, and how well they stand up over time. These are the ones worth getting to know before you plant.
Victoria
Victoria is a vigorous old heirloom with green stalks that blush pink near the base, and it is the one cultivar most gardeners raise from seed.
Canada Red
Canada Red holds its deep red color the whole length of the stalk and tends to taste sweeter and less stringy than most.
MacDonald
MacDonald offers tender, bright red stalks along with solid resistance to root rot, which makes it the friendly choice for heavier soils.
Glaskins Perpetual
Glaskins Perpetual carries less oxalic acid, which lets you keep picking later into the season than other kinds allow.
How to propagate
The easy, dependable way to get more rhubarb is to split an established crown, and it is well within reach for a first-timer. You can also raise it from seed if you do not mind waiting a while and letting the results surprise you a little.
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
Division is the surest, most beginner-friendly way to make more rhubarb. Lift a dormant crown in early spring and cut it into pieces, each holding one or two strong buds and a good chunk of root, then replant them with the buds sitting just at or below the soil line. Let each new piece grow for a year or two before you take a light picking, with a full harvest by the third year. Best of all, 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
Growing rhubarb from seed is possible, though it asks for patience and a bit of luck. Sow indoors 8 to 10 weeks before your last spring frost, move the seedlings outside, and count on 2 to 3 years before a full harvest. Because seedlings vary and will not come true to a named cultivar, save seed-growing for a fun experiment and lean on division when you want a variety you know.
Myths
The entire rhubarb plant is poisonous and no part of it is safe to eat.
Only the leaf blades are toxic, thanks to oxalic acid and soluble calcium oxalates. The cooked stalks are safe, everyday food, the kind that has filled pies and crumbles for generations. Trim the blades away, drop them in the bin, and enjoy the stalks with a clear conscience.
Rhubarb stalks turn poisonous once the plant flowers or after a hot spell.
Neither flowering nor a hot summer changes the stalks one bit. The toxin lives only in the leaf blades, never in the stalks, so a plant that has bolted is still perfectly good to pick. Just snap the flower stalk off and the harvest carries right on.