Composting is a gardener’s form of magic. It has the power to transform vegetable peelings into nutrient-rich soil and help plants grow. It’s also relatively simple to do, despite the complex processes that go into making it happen.
There’s no shortage of options for using the precious results. A more common problem is that there’s rarely enough compost to go around. That makes what you do with it all the more important.
We asked our gardening community how they like to use their compost. The answers are varied—and that’s what we love about them. Not only is compost easy to make, it’s incredibly versatile.
What does finished compost look like?
Before you raid your compost bin, remember that using compost before it’s ready can attract pests and damage garden plants. It can also use up nutrients in your soil, making these same nutrients unavailable to your garden plants.
To make sure that your compost is ready to use, grab a handful and have a look. Mature compost has the following characteristics:
- A texture that’s crumbly and smooth. Depending on what you add to your pile, there may also be woody or fibrous pieces. But there shouldn’t be anything recognizable—like intact peelings or leaves. A few avocado pits or corncobs are normal, since these take longer to break down. Remove them from your finished compost and return to the pile to break down further.
- A smell that’s sweetly fragrant and loamy, like a forest on a wet day. Traces of ammonia or sour odors indicate your compost needs more time to mature.
- A dark, rich color. They don’t call it ‘black gold’ for nothing.
When mature, your compost pile will be reduced by about one third of its original amount. The overall temperature of the pile will be within 10 F of the temperature outside. (A pile that’s hot in the center means it’s still working.) If you’re still not sure if your compost is ready, there are tests you can perform to be sure.
The University of Florida offers this simple germination test involving radish seeds—some of the quickest seeds to sprout. The University of Illinois has an in-depth guide to looking at finished compost.
How long does compost take to mature?
The speed at which organic matter breaks down depends on three things:
- The size and type of organic matter added to your pile. Chopped and shredded material breaks down more quickly than whole material. A correct ratio of brown, carbon-rich ingredients to green, nitrogen-rich ingredients will also speed decomposition.
- How often you turn your pile while it’s composting. Turning a pile improves aeration and helps move larger bits to the center where they will decompose more quickly. A compost tumbler makes this process quick and easy.
- Whether you’re using a hot or cold composting method. Hot composting, while more work to monitor and set up, will break down food waste more quickly than cold. In hot composting, it’s easy to tell when the compost is finished. The temperature of the pile drops and doesn’t heat up again when turned. Hot composts work best with shredded materials and a carbon to nitrogen ration of 30 to 1. Compost tumblers can work as hot composters, because their sealed design helps conserve heat and mix the hot composting matter with new materials.
Depending on the factors above your compost could take anywhere from four weeks to 12 months to fully decompose. If you’re using a tumbler, you’ll have ready-to-use compost in three weeks to three months.
Benefits of using compost in the yard and garden
Once your compost is ready to use, add it to your soil at any time of year to get the following benefits:
- Improved moisture retention: soil fortified with compost holds more water for longer periods. You’ll water your garden less often, saving time and money.
- Better soil structure: more organic matter in your soil means more air pockets for water and nutrients to travel unimpeded.
- Improved nutrient levels: compost is high in the ‘big three’ nutrients needed by garden vegetables—nitrogen, phosphorous, and potassium. It also contains trace elements such as calcium, magnesium, iron, and zinc.
- Balanced soil pH: Adding compost prevents your soil from becoming to acidic or alkaline.
- Healthy natural soil organisms: critters like worms and soldier flies feed on compost ingredients. They also help out your garden.
Don’t worry about burning plants or polluting nearby waters. Finished compost doesn’t come with these risks. But while a few inches of compost is good for your garden, there are ways to get more from your composting efforts.
Top 10 uses for mature compost
1. Use as mulch.
Compost-as-mulch is a fantastic way to boost your garden’s harvest. Naturally absorbent and dense, compost applied to the soil surface will prevent evaporation when laid over drip irrigation or after watering. It will also prevent weeds from sprouting. Apply in a 3 to 6 inch layer and rake until even.
2. Mix DIY potting soil.
Finished compost makes an excellent addition to homemade potting soil. Remove large debris by passing compost through a half- to 1-inch soil screen. Mix in the following proportions:
- 1 part compost
- 1 part vermiculite
- 1 part topsoil
Use in container gardens and when potting up starter plants.
3. Brew compost tea.
Have you ever wondered how to get the benefits of compost directly to your plant’s roots? Steeping your compost in a liquid emulsion is one way to concentrate the nutrients and make them easier to absorb. For a quick and easy recipe, see this primer on making compost tea at home.
4. Feed fall perennials.
Add 2 to 4 cups of compost to the planting hole of fall perennials. This will feed your plants and help extend their bloom time. Tennessee urban garden center Bees on a Bicycle says that “…adding a bit of compost to your digging hole retains moisture and gives the plant a boost for vigorous, healthy growth. Compost is a key factor in regenerative gardening and allows us to proceed without fertilizer leaching into our water table. The healthy soil benefits not only the plant, but vital organisms that help our ecosystem.”
5. Feed spring bulbs.
Now is also the time to plant your bulbs for springtime. Add compost to the planting hole to help bulbs that have recently been divided. This will give them an added boost when they come out of winter dormancy.
6. Spread on new or established lawns.
Fall brings about the best weather for planting and maintaining lawns. Add a one- to two-inch layer of compost on top of your lawn in the weeks before planting. This will improve the tilth of your soil and provide the nutrients your seeds need to thrive.
7. Top dress garden beds.
Twice each year we give our raised beds a hearty dose of finished compost. We sprinkle it along the soil surface, and soon seasonal rains wash the nutrients down to root level. Worms do the rest of the work, pulling the organic matter into the soil. And we’re not alone. Southern Harvest Farms in Georgia recently shared how adding compost to their garden beds has increased water absorption and improved runoff.
8. Add to fruit trees.
Fruit trees are best fertilized in early spring before buds open. Be sure to reserve some of your finished compost for the growing season if you generally harvest in the fall. If you miss this window, applying compost between March and July will still give your trees a boost. You can also use as mulch any time of year. Compost is high in nitrogen—a fruit-tree favorite—along with many micro and macronutrients.
9. Feed container plants.
When you freshen up the soil around your outdoor potted plants or transfer to bigger pots, add screened compost to boost growth. Mix with potting soil and/or peat moss for better absorption.
10. Grow melons, tomatoes, eggplant, cucumbers, and squash.
These heavy feeders need lots of nitrogen to produce. That’s why it’s not uncommon to see squash plants thriving directly in a compost pile voluntarily. Add compost to the planting holes when transplanting seedlings into the garden. Top dress a few times during the growing season for best results. For a great illustration on how compost helps boost plant growth, check out this Instagram post from Kristi.
More on using finished compost in the yard and garden
Where can I use compost that isn’t fully finished?
Unfinished compost is safe to use when mulching around trees and shrubs. As the compost decomposes, it will add more organic matter to the soil and improve moisture retention.
What about bokashi or foodcycled compost? Is that considered ‘finished’?
Bokashi is a Japanese method of fermenting food waste that involves layering a starter ‘bran’ with your compost in a bucket. The resulting mixture is more of a pickle than compost. It’s not mature or finished until you bury it under a layer of soil where composting can take place.
Food-cycled compost is shredded and dehydrated food waste that works just like organic fertilizer in your garden. Dig in around plants or inside beds to add nutrients to the soil.
Do I need to shred what I put in my compost?
You don’t have to shred what you put into your compost, but chopping and shredding will help speed up the composting process. That’s because smaller pieces mean more surface area. And more surface area means quicker decomposition.
I just started composting for the first time. How long until my compost is ready?
That all depends! What are you composting? What ratio of greens to browns did you add to your compost bin? Are you using a compost tumbler or turning your pile frequently? All these factors will affect the time your compost takes to fully break down. In general, composting takes anywhere from three weeks to one year.
Get started today
Do you have other uses for finished compost? Share with us in the comments below. We’d love to hear from you!
If you’re ready to make the leap into composting, visit our product page for the best composters on the market.