Set the pot in a shallow container of water (if size allows), allowing the soil to slowly absorb the water. This technique is known as bottom watering. It may take an hour or more to thoroughly re-wet the soil. Be careful not to leave pots soaking in standing water continuously.
Since potting soil does lose nutrients as it's used, Charlotte Ekker Wiggins, an author and Master Gardener, recommends mixing old soil with new soil to refresh it before reusing. “One of the easiest ways to reuse potting soil is to add it to existing flower beds and compost bins.
Add Nutrients and Beneficial Microbes to Old Soil
Here are some ways you can add nutrients and organic matter to soil: Add a handful of a slow release fertilizer like manure. Mix in one part compost for every three or four parts of the old potting mix. Apply a liquid fertilizer like compost tea every two weeks.
To revamp your potting mix, you'll need:
Compost to boost microbial life. Perlite to add air and structure. Fertiliser (preferably organic pellets) to up the nutrients. Lime or dolomite to raise the pH.
Fortunately, most potting soil can last up to two years because that is the lifespan of the peat moss it likely contains. (Tip: To keep it as fresh as possible, store it sealed in its original bag or another covered container in a climate-controlled environment.)
Compost recharges and adds incredible structure the soil. The finer the compost is, the better for potting soil. Next, add in the worms castings. As for how much to add, 2 to 3 cups of castings for every 5 gallon bucket of old potting soil is a good rule of thumb.
If your old potting soil was a victim of pests or disease it is best not to reuse it. After that, check the soil level in each pot. Depending on what each plant went through, it will need to get topped up. You can do that with perlite, lime, or gypsum - they last longer, and you won't need a new potting mix.
If you notice a rotten egg smell coming from your potting soil, it's a sign that it's gone bad. The bad smell is caused by bacteria and fungi that are breaking down the organic matter in the soil. It still can be used if you spread it out on a tarp and let it bask in the sun.
After a long dry period the earth becomes dehydrated. From dry weather or lack of watering, if soil is dead and lacks important organic ingredients it will actually repel water, rather than it soaking in when it rains or water is applied. This is known as 'Hydrophobic Soil'.
Large outdoor planters and containers require large quantities of potting mix, and yes, the same mix can be reused from year to year. Begin with a good-quality mix like Miracle-Gro Potting Mix or a mix recommended by locally owned garden centers.
3. How Long Can You Store Potting Soil? Opened bags of new potting soil can retain quality for around 6 to 12 months. For unopened and unused potting soil, you can store it for about a year or two before it goes bad.
Used potting soil may contain pests and pathogens.
Another good reason to not reuse old potting soil? The potential for pests and plant diseases. If plants from a previous season had any insect infestations, throwing out the plants probably isn't enough.
For general garden start-up, mix one cup of Epsom salts per 100 square feet into soil before planting. To boost germination, mix one tablespoon of Epsom salts in a gallon of water and add to soil after seeding.
Potting soil vs. potting mix: Though these terms are used interchangeably, there is a difference. Potting soil may or may not contain soil, while potting mix is strictly a soilless medium. Potting mix is sterile, which makes it safer for plants because it doesn't contain pathogens such as fungus or other diseases.
Hydrophobic soil occurs when a waxy residue builds up on the soil particles resulting in it repelling water rather than absorbing it. It is most common in sandy soils, dried out potting mix and soils containing unrotted organic matter. You can identify hydrophobic soil by watering it.
Can you reuse soil with root rot? We recommend sterilizing the soil before reusing the soil. This will ensure there were no diseases or fungus that were growing in the soil while the roots were rotting. Once the soil is sterilized, mix with new potting soil 50/50.
Plants typically benefit from being repotted every 12 to 18 months, depending on how actively they are growing. Some slow growers, like cacti, can call the same pot home for years, but will just require a soil replenishment.
Make sure the potting soil is completely dry, as any lingering moisture can cause a variety of mold or mildew problems over the winter. 2.) Find or buy a large plastic storage tub. I get mine from my local home improvement store — 20- or 30-gallon sizes with lids work well, and they range from $7.00 – $12.00 each.
If plants died from bacterial, fungal or viral disease, then you definitely do not want to reuse the soil, as soilborne pathogens can still be present and active. However, if the plants that grew in the soil before were healthy, it is generally OK to reuse the potting soil.
Rejuvenating Used Potting Soil
Many gardeners simply mix used potting soil with new material, using about half of each, with a few handfuls of organic fertilizer added to boost plant nutrition. Or, you can place the old potting soil in the bottoms of very large containers, and fill the upper parts with a fresh mix.
If it's been awhile, and your plants aren't performing well, maybe it's time you looked into it. Typically, changing the soil in your potted plants should happen every 12 to 18 months. There are some exceptions that may change this timing.
As plant roots grow, they'll gradually displace the soil in the pot. Less soil means that when you do water, most of the water will just drain away, and the roots won't have a chance to actually absorb the water. The soil that does remain will dry out quickly because the roots will absorb any water quickly.