Can I Reuse Old Potting Soil?

Gayla Trail shares what she's learned about reusing potting soil.

Mold Potting

Mold Potting

An easy way to repot your plant is to use a method called “mold potting.” Mold potting involves setting your houseplant (still in its grow pot) in the new container at the appropriate level, and then filling in around the pot with soil.

Photo by: Photo by Lisa Steinkopf

Photo by Lisa Steinkopf

Q: Can I reuse old potting soil?

ANSWER:

When I started out as a container gardener I could not find literature that addressed this issue, the implication being that one would start out fresh each spring. This is fine when we’re talking about a pair of containers flanking the front door, but when containers ARE your garden, and the soil has to be carried up three flights of stairs without an elevator… I threw caution to the wind that second year and have never looked back. Allow me to share what I learned along the way.

Potted soil is not technically soil at all. It is a close approximation of the real deal comprised of lightweight fillers to aid drainage, and organic matter that provides nutrition and water retention. This substitution is necessary as soil from the garden will become compacted in pots and rot your plants’ roots. Nutrients and organic matter leach out of a pot much faster than they do in the ground or a raised bed. By year’s end what’s left in the pot is primarily filler with very little nutrition if any at all.

In the springtime, just before planting:

  • Replenish depleted potted soil with organic matter such as compost or manure. Add no more than 25% organic matter to 75% old soil. Compost is dense, so using too much can lead to that compaction you are trying to avoid. Vermicompost, aka worm poop, is a lightweight, nutritionally balanced additive (approx. equal (N) nitrogen, (P) phosphorous, and (K) potassium) that I prefer for containers. Start a worm bin and make your own!
  • Add more fillers such as coir (coconut husk fiber), grit, or perlite if the mix feels too heavy.
  • Slow-release fertilizers are also good additives that won’t weigh down the mix. I always add kelp meal by the handful to help plants deal with the stresses of container life as well as crushed eggshells, which add both calcium and act as grit, and fishmeal for nitrogen and healthy leaf growth.
  • Diseases can carry over so do use fresh soil with disease-prone crops like tomatoes, or in pots where disease was previously a problem. To avoid spreading disease I practice crop rotation between pots, using the old mix for tough herbs that are better suited to poor soil.

Garden authority Gayla Trail is the creator of YouGrowGirl.com.

Keep Reading

Next Up

Growing Veggies? Check Soil’s Drainage and Composition

Whether your veggie garden will be a bounty or a bust depends in large part on the quality of its soil. Learn how to check your soil in this HGTV feature.

Growing Veggies? Test for Nutrients, pH Levels, Toxins

Getting ready to plant your vegetable garden? You'll want to test your vegetable garden soil for nutrients, soil pH levels and the presence of toxins.

How to Amend Garden Soil

Tips for turning less than ideal soil into a planting-rich medium.

Using Coffee Grounds in the Garden

Learn how to give your plants a pick-me-up using leftover grounds from your morning brew.

When Is it Time to Plant?

Eager to plant, but aren't sure when to start? The answer lies in your soil.

Design a Shade Garden With Carolyne Roehm

Get tips for designing a shade garden from lifestyle expert Carolyne Roehm.

Save Money on Your Veggies: Grow From Seed

Build up your veggie-growing skills: Besides the flavor, you'll love the economics.

Veggies You Can Start From Seed and Veggies You Can’t

Nearly any plant can be started from a seed, but in vegetable gardening starting from seeds may not be the best plan.

Shade Garden Designs

Celebrate shade and all the magic it brings to a yard by filling it with a beautiful garden design. We’ll show you how.

Planting Pumpkin Seeds

Learn how to plant pumpkin seeds with our expert advice—and you can grow your own pumpkins for pennies a pound.

On TV

Log Cabin Living

6:30am | 5:30c

Log Cabin Living

7:30am | 6:30c

Desert Flippers

12:30pm | 11:30c

Desert Flippers

1:30pm | 12:30c

Desert Flippers

2:30pm | 1:30c

Desert Flippers

3:30pm | 2:30c

Flip or Flop

4:30pm | 3:30c

Flip or Flop

5:30pm | 4:30c

Flip or Flop

6:30pm | 5:30c

Flip or Flop

7:30pm | 6:30c
On Tonight
On Tonight

Flip or Flop

8pm | 7c

Flip or Flop

8:30pm | 7:30c

Flip or Flop Atlanta

9:30pm | 8:30c

House Hunters

10pm | 9c

House Hunters

11pm | 10c

House Hunters

11:30pm | 10:30c

Flip or Flop Atlanta

12:30am | 11:30c

House Hunters

1am | 12c

House Hunters

2:30am | 1:30c

Flip or Flop

3:30am | 2:30c

Follow Us Everywhere

Join the party! Don't miss HGTV in your favorite social media feeds.