Compost – uses in the garden

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After several months, vegetable peels, coffee grounds and lawn trimmings collapse into a dark, crumbly material — the same humus that decaying leaves lay down on a forest floor. Turn the heap regularly so coarse and fine waste alike break down, and you gain a free conditioner for beds, fruit trees and lawn.

• Also: compost vs soil mix

Compost is man-made humus

Humus is the most nutritious portion of soil. It comes from decaying leaves and layers the rich soil of forests. When you make compost, you re-create these conditions and transform garden waste into this “black gold”.

Converting organic matter into humus is exactly what composting does, in a natural process that takes kitchen and garden waste to enrich the soil. Items such as vegetable peels, coffee grounds, damaged fruits, lawn trimmings and weeds can be thrown in a dedicated bin outdoors or indoors, a vermicomposter, or on a simple heap of manure placed in a shady, wind-free spot.

This heap of nitrogen and carbon rich waste must be turned on a regular basis, for bits both large and fine to decompose thanks to moisture and the work of various invisible agents like bacteria, fungus, worms…

After several months, the conversion results in dark-colored compost which has acknowledged properties supportive of soil and plant life. The richer the compost, the darker the color.

How to use compost

When mature, compost can be used in various places in your garden.

• Mixed with soil mix, you can spread a thin layer to serve as a growing medium on flower and vegetable beds.
• It contributes to plant growth, as long as they aren’t planted directly into the compost (except for plants like squash that love it).
• A layer of more neutral soil is needed between the compost and the seeds. This helps avoid “seedling burn“, where too much nitrogen kills seedlings off.

When to add compost to soil

Adding compost to the ground is best done in fall and at the end of winter.

• It is also possible in spring in the form of mulch between vegetable rows, but the amount of compost added varies depending on the type of plant grown.

Compost and trees

Compost is also useful when planting fruit trees, and to upgrade the soil after a few years. Add a thin layer of compost topped with straw around the tree trunk and across the entire surface shaded by leaves (the “drip line”).

• This is called “topdressing” in the gardening slang.

Topdressing lawns

If sifted gently among the blades of grass in spring, compost helps a lawn grow evenly (also called topdressing for a lawn). Compost also helps shrub hedges and perennial plants grow well when added as a soil conditioner. Finally, use it to fill in garden boxes, mixing it together with one part soil and one part sand.

• When top-dressing an established lawn with compost or sand, spread only about a quarter-inch at a time so grass blades still show through, since completely burying the leaves can smother the turf.
• Mow the lawn first, then work the compost down among the blades with the back of a rake or a stiff broom.
• Topdressing pays off most just after scarifying or aerating, since the compost falls into the holes and reaches the root zone.

Where to use compost, and how

Mature compost is not spread the same way everywhere. The table below sums up the places the article covers, the way compost is applied in each, and the moment to do it.

In every case the rule is the same: compost enriches the soil around plants rather than replacing it.

Foster biodiversity

Last but not least, that pile is a excellent way to attract beneficial animals to the garden. Worms, scavenger insects and even hedgehogs or other cute critters may find that healthy pile of material appealing! Healthy soil thanks to compost is one of the core concepts behind permaculture.

• Read all our pages related to compost
• More soil amendments to try out in the garden: ashes, BRF, hydrogel…

• Stand the bin on bare soil rather than paving, so worms, ground beetles and centipedes can move up into the waste of their own accord.
• Check the heap before plunging a fork into it, since hedgehogs, slow-worms and toads shelter in the warm lower layers.
• Keep meat, fish and cooked leftovers out of the heap, as they draw rats rather than the helpful visitors.