Date: October 2, 2022

Types of compost

We make compost in lots of different ways, from lots of different materials. This short blog describes a bit about some of them.

Green waste compost:

This is what we make from the waste and debris from tidying up our gardens: hedge trimmings, grass cuttings, weeds etc. If we make it properly – balancing any wet squidgy grass with lots of brown materials, ensuring that the mix is neither too wet nor dry, dense nor loose – then it is easily done. We can either use the quicker but more labour-intensive hot composting method, or a slower cool composting method.

The resulting compost should be crumbly and spongy. It will greatly improve soil health, structure, and microbial population. It will facilitate the best combination of drainage and moisture retention, increase soil microbial populations, and encourage earthworm activity.

Its nutrient value for plants will depend on what ingredients went into making it – grass cuttings and weeds contain a lot of nutrients that will become available in the finished compost. Green waste compost from woodier materials will be a bit more acidic and fungally-dominated, and will especially suit perennial plants. Compost containing more green materials will be more bacterially dominated, which is good for annual plants.

Worm castings:

Castings is the name for worm poo, or compost produced when worms eat stuff and digest it.

Worms are an effective solution to composting fruit and veg waste, and a wormery can work well in a small space where many other composting systems are not an opetion.

Worm castings tend to be dense and moist. They cannot be used as a growing medium on their own, but can be very beneficially mixed with other soil or compost, or used as the basis for a compost tea feed for plants.

Castings are usually derived from fruit and veg waste, so they contain a lot of nutrients which are slowly released. They are an excellent addition to the soil for hungry plants, as a top dressing to be watered in, or as an ingredient in a potting mix.

Worm castings contain a lot of beneficial bacteria and enzymes, and help to support disease and pest resistance in plants.

Leaf mould:

Leaves from deciduous trees, if kept in a moist and aerated environment, will decompose by a fungal process into leaf mould. The process takes two years, although this timescale can be shortened by shredding the leaves.

Some people also accelerate the process by adding high-nitrogen amendments such as grass cuttings, coffee grounds, nettle tea or even urine, but strictly speaking this is not pure leaf mould as the extra nitrogen changes the biological processes involved.

Leaf mould has a wonderfully loose and crumbly texture. It is low in nutrients so it is an excellent medium for propagating seeds – especially those of woodland trees, for which it is their natural growing environment.

Leaf mould has a high fungal content and encourages development of mycorrhiza, which facilitates plants to regulate and optimise their intake and exchange of nutrients and water with soil organisms and other plants nearby.

Adding leaf mould to soil improves its structure and moisture retaining properties. Leaf mould is slightly acidic, and is beneficial to acid-loving plants and perennials.

Date: March 6, 2019

Leaf Mould – it never gets old!

Leaf mould is such wonderful stuff. Friable, crumbly, smelling of the forest floor.

It is great for adding to garden soil or raised beds, where it helps to loosen the soil and to retain moisture while also aiding drainage – how cool is that?

Leaf mould also works brilliantly as a seed or potting compost because of its texture and its low macronutrient content – composts high in macronutrients will most likely result in unhealthy growth in seedlings. I recently had the pleasure of supplying leaf mould for a “Forest in a Box” project This is a way for schools to propagate native trees in a 1×1 metre wooden box, protected from rodent predation with wire mesh above and underneath. Forest in A Box
Forest in a Box

The page linked above says that this space can produce 200 healthy trees for planting out every 2 years, so what a great use of a small space!

The beauty of leaf mould in this setting is that it provides the same fungi and microorganisms as the forest floor, so the tree seedlings feel right at home. The walls of the box encourage the trees to reach for the light, just like in the forest where competition for resources makes trees work harder and become stronger, though trees also help each other in surprising ways – plants are very altruistic creatures!

The mycorrhizal fungi that help plants such as trees to take up nutrients in a mutualist, symbiotic relationship between plant and fungus, also allow trees and other plants to pass on nutrients and even water to their neighbouring plants that need them.

And of course, these mycorrhizal fungi are present in the leaf mould. Leaf mould also contains valuable minerals – trees uptake minerals from deep in the subsoil using their roots, and when they shed their leaves they release some of these minerals. So whoever collects the leaves and makes leaf mould is also collecting the minerals that they contain!

Bagged leaf mould ready to go! – these leaves were dropped in 2016 so they are now fully composted, with no leaf structure left – see top image of leaf mould in hand.
leaf mould pile
A pile of sieved 2 year old leaf mould