Compost Types: Which to Choose

Plant compost is made from broken-down plant material. Leaf compost and yard-waste compost fall in this group. They come from leaves, grass clippings, trimmings, and other green waste that has decomposed into dark, crumbly matter. It is the most common general-purpose compost.

Leaf compost, sometimes called leaf mold, is made mostly from fallen leaves. It is mild and light. It improves the structure of the soil and helps it hold moisture. It is gentle enough for most beds and for mixing into a broad range of plantings.

Yard-waste compost is a broader mix of green material. It is a solid, all-around amendment for garden beds and for improving tired soil. It adds organic matter that loosens heavy soil and feeds the life within it. It is widely available in bulk from landscape yards.

This type is a safe default when you are unsure what to buy. It is mild, so it rarely burns plants, and it suits most beds and general soil improvement. It is a fine choice for working into a garden bed or blending into a raised-bed mix.

Use the compost calculator to size a plant or leaf compost job. Enter your area and the finished depth for a bed, or the bed volume and compost share for a raised bed. The tool reports the cubic yards and tons. Add the overage allowance so you order enough to reach depth after the compost settles into the soil.

Composted manure is animal manure that has fully broken down. It comes from cattle, horse, poultry, or other livestock, aged and composted until it is stable and dark. The key word is composted. Fresh manure is not the same thing and is not ready for the garden.

Composted manure is rich in nutrients. It is a strong feeding amendment for vegetable gardens and hungry beds. It adds both organic matter and a nutrient boost, which is why gardeners reach for it where plants need a lot of feeding. It is a workhorse for productive beds.

Because it is rich, use it in the right amount and in the right place. Work it into a bed rather than piling it thick around plants. Too much rich manure in one spot can be strong for tender roots. Blend it into the soil so the nutrients spread through the root zone.

Always buy manure that is fully composted. Fresh or raw manure can burn plants and carry weed seeds and pathogens. Aged, composted manure has broken these down and is safe to work into the soil. Ask your supplier to confirm the manure is fully composted before you order.

Size a composted-manure job with the calculator like any other compost. Enter the area and the depth you plan to work into the bed. Add the overage allowance, since the material settles into the soil as you turn it in. Order by name, and confirm with your supplier that the product is finished and ready to use.

Mushroom compost is the material left over from growing mushrooms. Growers use a rich blend to raise a mushroom crop, and the spent material is sold afterward as compost. It is also called spent mushroom substrate. It is a popular, widely sold amendment.

Mushroom compost is a good general soil conditioner. It adds organic matter and improves the body of the soil. It works well turned into garden beds and blended into planting soil. Gardeners value it as an affordable, effective way to enrich a bed.

Mushroom compost can carry salts from the growing process. Fresh from the source, it may be strong for salt-sensitive plants. Many suppliers age it to bring the salts down. Where you are planting something sensitive, blend it into the soil rather than using it heavy, and water the bed well after you work it in.

Use mushroom compost where you want to improve soil for general planting. It suits vegetable beds, borders, and mixed plantings that benefit from more organic matter. Work it into the existing soil rather than leaving it in a thick layer on top, so it blends into the root zone.

Size a mushroom-compost job with the calculator the same way as any compost. Enter the bed area and the depth you plan to work in. The tool reports the cubic yards and tons. Add the overage allowance for settling, and ask your supplier whether the compost has been aged before you order.

Blended garden compost is a ready-made mix built for general garden use. Suppliers combine several composts and amendments into one balanced product. The blend aims to be an all-around soil improver you can use across a garden without thinking hard about the parts.

A blended compost is a convenient choice. It saves you from mixing your own and gives an even, consistent product. It suits working into beds, blending into a raised-bed mix, and general soil improvement. Ask your supplier what the blend contains so you know it fits your plants.

Worm castings are a different and more concentrated product. They are the rich, dark material worms leave after they digest organic matter. Castings are potent, so you use them in small amounts. They are not a bulk fill for a whole bed.

Because castings are strong and used sparingly, gardeners mix a little into planting soil or work a thin amount around plants. A small quantity goes a long way. They are often sold in bags rather than by the bulk yard, which fits how little you use at a time.

Size a blended-compost job with the compost calculator by area and depth, like any bulk compost. Worm castings are different. You use so little that you measure them by the bag or the small amount a plant needs, not by the cubic yard. Use the calculator for the bulk compost, and add castings on top as a concentrated boost.

The right compost depends on where you are using it. Lawns, garden beds, and raised beds each ask something a little different. Match the type to the place before you order.

For a lawn, use a mild, finished, screened compost. A top-dressing must spread thin and even between the grass blades, so the compost has to be fine and free of large chunks. A gentle plant or leaf compost works well. Avoid a strong, salty, or coarse material on turf, because it can burn or clump.

For a garden bed, most general composts work. Plant and leaf compost, yard-waste compost, mushroom compost, and composted manure all improve a bed when worked into the soil. Pick a richer compost like composted manure for hungry vegetable beds. Pick a milder one for general beds and borders.

For a raised bed, use compost as part of a blend, not the whole fill. Compost is light and holds no structure alone, so a bed of straight compost sinks and dries out. Mix a general or blended compost with topsoil, using it as a share of the total, often 25 to 50 percent. The soil gives body and the compost gives richness.

Once you have chosen the type, size the job with the calculator. Enter the area and the finished depth for a lawn or bed. For a raised bed, size the bed volume and take the compost share of the blend. Keep the overage allowance on, and order by name so the load fits the place you are using it.