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How to Rejuvenate Potting Soil

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Avid container gardeners are acutely aware of two facts: potting soil becomes depleted over time, and continually replacing it gets expensive. Old potting soil lacks nutrients, is not properly aerated and can cause drainage problems for plants, ultimately forming a brick of dirt that harms plants rather than helps them. Fortunately, rejuvenating old potting soil is easy and inexpensive and gives you an excuse to go outside and play in the dirt.

Place the potting soil on a large tarp, and use a garden rake to break up any clumps. Remove any rocks, root pieces or other debris that is present in the soil.

Scoop the soil into a large bucket with holes in the bottom. Fill the bucket with water, and allow it to drain out the bottom. Do this twice, and then spread the soil back out onto the tarp and allow it to dry.

Sift store-brought compost through a 1/2-inch screen, and mix it with the soil you are rejuvenating. Add as much compost as you have depleted potting soil so that you have a 50/50 mix of old potting soil and new compost when you are finished. For an alternative that makes a bit less soil, mix perlite and screened compost into the depleted soil, adding 1/4 pound of each for each pound of depleted potting soil. You can transfer the soil into a large bucket or wheelbarrow if you find it easier to mix the soil in a container rather than on the tarp.

Mix in a light dusting of lime and gypsum and 1 tablespoon of slow-release fertilizer for every gallon of soil you have.

Moisten the soil mix lightly, and shovel it into a large plastic storage bin. Allow it to cure in the bin for two weeks before using.

Things Needed
  • Large tarp
  • Garden rake
  • Large bucket with holes in the bottom
  • Shovel
  • 1/2-inch screen
  • Store-bought compost
  • Perlite (optional)
  • Wheelbarrow (optional)
  • Lime (optional)
  • Gypsum
  • Slow-release fertilizer
  • Large plastic storage tub
Warnings
  • Avoid using homemade compost unless you are a very experienced composter and gardener. Homemade compost often harbors diseases and weed seeds.
  • Seal any used potting soil that has hosted insects, diseases or fungal infections in a plastic bag and discard it. Diseases and insects can sustain themselves in potting soil for a long time, and it is best to simply start with new soil rather than try to fix soil with these problems.
References
  • Oregon Live LLC: Rejuvenate Potting Soil
  • Maine Organic Farmers and Gardeners Association: The Dirt on Potting Soil
Photo Credits
  • Jupiterimages/Photos.com/Getty Images
About the Author

Writing professionally since 2008, Michelle Miley specializes in home and garden topics but frequently pens career, style and marketing pieces. Her essays have been used on college entrance exams and she has more than 4,000 publishing credits. She holds an Associate of Applied Science in accounting, having graduated summa cum laude.

How to Rejuvenate Potting Soil. Avid container gardeners are acutely aware of two facts: potting soil becomes depleted over time, and continually replacing it gets expensive. Old potting soil lacks nutrients, is not properly aerated and can cause drainage problems for plants, ultimately forming a brick of dirt that …

GARDENING AUSTRALIA

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Rejuvenating Potting Mix

SERIES 27 | Episode 19

What to do when you have a heavy container full of spent potting mix, but don’t want to have to re-pot the whole plant or tip out the contents.

HOW TO . RESCUE A POT OF USED-UP POTTING MIX

For a large pot – around half a square metre in area – add

  • A 50mm thick layer of fine compost
  • A handful of complete dry or pelletised organic fertiliser
  • Drench with enough liquid, organic fertiliser to thoroughly wet the entire pot

Transcript

Josh Byrne

JOSH BYRNE: I reckon a couple of productive pots by the back door are a great addition to any household.

Here’s one that’s ready to replant, so I’m pulling out the old, tired lettuce, the roots too.

The potting mix is pretty tired, also but don’t chuck it out – you can rejuvenate it.

Potting mix like this is made up of structural components, like pine bark and coir, which is slow to break down. They give the whole thing body, aeration and good drainage. It also contains compost and fertiliser and this is the stuff that gets used up and the part that we have to replace before replanting.

First, I’m adding fine compost to about 50mm thick. Then a generous handful of complete organic fertiliser, which is enough for this 0.5 square metre surface area of pot. And then I’m mixing it through thoroughly.

Lastly, a good drenching with liquid organic fertiliser for nutrients and organic fines, and you can consider this potting mix rejuvenated and ready for replanting.

Josh shows how to put life back into potting mix