Rhubarb

Rheum × hybridum

Rhubarb comes back year after year and you pick its tart stalks from spring to early summer. Only eat the stalks. The leaves contain oxalic acid and must never be eaten. One clump keeps going for many years. Every five years or so, dig it up, cut it into a few pieces and replant them to keep it strong.

Looking after it

Water: Normal watering is all rhubarb needs. Water new plants in dry spells right through their first season. After that, a settled clump only needs water in long, dry summers. Never let the crown, the base of the plant, sit in soggy soil. Feeding: Rhubarb needs an average amount of feeding. Each spring, spread a 7 cm layer of well-rotted manure or compost around the plant. Keep it off the crown, though. On poor soil, also give a high-nitrogen feed in spring.

Harvest and keeping

In the second year, pull only a few stalks. From the third year on, pick stalks about 30 cm long. Hold each one at the base and twist it off instead of cutting it. Never take more than a third of the stalks at a time. Stop in early July so the plant can recover. The stalks keep about a week in a bag in the fridge. Put the leaves on the compost. Chopped stalks freeze well too.

What can go wrong

Crown rot. The crown goes soft and brown and the buds die, usually in wet soil in winter. Cut out the rotten parts straight away. If the whole crown is affected, replant healthy pieces in fresh ground that drains well.
Flower stalks. Tall, thick stems with a big flower head take strength from the plant. Cut them off at the base as soon as you see them.
Slugs and snails. They eat the young shoots in spring. Check the plants after dark and pick them off.

Growing facts: RHS, UC ANR and seed-company sowing guides. Rhubarb care: RHS. How many to grow: University of Missouri extension. pH: Cornell and University of Maryland extension.