Ben Raskin answers your questions about French beans
Post categories: french bean,Ìýquestion
| 08:38 UK time, Monday, 14 June 2010
gardening expert Ben Raskin answers your questions about growing the Dig In French beans. If you have a similar story to share, you can add your comments at the bottom of this entry. You need to register first, which only takes two minutes.
John Pritchard asks: After planting my French beans out in the garden the previously beautiful green plants are beginning to turn yellow from the ground upwards. Have I overwatered during a period without much sun? Or are they in need of a nitrogen-rich fertiliser?
Answer: It is possible though unlikely that you would have overwatered outside, this is much more of a problem in pot-grown plants. French beans certainly don't like it too wet and cool. I would recommend a really good soak when you plant them out and then only water them if it is really hot and dry (and even then maybe only once every couple of days). Watering will have an impact on yields though, so once they start fruiting then keep them watered during hot weather.It is also possible that your soil is low in organic matter and therefore they could do with a boost (though again legumes often suffer less from this than other plants as they are able to fix their own nitrogen once they get going). I would suggest giving them as liquid feed with seaweed. This can act as a tonic, indeed many growers will dip the roots of transplants in a weak seaweed solution before planting out.
Dot Stanley asks: I have heard that peas and beans fix nitrogen in the soil. Is this a good thing and if so which veg would benefit? (subsequent crop) Also, if this is a useful thing what do I need to do, leave plants in ground until withered and dead or something else?
Answer: You are right that members of the legume family (which peas and beans are) have a symbiotic relationship with soil bacteria which are able to fix nitrogen (N) from the air. The plant gives the bacteria sugars from its roots and in return gets N. To check whether this is happening you can dig up a root and look for white lumps or nodules on the bean/pea roots.
I will try and keep my answer a little brief (I get quite excited about all of this if I'm not careful!). The peas and beans benefit from increased N availability; however, it is a slight misconception that following crops will have more N, as most of the N is taken away when you harvest the beans. What it does mean is that the plants are 'N neutral' ? that is, will not deplete the N reserves from your soil. This means that they are good for putting at the end of your rotation, just before a fertility-building phase.
Leaving the plants behind to go back into the soil will certainly help and would ensure that you had a population of the bacteria present for the next time you grew peas in that spot.
Incidentally clovers and tares/vetches are also nitrogen fixing, and undersowing crops can help bring N into your soil. I would recommend trying to under-sow large brassica crops with yellow trefoil for instance.Jilly Cotterell asks: I've made nettle fertiliser, which I'll dilute with water. Are there any veg, flowers or bushes etc. where it would be harmful to put nettle fertiliser? Thank you. And thanks very much for the seeds!
Answer:: Hi Jilly, as far as I know there are no plants that would be damaged by a good nettle feed.
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