Potting soils often contains peat moss which is valued because it decomposes slowly, is lightweight, and retains water. Paradoxically though, when peat moss dries out it is very difficult to re-wet. Bags of potting soil can even dry out in storage.
If your potting soil has been sitting in your shed since last year in an opened bag and it's gotten wet, toss it. If it somehow stayed bone dry, it should be OK to use.
Set the pot in a shallow container of water, allowing the soil to absorb the water slowly. It may take an hour or more to thoroughly re-wet the soil. Be careful not to leave pots soaking in standing water for more than a couple of hours.
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.
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.
You can improve the water retention properties of your soil by adding vermiculite, sphagnum (peat) moss, and/or coconut coir. When you make the soil retain more moisture, you'll also need to improve the drainage to prevent any watering issues. You can improve the drainage by adding perlite, Leca, and sand to your soil.
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.
If the soil feels dry, it's time to water. In the spring and fall and in cooler climates, it might be sufficient to water container plants every two to three days. In the summer and in warm climates, container plants usually require daily watering, unless they are succulents or other drought-tolerant xeriscape plants.
Organic Potting Mix
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.
Adding high-quality organic compost can help improve the quality of old potting soil. Fertilizers are also an excellent way to revive old potting soil and can provide much needed nutrients.
3 ways to restore weary soil
Barely moist is all you need. Its easier to moisten dry soil by first clearing the area you want to plant. Slash/ cut everything down leaving those all important roots in play. Leave any useful up and coming seedlings, or plants in their prime, and work around them.
Having a dry soil is something you want to avoid as this can result in withered or dead plants. When the dry season arrives, soil that lacks organic ingredients will quickly become dehydrated and will actually repel water instead of absorbing it.
As long as used potting soil still looks fairly fluffy and doesn't emit a rotten odor, gardeners should be able to use it again with good results. However, if the plants formerly grown in the potting soil struggled with disease or insect problems, it's probably best to discard the mix and start fresh next season.
However, all is not lost just because your potting soil has celebrated its second anniversary. “If your potting soil has passed the two-year mark, you can still make use out of it by amending it or adding it to raised beds for support or sprinkling it on flower beds,” says Sears.
Last year's potting soil may look ready to re-use, but odds are much of the nutritional value leached away on its first go around. Replenish lost nutrients by adding slow-release fertilizers, vermiculite or compost.
There are two causes for root rot, but the main cause is poorly drained or overwatered soils. These soggy conditions prevent roots from absorbing all the oxygen they require to live. As the oxygen-starved roots die and decay, their rot can spread to healthier roots, even if the soggy conditions have been rectified.
“If soil is left too wet for too long, it can cause root rot,” Marino says. “That's what we call over watering. On the other hand, if your plant's soil is consistently too dry you're likely under watering. Letting your soil dry out before watering is key for plants to receive the perfect balance of water and oxygen.”
Too little water causes a plant to lose turgor, the rigidity in cells and tissues. There are some diseases that can trigger wilting, but the easiest and most likely explanation is under watering. Dry soil. If the soil around a plant is dry, it may need more water.
Water Well. Water thoroughly after repotting to help the soil settle around your plant's roots. Plenty of moisture will also help your plant recover from the move better.
One of the most frequent issues plant owners have is overwatering. After watering, the soil around the plant should remain moist for a while to allow the plant to receive the nutrients and water it needs. 2 to 4 hours after watering, the soil should still be moist.
Peat helps soil retain water. Use a blend that provides the right combination of drainage and water retention for healthy growth. If your containers seem to need water multiple times throughout the day, consider a water retaining soil additive. These products soak up water then release it slowly back into the soil.
Gardening FAQ
The problem with your soil resisting hydration is not uncommon. It usually begins with the soil being watered incompletely and then drying more than it should. After that it can become hydrophobic and actually repel water! The ingredient in the soil that is causing that problem is peat.
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.