Here are some green plants that can be used as fertilizer in the UK:
Comfrey
Rich in potash, comfrey is useful for flowering and fruiting plants and vegetables. To make a liquid fertilizer, add 1kg of comfrey leaves to 15 liters of water and leave it in a sealed container for six weeks. Then, use it undiluted.
Nettles
High in nitrogen, especially in spring, nettles can be used as a liquid fertilizer. To make a liquid fertilizer, add 1kg of nettles to 10 liters of water, leave it for about two weeks, and then use it at a dilution rate of 10:1.
Green manure
Plowing living plants into the soil is a practice called green manure that can enhance soil fertility. This releases nutrients slowly, which supports microbial activity and benefits plant growth. For example, incorporating green manure crops like legumes can add nitrogen to the soil, improving crop yields.
Other organic fertilizers that can be used in the UK include seaweed, hoof and horn, dried blood, fish blood and bone, bone meal, and poultry manure pellets.
However, did you know you also can use herbs you grow in your garden to build your soil? Plants such as borage, comfrey, fenugreek, sorrel and many others can help the soil to accumulate nutrients, reduce soil compaction, act as cover crops or