Comfrey: the wonder plant
If you do just one thing to make your gardening more sustainable, plant a comfrey patch.
This is mine: it’s just 60cm x 60cm (2ft x 2ft) and provides me with a constant supply of totally renewable, organic, plastic-free and pollution-free fertiliser. And it brings in the bees – which will hopefully pollinate my beans and courgettes while they’re about. Comfrey also makes a great poultice for healing bruises and sprains - its old mediaeval name was knitbone.
Comfrey leaves grow big, jungly and green, and like most lush growth that means they are full of nutrients which can help your plants. Analyses of its mineral proportions can vary, but most give it a value of around 3% nitrogen (N – for leafy growth) to 1% phosphorus (P – for roots) to 5% potassium (K – for flowers and fruits). This last is the most eyecatching: it’s around five times higher than, for example, seaweed or clover. And that’s why comfrey makes such a great substitute for tomato feed.
It's not as strong: the NPK values for a leading brand of synthetic tomato feed are 4:3:8. So, you might argue, why would I ditch my regular tomato feed and use something less potent instead?
Well: synthetic fertilisers are made using the Haber-Bosch process – also known as ‘bread from air’. It pulls nitrogen from the air to make ammonia – an excellent fertiliser which is the base of pretty much all synthetic plant feeds you’ll buy.
But the Haber-Bosch process uses vast quantities of energy – most of it from burning fossil fuels. In addition, as you apply your synthetic fertiliser up to 5% is released into the air again as nitrous oxide, one of the most potent of all greenhouse gases. So for every 1kg of synthetic fertiliser you use in your garden, you add about 2.7kg of greenhouse gases to the atmosphere, actively contributing to climate change.
And who would do that, when you can have a fertiliser that may not be quite as potent but which does much the same job, is plentiful, renewable and free, avoids plastic pollution, and (unlike synthetic fertilisers) adds organic matter to the soil - actively sequestering carbon as it feeds your plants?
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