It is best to harvest all your broad beans before they reach the black scar point. It is easy to prepare them for the freezer. Just pod them and then drop them into a pan of water on a rolling boil. Boil them for 2 to 3 minutes, until you see a colour change then drain them and run them under a cold tap to cool them quickly. Lay them onto open trays and place them in the freezer. Once frozen, remove them from the tray into labelled bags to use in the autumn or winter.
When you have harvested all your beans, chop your broad bean plants down so that there is about 10 cm of stem left above the ground and give them a good watering. If you are lucky then the plants will regrow from these stems and flower again to give you a second small crop of late broad beans before the season ends.
Of course, you may by now have past the point of perfect maturity for freezing your beans and only have old beans left that will be unpleasant to freeze. If this is the case then you might like to try making broad bean pate or hummus. These recipes requires cooking the beans first and then removing the tough outer skin to use the middle of the bean only. It's a bit fiddly but it does make use of beans that might otherwise go to waste.
Bean and Pea Pate
260g broad beans
100g peas (frozen are fine)
¼ teaspoon each ground cumin and coriander
Salt and pepper
1 clove garlic
2 tablespoons of natural yoghurt or soya alternative
Boil the broad beans for 5 to 10 minutes then drain and allow to cool. Remove the outer skin from the beans and place in a food processor. Boil the peas for 3-5 minutes and allow to cool before putting them in the food processor too. Finely chop the garlic and fry in a little oil for about 3 minutes then add to the peas. Add the spices and salt and pepper to taste, along with the yoghurt. Blend all the ingredients until a smooth pate forms. Decant into suitable containers. Refrigerate for up to 4 days or freeze.
Broad bean hummous
650g podded broad beans
½ teaspoon ground cumin
3 tablespoons lemon juice
1 tablespoon olive oil
Good pinch salt
Pepper to taste
Clove of garlic
Cook the broad beans then drain, cool and remove the outer shell. Put all the ingredients in a food processor and blend until smooth. Can be frozen.
If you have reached this stage of maturity, it is also possible that your broad bean plants are past their best too and there is probably no point cutting them down for a second flush. Instead, if you can afford the space, leave at least some of the plants to stand until they die back and turn into dead, dried stems. Broad beans are one of only a few plants that grow hollow stems so come the winter you can chop them up into short lengths, pack them tightly into a cut off drinks bottle and hang them up in a tree so that insects can crawl into them to overwinter.
One thing that is worth bearing in mind at the end of broad bean crop is that they are part of the legume family. This family has nitrogen-fixing bacteria living in nodules on their roots. These bacteria can do something quite amazing that humans can only do by complex chemical process that require a great deal of energy; they can extract nitrogen from the air. As a result, nitrogen levels in the soil increase and this in turn improves the fertility of the soil. It is therefore important when clearing away old broad bean plants to leave the roots in the soil so that you leave these nodules (and the associated nitrogen) in the soil too. It is very easy to pull a broad bean plant out of the ground completely, roots and all (I sometimes do this by accident when trying to harvest the beans!), but instead, you should chop the plants down to soil level and fork the roots over into the soil to help improve the soil.