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Green bean

Fast, forgiving and heavy cropping, and the roots leave nitrogen in the soil for whatever you plant next.

1. Wait until the soil is above 12 C. Beans sown into cold soil simply rot.
2. Build the support first for climbing types: canes 2 m tall in a double row or wigwam, tied firmly at the top.
3. Sow 4 to 5 cm deep, two seeds at the foot of each cane, and thin to the stronger seedling.
4. For dwarf beans sow 15 cm apart in rows 45 cm apart, or in blocks so they support each other.
5. Protect the emerging shoots from slugs and birds with a cloche or netting.
6. Guide the first climbing shoots onto the canes by hand, twining anticlockwise.
7. Water heavily from the first flower, and mulch the row to hold that moisture.
8. Pick every two or three days from the moment the pods reach finger length.

Soil

Well-drained soil with plenty of compost, pH 6 to 7. Beans fix their own nitrogen, so do not add nitrogen fertiliser.

Sun

Full sun, six hours or more, and a sheltered spot because climbing beans catch the wind badly.

Water

Moderate until flowering, then generous: about 20 litres per square metre per week once the flowers open, which is when pod set is decided.

Spacing

Dwarf 15 cm apart in rows 45 cm, climbing 20 cm apart at the foot of each cane

Depth

4 to 5 cm deep

Care

['Do not feed nitrogen. The plants make their own and extra gives you leaves instead of pods.', 'Mulch with 5 cm of compost at flowering to keep the roots cool and damp.', 'Pinch out the growing tip of climbing beans when they reach the top of the canes.', 'Check cane frames after any storm, since a loaded bean frame is heavy and topples easily.', 'Keep picking. Pods left to swell and go stringy stop the plant flowering.']

Harvesting

Pick when the pods snap cleanly in half and before you can see the seeds bulging inside. Hold the stem with one hand and the pod with the other so you do not tear the plant. Every two or three days at peak, and the plant will crop for six to eight weeks.

Storing

Fresh beans keep about a week in the fridge. To freeze, top and tail, blanch for two to three minutes, cool in iced water, drain and bag. They also dry well if you let the pods mature fully on the plant, in which case shell the beans and store them airtight and dry for years.

Grow it next to

Classic with sweetcorn and squash, the three sisters planting. Also good with carrots, cucumbers and lettuce grown in their shade. Keep away from onions, garlic and leeks.

Problems

[{'cause': 'Dry roots or very hot dry air at flowering time', 'fix': 'Water deeply every few days from first flower and mulch. Misting in the evening in very dry heat helps set.', 'symptom': 'Flowers open but drop off without forming pods'}, {'cause': 'Blackfly, a type of aphid that targets soft new growth', 'fix': 'Pinch out the affected tip and bin it, which often ends the problem. Otherwise spray with soft soap and encourage ladybirds.', 'symptom': 'Dense black colonies on the growing tips'}, {'cause': 'Soil too cold or too wet at sowing', 'fix': 'Wait for 12 C soil, or start in pots or modules indoors and plant out later. Mice also take bean seed, so cover the row.', 'symptom': 'Seeds never come up and rot when you dig them up'}, {'cause': 'Anthracnose or halo blight, both seed-borne bacterial or fungal diseases', 'fix': 'Remove and bin affected plants, do not save seed from them, avoid working among wet plants, and buy clean seed next season.', 'symptom': 'Dark sunken spots with reddish edges on pods and leaves'}, {'cause': 'Picked too late', 'fix': 'Pick every two or three days. Overgrown pods can still be shelled and the beans cooked or dried.', 'symptom': 'Tough stringy pods with lumpy seeds showing'}]

Saving your own seed

Straightforward. French beans are self-pollinating and rarely cross, though runner beans cross readily and need 100 m or more. Leave pods on the plant until dry and rattling, shell, then dry a further week before storing airtight. Seed stays viable three years.

Containers

Dwarf French beans are excellent in pots: a 25 cm deep container holds five or six plants. Climbing beans need at least 40 litres and a solid cane frame that will not blow over.