Growing Rhubarb: Planting, Harvesting and Dividing in Cold Climates
Rhubarb is the first thing to harvest in many northern gardens and one of the toughest plants you can grow. A single clump can produce for a decade or more with almost no attention. Get the first few years right and it will look after itself.
The short answer
- Plant crowns in spring, about 90 cm (3 ft) apart, with the buds 2.5 to 5 cm below the soil.
- Do not harvest for the first two seasons. In year three, pick for about four weeks; after that, for 8 to 10 weeks.
- Never take more than half the stalks from a plant at once.
- Snap off flower stalks as soon as they appear.
- Do not eat the leaves.
Guidance from Iowa State University Extension.
Varieties
- Red-stalked: Canada Red, Crimson Red, MacDonald, Valentine. Popular for colour and often sweeter.
- Green-stalked: Victoria. Very productive, though less showy in pies.
Rhubarb grown from a neighbour’s division is just as good, as long as the plant is healthy.
Where and how to plant
- Sun: 6 to 8 hours of direct sun. Avoid tree shade; it competes for light and water.
- Soil: rich and well drained. Work compost or well-rotted manure deep into heavy clay before planting.
- Spacing: about 90 cm between plants. Each clump gets big.
- Depth: set bare-root crowns with the buds 2.5 to 5 cm below the surface. Plant potted rhubarb at the depth it grew in the pot.
- Water thoroughly after planting, and deeply every 7 to 10 days in dry weather.
Choose the spot carefully: rhubarb is a long-term resident and dislikes being moved.
The first years
Leave new plants alone for two full seasons so the roots can build up. In the third year, harvest for about four weeks. From the fourth year on, you can pick for 8 to 10 weeks in spring and early summer.
How to harvest
- Pick stalks once they are 25 to 38 cm long.
- Grip a stalk near the base, pull up and twist slightly to one side. Do not cut; pulling cleanly reduces rot.
- Cut off the leaf right away and put it in the compost.
- Take no more than half of the fully grown stalks at a time.
In cold climates, the main harvest runs from late spring into early summer. Light summer picking is fine occasionally, but heavy summer harvests weaken next year’s crop.
Flower stalks
Thick, round stalks topped with a flower head take energy away from the leaves you want to eat. Snap them off at the base as soon as they appear.
The leaves are not food
Rhubarb leaves contain much more oxalic acid than the stalks and should not be eaten. They are safe to compost.
Frost
Rhubarb handles spring frost well. If a hard freeze turns stalks soft and mushy or blackens the leaves, pull and discard those stalks; new growth that comes up afterward is fine to eat. In fall, leave the foliage until a hard freeze kills it, since the leaves feed the roots for next year.
Feeding and dividing
- Feed in early spring before growth starts, keeping fertilizer off the crown. Mulch with 5 to 7.5 cm of compost or straw.
- When clumps get crowded and stalks thin, usually after 8 to 10 years, divide in early spring. Each division needs at least 2 to 3 buds and a good piece of root.
Keep reading
Frequently Asked Questions
When can I start harvesting rhubarb?
Do not harvest for the first two seasons. In the third year, pick for about four weeks; after that, for 8 to 10 weeks.
How much rhubarb can I pick at once?
No more than half of the fully grown stalks from a plant at one time.
Should I remove rhubarb flowers?
Yes. Snap off flower stalks as soon as they appear, because they reduce stalk production.
Are rhubarb leaves poisonous?
The leaves contain high levels of oxalic acid and should not be eaten. They are safe to compost.
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