If you garden, chances are that you have old potting soil sitting around. It seems like a shame to throw it out, but pause before you put it back in your garden! There are a few things you should know before you plant new seedlings in old potting soil.
While there are many ways to reuse old potting soil in your garden, there are some risks that go along with it, too. In this article, we’ll discuss everything you need to know to answer the question: Can I use old potting soil in the ground around my garden?
- Reusing Potting Soil For Vegetable Beds
- Using Old Potting Soil on Flower Beds and Borders
- Using Old Potting Soil On Lawns
- Putting Old Potting Soil in Compost Bin
- Using Old Potting Soil to Fill Holes in Your Yard
Using Old Potting Soil in the Ground Around My Garden?
You can use old potting soil in the ground in your garden, but there are a couple of caveats. First, remember that potting soil is intended to be used in containers. It is not the same as garden soil, so you will need to mix the two components.
You should also revitalize your old potting soil before adding it to a new bed. If you skip this step, your plants will suffer for it. Old potting soil has lost not only some of its nutrients but also its draining ability, which will affect your plants’ ability to get water.
One of the best and safest ways to use old potting soil around your yard is to use it to “bulk up” fresh soil or compost. This lets you stretch the nutrient-rich material further while avoiding waste. It will also save you money, as buying new potting soil every season can quickly become expensive.
Reusing Potting Soil For Vegetable Beds
Gardeners do not usually use potting soil in vegetable beds. If you decide to use it, mix it with regular soil to ensure that your vegetable beds get the nutrition and aeration they need to thrive. Also bear in mind that there is a difference, though a small one, between potting soil and raised bed soil.
Before reusing old potting soil in vegetable beds, make sure to reinvigorate it with fresh organic matter and also to sterilize the soil. This will ensure that it has the proper nutrients and doesn’t transfer any bacteria from the last growing season, which can impede the growth of your vegetables.
Many gardeners use old potting soil as a foundation for new beds. This helps you save on soil costs and recycle already-used material. Meanwhile, with healthy new soil on top, your plants will have all the nutrients they need to thrive. You can also simply mix old soil and new soil to improve drainage, nutrient content, and aeration.
Using Old Potting Soil on Flower Beds and Borders
If you are sure that your old potting soil is free of harmful bacteria, you can use it in flower beds and borders. But make sure you mix it with other soil that is formulated for raised beds or outdoor plants. This will help replenish the nutrients in the old soil as well as reconfigure it for outdoor use.
Many gardeners reuse old potting soil as a “foundation” for their garden beds, then fill in the top with fresh soil. This is a great way to reuse the soil without needing to mix it or worry about poor drainage.
Using Old Potting Soil On Lawns
If you want to reseed or topdress your lawn, potting soil can be an excellent choice. Topdressing involves spreading a layer of soil over the lawn so that it breaks down and fertilizes the grass. However, old potting soil might not have enough nutrients to be effective.
A good way to get around this is to mix the old potting soil with compost. Since many gardeners use compost as a rule for reseeding or topdressing, it is easy simply to mix the soil and compost to avoid waste and stretch the material as far as possible.
After just a few days, the soil will start to sink into the ground, especially if you have had rain. The whole goal of this is to fertilize the ground, so while you can use old potting soil, you need to make sure it has been mixed with nutrient-rich soil or compost or otherwise revitalized.
Putting Old Potting Soil in Compost Bin
Putting old potting soil in your compost bin is an excellent way to enrich the compost and avoid wasting the depleted soil. However, it is important not to throw it in as is. Used potting soil can contain harmful bacteria that might spread throughout the compost pile and infect plants that come in contact with it.
Thankfully, it is simple to sterilize potting soil to kill any harbored bacteria. Put it into a black garbage bag and lay it out in a sunny spot. The trapped heat will kill off bacteria. After a week, the soil will be safe to add to your compost.
For the same reason, make sure you never throw old, diseased plants into the compost pile. Compost is the perfect environment for bacteria to multiply, so a single diseased plant can ruin the entire thing. Always throw away diseased plants to avoid spreading bacteria or fungus.
Using Old Potting Soil to Fill Holes in Your Yard
Using old potting soil to fill holes in your yard is a great way to use up that material. But you should not rely on potting soil by itself. Instead, mix it with equal parts sand and compost. This will provide material that is thick enough and nutritious enough to support grass and weight.
When filling the hole, use equal parts of soil, sand, and compost and go layer by layer. Between each layer, tamp it down firmly. Continue to add layers until the top of the hole is a few inches below the rest of the level ground.
Eventually, the ground will even out as elements shift and plant roots spread. It may take a couple of seasons to be fully level, but it will happen eventually. Fill the hole properly and be patient. If it isn’t successful after a few seasons, repeat the process.
Risks of Reusing Old Potting Soil in Your Garden
There are three major risks of reusing old potting soil in your garden: lack of nutrients, draining ability, and disease transfer. As soil ages, it loses its nutrient content, especially if it has already hosted plants. New plants may not be able to get the important minerals they need to thrive.
Soil also loses its ability to drain effectively. That means it becomes easier to overwater your plants, which can cause many problems. Lastly, unsterilized potting soil can transfer harmful bacteria from old plants. The good news is that there are solutions to each of these issues.
Can I Reuse Potting Soil from a Dead Plant?
If you have a container plant that has died, you might be able to reuse the potting soil. If the plant died from lack of care or unfavorable conditions (too much water, not enough light, and so forth), you are probably safe to reuse the potting soil as is.
However, if the old plant died because it was infected, do not reuse the potting soil. At the very least, sterilize it before reusing it. It is always a good idea to replenish the mineral content when using recycled soil, which you can usually do by mixing it with new soil, compost, or other plant food.
The same rule goes for pests. If your plants died because of an insect infestation, the soil isn’t safe to reuse. Many pests lay eggs in the soil, and these can survive the winter before hatching. Don’t store old potting soil over the winter and assume it is safe to use next spring!
How to Reuse Your Potting Soil Safely
Before reusing your old potting soil, you need to do two things: sterilize and revitalize. Sterilizing kills the old bacteria and ensures that there is no disease transferral from plants that were grown previously. Revitalizing replenishes the nutrients in the soil that support healthy plant growth.
To sterilize your old potting soil, put it into black garbage bags and let it lay in the sun for a week to trap heat. To revitalize it, mix it with fresh soil or potting mix. This will help build up the proper density and nutrients that your plant needs to grow well.
Some gardeners even suggest that you microwave old potting soil to kill the bacteria. Surprisingly, this can be an effective way to sterilize it. While it is much quicker than the garbage bag method, it is more labor-intensive, since you can only microwave about one pound of soil at a time.
Sterilizing, solarizing, and revitalizing old potting soil is a lot of work but is a great way to use up spent soil. It is up to you to decide if the effort is worth it for your needs.
How to Dispose of Old Potting Soil
How you dispose of old potting soil depends on the state of the soil. If there is any chance that it could harbor disease, throw it away rather than risking the bacteria spreading to other parts of your garden. However, if it is safe, you can dispose of it in your compost pile.
Alternatively, you can, as we have discussed in this article, replenish your soil’s nutrients and redistribute it around your yard. There are pros and cons to both options and ultimately, if you are unsure about the state of the soil, you should throw it away to avoid hurting other plants.
Can I Put Old Compost in My Green Bin?
Some cities use three colored bins to designate household, reusable, and compostable waste. If you have old compost that has been sitting undisturbed for several seasons, it is not a good idea to put it in your green bin. That’s because once compost breaks down, it becomes, essentially, dirt.
Many cities specify that you should not throw dirt away in a green bin. The best option is to spread it around your yard to use those leftover nutrients on your garden beds or grass. It is likely to degrade within just a few days and will no longer be noticeable.
How Often Should You Change Compost in Pots?
If you are using compost to grow a plant in a pot, make sure you change it every year or two. There is no hard and fast rule for this — simply a range that should help you judge when the nutrients in the soil are depleted.
Changing the compost will also improve the drainage and aeration in the pot, both of which are vital for healthy plant growth. Potted plants tend to deplete the soil nutrients more quickly than plants in raised beds. If you have a particularly fast-growing plant, consider changing the compost every year in the spring.
Can I Use Old Compost For Bulbs?
Bulbs are an excellent way to use up compost that has been sitting for a season or two. This is because bulbs don’t have high nutritional needs and many of them need almost no fertilizer. If you have old compost that has deteriorated, mix it with a bit of plant food for bulbs.
Make sure you research before planting because not all bulbs have the same nutritional needs. While many of them don’t need nutrient supplementation, some types do. You can also combine old compost with fresh garden soil to increase the nutrient load for your bulbs.
If you are wondering: “Can I use old potting soil in the ground around my garden?” the answer is yes, but there are a few steps to take first. There is no reason to throw that old soil out unless you suspect that it is diseased.
In most cases, sterilizing and revitalizing potting soil puts it back in shape to nourish your plants. If you are willing to put in the time and effort, you can cut back on cost and waste by revamping your old potting soil for new uses in and around your garden.