When it comes to feeding plants, nothing beats organic compost. Good compost contains the ideal range of nutrients which are released slowly into the ground as plants need them. Often, however, there is a valid reason to supplement plants with a fertiliser, such as when growing in less than ideal soil, or in pots and containers where the potting soil can gradually lose its nutrients. When choosing how to supplement plants the environmentally conscious gardener faces a dilemma: many commercially produced fertilisers are either chemical based or highly processed and shipped in difficult-to-recycle plastic bottles. But there is one brilliant alternative that you can grow yourself - comfrey.
Comfrey is a large herb, native to Europe, which grows prolifically in damp places such as river banks. As such, it can easily get out of control in a garden, so would not normally be deliberately introduced. However in the 1950s the organic pioneer Lawrence Hills (founder of the organisation now known as Garden Organic) developed a strain of Russian comfrey named Bocking 14 which is sterile and will therefore not seed itself all around the garden. To propagate it root cuttings are taken although these are best bought from a reputable supplier (such as the Organic Gardening Catalogue in the UK) to ensure that you get the Bocking 14 variety. It easily roots and grows very quickly so it is best to plant it in its own bed to prevent it taking over an existing area. [A word of warning: wherever you grow it don’t ever expect to eliminate it as its root system is very hard to kill]
What is brilliant about comfrey is that it contains high levels of all the essential nutrients for plant growth: Nitrogen, Phosphorus and Potassium (NPK) together with many other trace elements. Comfrey out-performs manure, compost and many liquid feeds for concentration of nutrients. It produces these from a deep root system extending right into the subsoil that most edible plants cannot access. It also has an ideal Carbon:Nitrogen ratio which means that it does not hamper absorption of nitrogen by plants. When cutting comfrey it is advisable to use gloves as the hairs on the stems can irritate skin.
There are many great ways to use comfrey around the garden:
- Mulch: Leaves can be cut and left to wilt for a couple of days before piling them around hungry plants such as potatoes and tomatoes as a thick mulch.
- Dig in: Wilted leaves can be dug into ground that is being prepared for a new crop and will break down to give an excellent feed.
- Liquid Fertiliser: Comfrey leaves can be crammed into a large container with a hole in the bottom with a small container underneath to catch the thick black liquid which will be produced in a few weeks. Weighing the comfrey down with an old brick will help this process and some people add rainwater but this does make the resulting ‘comfrey tea’ smell awful! Once produced, the liquid should be diluted 15:1 with water before using it as a leaf feed for plants such as tomatoes.
- Potting Soil: Comfrey leaves can be shredded and mixed with leaf-mould to produce a balanced soil for plants in pots, although it is a little strong for young seedlings.
- Compost Activator: Adding high-nitrogen sources is a great way to boost ‘hot-composting’ if you have the right balance of green and brown shredded material. Comfrey, being high in nitrogen, is ideal for this and should be well combined with the whole mixture rather than adding it as a layer.
Just over a year ago I planted some Bocking 14 comfrey root next to my compost bin and the growth has been astounding, despite it being a shady part of the garden that I would struggle to use for much else. (Planting it next to a compost bin is a good use of space, as vegetable plants often get eaten by slugs near compost heaps but they leave comfrey well alone.) I get three good crops of leaves each year from the plant, which can be cut right down to 2" above the ground and then re-grows vigorously. Plus, the purple flowers are great for attracting beneficial insects. Of course, I will need to keep a careful eye on it, perhaps splitting off some of the root every couple of years to prevent it getting out of control but apart from that it is so easy to grow. The resulting leaves are perfect for mulching my tomato plants and help to suppress weed growth at the same time. Comfrey really is nature’s answer to fertiliser for organic gardeners and best of all it is free – the perfect plant supplement you can grow yourself.