My rhubarb has sent up a huge flower spike — what should I do?
A bolting rhubarb crown is telling you something about its age or its conditions — cut the spike out at once, and read what triggered it.
- Difficulty
- beginner
- Time
- 10 min
- Read
- 3 min
Short answer
Cut the flower spike out at the base as soon as you see it, before it opens. Flowering is triggered by age, stress or a hot dry spell, and it drains a large amount of energy into seed the plant should be putting into stalks. If it happens every year, the crown needs dividing, feeding and mulching.
The first time a rhubarb crown throws up a thick asparagus-like stem topped with a cauliflower of creamy flowers, it is startling. It is a normal thing for the plant to do and it is not a disease, but it is worth reacting to promptly and worth understanding, because the plant is telling you about its condition.
Step by step
- Cut the spike out at the base immediately.Follow it down to where it emerges from the crown and cut it off as low as you can reach with a sharp knife. Do it before the flowers open — seed production is where the energy goes.
- Check for further spikes over the following weeks.A crown that has decided to flower often produces two or three. Keep looking and remove each one as it appears.
- Do not panic about the crop.The stalks around a flowering crown are perfectly good to eat. Flowering does not make rhubarb toxic or unpalatable, it just diverts energy.
- Ask whether the crown is old and congested.Age is the most common trigger. A crown that has been in the same place for many years and is producing thin stalks alongside flower spikes needs lifting and dividing in winter.
- Look at whether it went dry.Drought stress is a common trigger. Rhubarb has enormous leaves and needs a lot of water. A thorough soak in dry spells and a heavy mulch reduces it.
- Feed and mulch the crown.A hungry crown is a stressed crown. Mulch generously with well-rotted manure or compost around the plant each autumn, and give a general feed in spring.
- Ease off the picking that year.A crown that has flowered has already spent energy. Take a lighter crop and stop earlier than usual to give it a chance to rebuild.
- Accept some varieties simply flower more.Some varieties are considerably more prone to bolting than others, and an old unnamed crown from a previous owner may be one of them. If it flowers every year despite good treatment, replace it with a named modern variety.
Tips
- The flower spike is edible while it is still tight and green, cooked like a thick asparagus spear, though most people find it unremarkable. Cutting it out is the priority either way.
- Rhubarb flowering is far more common after a hot dry spring, so a bad year for it across the whole garden usually points at the weather rather than the plant.
- Leaves, flowers and seed heads are all high in oxalic acid — do not eat them and do not feed them to animals. They compost perfectly well.
- A newly planted crown that flowers in its first year is usually just stressed by the move. Cut it out, keep it watered, and take nothing that season.
Common mistakes
- Leaving the spike to flower because it looks impressive — Seed production takes a great deal from the crown, and it is energy that should be going into next year's stalks.
- Snapping the spike off partway up — It regrows from the stub. Cut it at the base, as low as you can get.
- Ignoring a crown that flowers every year — It is a signal, usually of age and congestion. Dividing and feeding fixes most repeat offenders.
Questions people ask
Is rhubarb still safe to eat after it has flowered?
Yes. The stalks are unaffected and perfectly good. Only the leaves and the flowering parts are high in oxalic acid and should not be eaten, which is true whether or not the plant has flowered.
Should I let it set seed to grow more plants?
Not worth it. Rhubarb from seed is variable and takes several years to produce, and it will not come true to the parent variety. Dividing the crown gives you identical plants in one winter afternoon.
Will it flower again next year?
It may, particularly if the trigger was age. Divide and feed the crown in winter and most plants stop. If it still flowers annually after that, the variety is prone to it.