Sow the seeds indoors in early spring in a seed tray filled with potting compost. Cover the seeds with a 1-inch layer of compost. Keep the compost moist but not soaked.
Thin out the beans when the shoots have grown to about 1 inch, removing the weakest-looking seedlings.
Add a 3-inch layer of well-rotted compost to the top of the soil where the bean will grow. Dig down to a depth of 9 inches, mixing the compost in well with the soil.
Remove the bean seedlings from the seed tray after the last frosts have passed. Avoid damaging the young roots. Use a trowel to dig holes deep enough to take the whole root, spacing the seedlings about 12 inches apart in rows 2 feet apart.
Place the seedlings in the holes and backfill with compost, firming it down. Water thoroughly. Keep the soil around the beans moist as they grow.