Cilantro

Shoots up a thin central stalk and the new leaves come through fine and ferny

Bolting. Cilantro is a cool-season annual that reads warmth and long days as the signal to flower, and a heated room reads as summer all year round.

Fix: Keep it in the coolest bright spot in the house and sow a new pot every two or three weeks. Once the stalk is up, let it run. The seed it sets is coriander.

Transplanted seedlings sit still for a fortnight, then yellow off

Like the rest of its family it puts down a taproot early, and it does not forgive having that broken.

Fix: Sow straight into the final pot and thin to the strongest seedlings rather than moving them. A supermarket pot is usually a dozen plants crammed together. Split the block into two or three clumps without picking the roots apart.

One good harvest, then the plant gives up

Cut too hard and too low. Everything regrows from the crown, and taking the lot at once leaves nothing to rebuild from.

Fix: Take outer stems at the base and leave the small central leaves alone. Four or five plants in rotation will give you more over a season than one large plant ever does.