Organic matter goes long way in garden beds

Is it true that our garden soils can help to absorb and store carbon?

A A timely question, on the week of Earth Day this past Monday. The answer is yes, with qualifications.

We can turn our gardens into carbon sinks by continually adding organic matter to garden beds and plots and by keeping the soil covered with plants and/ or loose mulches to help keep carbon dioxide from leaking into the atmosphere.

The process of recycling leaves, young weeds, and other non-woody plant materials and turning them into compost absorbs CO2. Avoiding the use of pesticides and chemically treated fertilizers also helps to protect the active health of our garden soils while leaving the diversity of beneficial wildlife unharmed.

Whatever the size of our gardens, there is the opportunity to be partners with Nature in the earth's healing.

Q What is “leaf mould” and what is its use in gardens?

A Leaf mould is simply a collection of leaves left to compost.

Last year, I received a large bag of it, from a gardener who runs a riding mower over his fallen maple leaves every autumn. A catcher behind the mower holds the shredded leaves, which are composted in a heap.

The result is a sensual delight — earthy, light, fluffy, marvellous for mulching. That is leaf mould's most valuable role. It is a superb mulching material and soil conditioner. Not a fertilizing agent, it is mainly carbon and minerals. It is low in nitrogen.

In contrast, compost is usually high in nitrogen. Leaf mould (leaf mulch) is considered a better soil conditioner, while compost is more directly nourishing to plants. Compost and leaf mould are good partners in mulching growing plants. Compost first, with leaf mould over top. Both enhance a soil's structure and moisture retention.

Whole (unshredded) leaves will compost down into leaf mould in time, in either bags or open heaps. The composting can be helped along with the addition of a shovelful of soil to a bag of leaves.