I made beautiful black compost. Then I stared at it for a month wondering what to do with it. I knew compost was good. I did not know how much to use or where to put it. Some plants want more. Some want less. Using it wrong can actually hurt plants.
Here is how to use compost in your garden the right way.
How Much Compost to Use
Compost is powerful. A little goes a long way. For most garden applications, one to two inches is plenty. More than three inches can overload the soil with nutrients and harm plants.
Think of compost like vitamins, not food. You would not take a whole bottle of vitamins at once. You take one per day. Compost works the same way. A moderate amount feeds the soil for months. Too much throws everything out of balance.
7 Ways to Use Compost in Your Garden
1. Soil Amendment for New Beds
Spread 2 to 3 inches of compost over the soil surface. Till or dig it into the top 6 to 8 inches. This improves drainage in clay soil and water retention in sandy soil. Do this a few weeks before planting so the compost settles into the soil.
I use about one cubic yard of compost per 300 square feet of new garden bed. That works out to roughly a 2-inch layer.
2. Top-Dressing Existing Beds
Spread a half inch to one inch of compost on top of the soil around existing plants. Do not dig it in. That would damage roots. Just spread it on the surface. Water it in. Earthworms will pull the compost down into the soil over time.
I top-dress my vegetable garden every spring before planting. It takes about 30 minutes for my 200 square foot garden.
3. Compost Tea
Compost tea is liquid fertilizer made by soaking compost in water. Fill a bucket one-third with compost. Top off with water. Let it steep for three to five days. Stir once per day. Strain out the solids. Use the liquid to water plants.
Compost tea gives plants a quick nutrient boost. It does not replace soil compost. It is a supplement, not the main meal. I use compost tea on heavy feeders like tomatoes and squash every two weeks during the growing season.
4. Seed Starting Mix
Mix one part compost with two parts potting soil for a rich seed starting mix. Do not use pure compost for seed starting. It is too heavy and may contain microbes that cause damping off disease.
I screen my compost through a half-inch mesh before using it for seed starting. This removes chunks that would block tiny seedlings.
5. Lawn Top-Dressing
Spread a quarter to half inch of compost over your lawn. Use a shovel to scatter small piles. Rake it smooth. The compost filters down through the grass and feeds the soil from the top.
This is best done after aeration. The compost fills the aeration holes and gets organic matter deep into the root zone. I top-dress my lawn with compost every spring.
6. Mulch Around Trees and Shrubs
Spread a one to two inch layer of compost around the base of trees and shrubs. Keep it a few inches away from the trunk. Compost piled against the trunk causes rot.
Compost mulch feeds the soil as it breaks down. It also suppresses weeds and holds moisture. I apply compost around my fruit trees every spring.
7. Potting Mix Booster
Add one part compost to three parts potting soil for container plants. The compost adds nutrients that potting soil lacks. It also improves water retention so containers do not dry out as fast.
Do not use more than 25% compost in containers. Too much compost in a pot compacts over time and suffocates roots.
When to Apply Compost
| Application | Best Time | How Much |
|---|---|---|
| New garden beds | Fall or early spring | 2-3 inches tilled in |
| Existing beds | Spring | 0.5-1 inch top-dressed |
| Lawns | Spring or fall | 0.25-0.5 inch |
| Trees and shrubs | Spring | 1-2 inches as mulch |
Frequently Asked Questions
Can you use too much compost?
Yes. More than three inches of compost can overload soil with phosphorus and potassium. This causes nutrient imbalances. Stick to one to two inches. Compost is concentrated. More is not better.
Should I till compost into the soil or leave it on top?
For new beds, till compost into the top six inches. For existing beds with plants, leave it on top as a mulch. Tilling around established plants damages roots. The compost works its way down naturally over time.
Can I use unfinished compost?
No. Unfinished compost steals nitrogen from the soil as it continues breaking down. This starves your plants. Only use compost that is dark, crumbly, and smells earthy. If you can still recognize the original materials, it needs more time.
