HOW TO USE COMFREY AS AN ORGANIC FERTILIZER
.For any gardener who wishes to grow their plants by using strict organic principles, modern fertilisers can often be a bit of a sticking point. However, help is at hand from the native European herb Comfrey – otherwise known as ‘Knitbone’ as it was once used as a traditional remedy to help heal broken bones.
Comfrey has a naturally deep rooted and extensive root system which acts as a dynamic accumulator by extracting a wide range of nutrients from deep within the soil. These nutrients naturally accumulate within its fast growing leaves - up to 4-5 lbs per plant when cut. Because comfrey leaves lack fibrous tissue they can quickly break down returning their nutrients to the soil surface making them more readily available to cultivated plants. In addition there is little risk of nitrogen being ‘locked up’ during decomposition when comfrey is dug into the soil as the carbon to nitrogen ratio of the leaves is lower than that of a well-rotted compost. Comfrey is also an excellent source of potassium - an essential plant nutrient needed for flower, seed and fruit production. In fact comfrey leaves contain 2-3 times more potassium than most farmyard manures.
There are various ways in which comfrey can be utilized as a fertilizer, the most common are as follows:
Comfrey can be used as a compost activator - Add comfrey to a compost heap to add nitrogen. Its speedy decomposition will also help to heat the compost heap. However, comfrey should not be added in large quantities as it will quickly break down into a dark sludgy liquid that will need to be balanced with more fibrous, carbon rich material.
Comfrey liquid fertilizer – This can be produced by either rotting leaves down in rainwater for 4–5 weeks to produce a ready to use 'comfrey tea’, or by stacking dry leaves under a weight in a container with a hole in the base. When the leaves decompose, a thick black comfrey concentrate can be collected. This must be diluted at a rate of 15:1 before use.
Comfrey as a mulch or top dressing – By applying a 2 inch layer of comfrey leaves around your chosen plant, it will slowly break down and release a range of plant nutrients. It is especially useful for crops that need extra potassium, such as fruiting plants, but there is also evidence that it can improve potato crops too. Comfrey can be allowed wilt slightly before application but however you use, avoid using flowering stems as these can take root.
Comfrey potting compost – This was originally developed to be used in conjunction with peat, but environmental awareness has led to a leaf-mold based alternative being adopted instead. Two year old, well decayed leaf mold should be used, as this comfortably absorbs the nutrient-rich liquid released as the comfrey decays. Using a black plastic sack, alternate 3-4 inch layers of leaf mold followed by 3-4 inches of chopped comfrey leaves. Add a little dolomitic limestone to slightly raise the pH level. Leave for between 2–5 months depending on the season, but make sure that you check that it does not dry out or become too wet. The mixture will be ready when the comfrey leaves have rotted and are no longer visible. This mix can be used as a muli-purpose potting compost, although it will be too rich for seedlings.
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