How to Grow Rhubarb from Seed: The Complete Beginner's Guide
You can grow rhubarb (Rheum × hybridum) from seed by soaking it for 2 to 3 hours, sowing it 1 to 2 cm deep indoors from February to April at 15 to 20°C, and planting young plants out 75 to 90 cm apart after the last frost. Don't pull any stalks in the first year, take a light harvest in the second, and harvest fully from the third year, from April to June. Only the stalks are edible: rhubarb leaves are toxic.
Short on time? Seed-grown rhubarb takes three years to crop fully and varies in stalk colour. Our young rhubarb plants get you picking a year or two sooner.
Few perennial vegetables reward patience quite like rhubarb (Rheum Ă— hybridum). Plant it once in a sunny corner of the garden and, with almost no fuss, it will hand you armfuls of tart, ruby-pink stalks every spring for a decade or more. It shrugs off Irish weather, copes with neglect, and asks for very little beyond a rich patch of soil and an occasional feed of compost.
Most people buy rhubarb as a "crown" (a dormant root division), but growing it from seed is far cheaper if you want several plants, and it's a satisfying way to raise a patch from scratch. The one trade-off: seed-grown rhubarb doesn't always come perfectly true to its parent, so stalk colour can vary from deep red to green-blushed-pink. The flavour and vigour, though, are every bit as good.
This guide walks you through sowing rhubarb seed, raising strong young plants, and establishing a bed that will feed you for years, plus how to avoid the single most important safety mistake beginners make with this plant.
Rhubarb Quick Facts
Latin name: Rheum Ă— hybridum
Difficulty: Easy once established
Sow: February to April (indoors) or April to May (direct)
Position: Full sun to light shade
Soil: Deep, fertile, well-drained, enriched with compost
Time to first harvest: Do not harvest in year one; light harvest in year two; full harvest from year three
Plant lifespan: 10 to 20 years with division every 5 to 6 years
Step 1: Sowing Rhubarb Seed
Rhubarb seed germinates readily with a little warmth, making it a forgiving plant for beginners to start indoors.
Soak seeds in warm water for 2 to 3 hours before sowing to soften the outer casing and speed germination.
Sow around 1 to 2 cm deep in trays or small pots filled with a peat-free seed compost, one or two seeds per module.
Keep at a steady 15 to 20°C on a bright windowsill or in a propagator; germination usually takes 14 to 21 days.
Step 2: Caring for Seedlings
Once seedlings appear, the goal is steady, unchecked growth rather than speed.
Thin to the strongest seedling per module once true leaves appear, snipping rather than pulling the weaker one to avoid disturbing roots.
Keep compost consistently moist but never waterlogged, and turn pots regularly so seedlings grow upright rather than leaning toward the light.
Begin a weak, diluted organic liquid feed every couple of weeks once plants have three or four true leaves.
Step 3: Hardening Off and Planting Out
Rhubarb is fully hardy once established, but young plants still need a gentle transition outdoors.
Harden off over 10 to 14 days in late spring, once the last frost has passed, gradually increasing time outside each day.
Choose a sunny, open bed with deep, fertile, well-draining soil; dig in plenty of well-rotted manure or compost the season before if you can.
Plant with the crown sitting just at soil level, spacing plants at least 75 to 90 cm apart in each direction. Rhubarb leaves get enormous, and good airflow prevents fungal problems.
Step 4: First-Year Care
The most important rule with seed-grown rhubarb is also the hardest to follow: leave it alone.
Do not harvest any stalks in the plant's first year, no matter how tempting it looks. This lets the crown build the root reserves it needs for years of future cropping.
Water deeply during dry spells, especially through the first summer while roots are still establishing.
Remove any flower stalks that appear by cutting them right at the base, as flowering diverts energy away from the crown.
Step 5: Ongoing Care
Feeding: Top-dress generously with well-rotted manure or compost each autumn or early spring. Rhubarb is a hungry feeder and rewards rich soil with thicker stalks.
Mulching: Apply a thick organic mulch around (not on top of) the crown each spring to suppress weeds and lock in moisture.
Watering: Water well during dry spells, particularly while stalks are actively growing in spring and early summer.
Dividing: Every 5 to 6 years, lift and divide congested crowns in late autumn or early spring, replanting one strong division per new position to keep plants vigorous.
Forcing: For an earlier, extra-tender crop, cover the crown with a bucket or terracotta forcing pot in late winter to exclude light. This produces pale, sweet stalks a few weeks ahead of schedule.
Step 6: Harvesting and Using Your Crop
From year two, take a light harvest of just a few stalks; from year three onward, harvest more freely over an 8 to 10 week window from April to June.
Pull stalks with a firm twist close to the base rather than cutting, which helps prevent rot at the crown.
Never harvest more than a third of the visible stalks at once, and stop harvesting by midsummer to let the plant recover and store energy for next year.
Important safety note: Rhubarb stalks are delicious and safe to eat, but the leaves contain high levels of oxalic acid and are toxic if eaten in quantity. Always trim leaves off and compost them separately rather than eating them.
Troubleshooting
Thin, weak stalks: Usually a sign of poor soil fertility or overcrowding. Feed generously and divide congested crowns.
Crown rot: Often caused by waterlogged soil or mulch piled directly against the crown; improve drainage and keep mulch clear of the stem.
Plant keeps flowering: Common in older or stressed plants, especially during hot, dry spells; remove flower stalks promptly and keep the plant well watered and fed.
Slow to establish: Seed-grown rhubarb is naturally slower in its first year or two than a crown-grown plant. Be patient and resist the urge to harvest early.
FAQ: Growing Rhubarb from Seed
Can I really grow rhubarb from seed, or should I just buy a crown?
Seed works well and is much cheaper if you want several plants, though it takes an extra year to reach full cropping size compared with a crown. If you only want one or two plants and don't mind the cost, a crown will fruit sooner.
Why can't I eat rhubarb leaves?
Rhubarb leaves contain concentrated oxalic acid, which is toxic in quantity. The stalks themselves contain only trace amounts and are perfectly safe. Just trim and discard the leaves.
How do I know when to stop harvesting for the season?
As a rule of thumb, stop by midsummer (typically end of June/early July in Ireland) even if stalks look tempting, so the plant can rebuild its energy reserves for next spring.
Does rhubarb need a lot of space?
Yes, a mature plant can spread well over a metre wide, so give it room. It's a good candidate for the edge of a food forest or a dedicated perennial bed rather than a tight vegetable row.
A well-fed rhubarb crown is one of the lowest-maintenance, highest-reward plants you can grow. Plant it once, feed it well, and it will quietly outlive most other things in your garden while handing you the makings of crumbles and jams every spring.
Seed or Plant? Getting Your Rhubarb Patch Started
Growing rhubarb from seed is cheap if you want several plants, but it takes three years to crop fully and stalk colour varies. For a reliable patch sooner, starting with a young plant is the easier route.
At Earthling Plants we grow rhubarb as young potted plants, ready to go into rich, well-drained soil. Rhubarb is a hungry feeder, so a nearby patch of comfrey Bocking 14 makes an easy home-grown mulch and feed.
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