If you want to show off their unique colour — and why not — you’re best to serve these raw or just barely-blanched in salads.
There are two very popular varieties. Both can be planted quite early in the season. Both varieties taste pretty much the same as standard green beans.
Royal Burgundy takes about 55 days from seed being planted to produce pods 5 – 6 inches long (15 cm.)
Purple Queen will flower 42 days and produce beans about 55 days after seeds are planted. The pods are very deep purple, much darker than Royal Burgundy. Even the leaves on the plant are a purply-green.
If you want to blanch these for use in a salad, but still retain their purple colour, plop into boiling water and DO NOT walk away from the stove. Blanch for 1 to 2 minutes, but don’t go over the 2 minute mark. Get them off the stove, drain them, and plunge into cold water to stop them cooking right then and there.
1 pound (450g) purple beans = 30 – 40 beans = 3 1/2 cups untrimmed = 3 cups topped and tailed = 2 3/4 cups chopped.
Store in the refrigerator for up to 5 days tightly wrapped in a plastic bag.
Freezing: Wash the beans, top and tail them. Cut them up, and blanch in boiling water for 3 minutes (no more!) Plunge into very cold water to cool them, then drain well, pack and freeze for up to 6 months.
Developed in the Nantes area of France.