Hügelkultur: When logs start to rot they get spongy and hold lots of water, and as the rot they release fertility. This is the magic formula that makes hügelkultur ( a German term) work. Essentially you dig out a 1m wide trench, putting the topsoil to one side, fill the trench with logs, then put on layers of branches, twigs, compost and green waste (like lawn clippings). Then when you have a pile that is 1-2m high you layer the soil back on top. It takes 20-30 years for all the logs and branches to rot fully down leaving you with level ground again and in that time you have a raised bed perfect for hungry and thirsty crops like courgettes, squash, strawberries and salads.

It’s a lot of work, and for most gardens, impractical as a wagon-load of logs and branches are not available, but in a woodland environment a glade-full of hügelkultur beds is a sustainable way of converting forest fertility into sustainable crop production.

Ramial: It’s the twigs and small branches (lop and top) of a tree that contain the highest fertility. When this is chipped or shredded and used as a soil additive it is called ramial (a French-Canadian term). Studies have shown that the application of ramial to agricultural crops will increase organic matter, significantly increase worm activity and protect against pests and diseases as well as smaller fertility benefits.

These twig-wood clippings are often a bane for gardeners to find a use for, but shredding it and applying directly to vegetable growing areas is every bit as good as composting it first. A good deal for a lazy gardener.

Biochar: The Rolls-Royce of tree-based soil improvement! Biochar is charcoal produced under more controlled conditions and higher temperatures than normal charcoal. Biochar can be made out of wood or any organic material (manure, straw or even dried sewerage sludge) and put into a special biochar kiln. The resulting charcoal is then crushed and ‘activated’. Activation is normally by soaking in a compost tea made out nutrient rich green matter such as seaweed, nettles or comfrey. The biochar is then added directly to soil or added to compost for use. Biochar adds no fertility to soil directly, but its microscopic honeycomb structure creates massive surface area that increases the capacity for soil to retain nutrients and water. Biochar also improves soil structure and has properties that enable it to neutralise diseases and contamination (like lead). These contributions to soil heath lead directly to plant health improvements that can even confer resistance to diseases like ash die-back.

One of the main reasons for using biochar is that the carbon in the char is locked up for hundreds or even thousands of years making it a potent climate change mitigation product.