Garden News article 22 – Mid October article

This is obviously also a bit late but hope some of the information contained within it is useful still now. Actually it is because the leaves are still falling. Not too wintery yet! 


At this time of year trees and shrubs start to reclaim some of the nutrients they have been storing up in their leaves. They take them back into their dormant buds before allowing the leaves to fall. These concentrated sugars act as a kind of natural antifreeze, helping to preserve the buds through the winter. The colour of the leaves change and we embrace our time of mellow fruitfulness.


I’m lucky to live in an area of mixed deciduous woodland so when the leaves change colour and drop they give me almost two months of viewing pleasure. The hillside opposite blushes bronze and burns with copper hues. The trees are not stupid – when they finally let their leaves drop most of the nutrients have been removed from them. What falls on the ground is little more than a carbon shell.


Not necessarily a bad thing for gardeners: sometimes a carbon rich material is exactly what we need to make good compost. Compost lovers can learn at a glance which materials are going to be good for the composting process by studying the carbon:nitrogen ratio of each. The trick is then to balance out materials that are rich in carbon (cardboard, old bedding plants, old straw, tough vegetable stems) with those that are rich in nitrogen (grass, manure, vegetable peelings, cut flowers).


For example, our old friend comfrey has a carbon:nitrogen ratio of 10:1. This means that for every one part of nitrogen you find in a comfrey leaf you will also find ten parts of carbon. Although this makes comfrey a great material for composting, if you composted the leaves by themselves you would not end up with compost but a messy slop with a very nutritious liquid run-off. This can be used as a nitrogen rich liquid feed but it is not compost.


To make compost you have to mix nitrogen rich material with something rich in carbon. Fallen leaves have a carbon:nitrogen ratio around about 50:1 so the two of them work well together – the Fred Astaire and Ginger Rogers of compost materials. Sorry, too much Strictly…


Most gardeners know that you can pile up leaves in a wire cage in the corner of your garden and let them rot into leaf mould. Nothing wrong with that – leaf mould gets plenty of organic matter back into your soil and can absorb five times its weight in water so great for supporting plants in dry soils. But you can also combine carbon rich leaves or the finished leaf mould with nitrogen rich materials like comfrey to make proper compost.


Garden Organic has developed the following recipe to do just that. You can use it if you already have some leaf mould and comfrey leaves available. If not then now’s the time to start collecting leaves for future use. In a couple of years’ time you’ll be able to make your own peat free potting and seed compost.


• Use an old dustbin or black polythene sack and fill it with alternate 7.5-10cm (3-4in) layers of 2-3 year old leaf mould and wilted, chopped comfrey leaves.
• Firm down gently and add moisture if the leaves are dry. If the leaf mould is very wet, get it out of the cage and allow to dry for a few days before making up the mixture.

• Do nothing. Leave for between two and five months or until the comfrey leaves have virtually disappeared.

• Scoop the compost out of the bin and use as a general potting compost. Alternatively add 25% horticultural sharp sand to make a seed compost.

• The pH of comfrey leaf mould is usually between 5.8 and 6.2. If a more alkaline compost is required, lime may be added.


Step by Step: Comfrey for Gardeners, Garden Organic – available from; 0845 130 1304; £1.35 plus postage.

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