Blue Lupins are a hardy annual green manure that can be planted from March to July and are part of the legume family. They suit light sandy acid soils and are a hardworking leguminous plant that has very long tap roots that dredge up minerals. (Lupins fix 25% more free nitrogen than clovers and 28% more than peas and beans). The long roots also help to break up and aerate heavier soils and allow more moisture retention with the addition of humus from the break down of the roots on light sandy soils.
Lupins produce a beautiful blue flower but it is best to dig it in and cut down before they flower to help prevent them seeding and then becoming a nuisance. The flowers are great for insects so a few could be left to flower to draw more insects into the vegetable area.
It is possible to sow lupins as an intercrop, e.g. among long growing varieties of veg like cabbage and sprouts, where they will contribute nitrogen to the soil (once they are dug in) and help promote growth in the veg crop. Treat as a legume for crop rotation purposes so great before nitrogen hungry crops like brasssicas.
Lupins can be slower to germinate than other green manures.
