Gadenin日本語Get the appFeed it far more heavily than the rest of the garden
An established rhubarb crown produces an enormous amount of leaf and stalk from a fixed patch of soil, year after year, without ever being lifted or rotated. Nothing else in a vegetable garden works that hard in one place. If the stalks are getting thinner and shorter each season, the first thing to suspect is hunger, not disease.
The main feed goes on in late autumn or early winter, after the leaves have collapsed and been cleared away. Spread two to three inches (5 to 8 cm) of well rotted manure or rich compost in a ring around each crown, out to about eighteen inches (45 cm), and keep it off the crown itself. Rain and worms take it down over winter and the spring flush comes through it.
Give a second, lighter feed in early spring as the first buds move: a general purpose fertilizer high in nitrogen, scattered around the crown and hoed in lightly. Do not dig it in deeply. The feeding roots sit close to the surface and a spade among them does more harm than the fertilizer does good.
| Timing | What to apply | Why then |
|---|---|---|
| After the leaves die back | Thick mulch of rotted manure around the crown | Feeds the roots and protects them through winter |
| As buds break in early spring | Nitrogen rich general fertilizer, hoed in lightly | Drives the leaf growth that fills the stalks |
| When you stop pulling | A light second dressing plus a fresh mulch | Helps the crown rebuild before dormancy |
| Any time | Nothing directly on the buds | Material against the crown holds damp and causes rot |
Water deeply in drought, never little and often
Those huge leaves lose a great deal of water on a hot day, and the first symptom of drought is stalks that are thin, stringy and short. A crown under water stress will also throw a flower spike far sooner than a well watered one, so watering and bolting are the same problem.
In a dry spell, soak each crown thoroughly once a week rather than sprinkling it daily. Aim for enough to wet the soil a spade deep, which on most ground means two full watering cans per mature crown. A four inch (10 cm) mulch of compost around the plant will halve how often you need to do it.
Some midday wilting in full sun is normal and does not mean the plant is short of water. Judge by whether the leaves have recovered by early evening. If they are still limp at dusk, water; if they perked up on their own, leave it.
Rhubarb in a large container dries out several times faster than rhubarb in the ground and needs checking every day in hot weather. A pot smaller than about twenty inches (50 cm) across will never grow a good crown.
Cut out flower spikes the moment you see them
Sooner or later a thick, blunt, cauliflower-like bud will appear in the middle of the crown and shoot upward into a tall flower stem. It is not a sign that anything is wrong with you, but it is a serious drain on the plant. Producing flowers and seed takes energy that would otherwise go into next year's stalks, and stalk production drops off sharply while the spike is growing.
Remove it as soon as you spot it, while it is still short and easy to reach. Follow the flower stem down to the base and cut or snap it off as low as you can get, right at the crown. Do not leave a long hollow stub standing, since it collects water and rots down into the crown. Check the middle of every crown each week through spring; a spike can go from a fist sized bud to three feet (90 cm) tall in a fortnight.
Repeated flowering usually means one of three things: the crown is old and congested and needs dividing, it went short of water, or it is hungry. A crown that flowers two or three years running is telling you to lift and divide it in the coming dormant season.
The leaves are poisonous, the stalks are not
Only the leaf stalk is edible. The leaf blade itself contains enough oxalic acid and other compounds to make people seriously ill, and it should never be eaten, cooked, juiced or fed to livestock. This is not a folk caution; it is the reason every stalk is trimmed at the top before it goes indoors.
Trim the leaf off outdoors as soon as you have pulled the stalk, and cut generously so no green blade goes into the kitchen. The leaves are perfectly safe to compost. Oxalic acid breaks down readily in a compost pile and there is no residue that harms the following crop, so the leaves go straight on the heap or under the hedge.
Keep the trimmed leaves out of reach of children and pets while they are still fresh and tempting looking. Once they are on the heap and wilted they are of no interest to anyone.
Give it a long rest and keep a note of the season
The most important piece of care is stopping. Once you have finished picking, usually by around midsummer, leave every remaining leaf on the plant for the rest of the season. Those leaves are rebuilding the reserves that produce next spring's stalks, and a crown stripped bare in late summer comes back weak.
Let the foliage die down naturally in autumn rather than cutting it green. When the leaves have collapsed and yellowed, clear them away so slugs and rot have nowhere to overwinter, then mulch. Clearing the dead foliage matters more than tidiness suggests, since it removes a great deal of the material that carries crown rot into the following year.
Keep a short record for each crown: the date the first bud broke, the date you started and stopped pulling, roughly how many stalks it gave, and whether it flowered. Two seasons of that turns vague impressions into a clear picture of which crown is thriving and which one needs dividing.