Peat Alternatives: One Gardener’s Experience

Like many gardeners, I’m concerned about the depletion of peat resources around the world. The main ingredient in many potting mixes, peat comes from slow-forming peat bogs. It takes generations for the peat to form and the bogs are home to diverse plants and animals. Helping preserve those bogs is why I tried two peat alternatives in my container plantings this past summer—with mixed results. Here’s what I tried, how it went and what I’ll be doing going forward.

One caveat: This is just one gardener’s experience. Please let us know in the comments whether you have tried peat alternatives and what works for you.

Two Peat Alternatives

Most peat alternatives on the market include either processed wood products or coconut coir to replace peat. In potting mix, peat retains water, creates air pockets and helps plants access nutrients. Other common ingredients in potting mix are perlite or vermiculite, which lighten the mix and improve drainage, and fertilizers, such as poultry litter, manure, compost or bat guano.

For my experiments, I made my own potting mix using coconut coir and also bought a commercial mix that included mostly refined forest products in additional to fertilizers, perlite and a small amount of peat. Other completely peat-free commercial options are available but tend to be expensive.

For the coco coir mix, I bought coco coir bricks at the local pet store. (The product is used as bedding materials for lizards.) You mix the bricks with lots of water to fluff them up. Then I added fertilizers and perlite. For seed starting, the mix was two parts coco coir, two parts perlite and one part earthworm castings. For my outdoor containers, it was equal parts coco coir and perlite and about half as much processed cow manure.

As a seed starter, the coco coir mix worked well but it required more frequent watering than standard peat-based seed starting mixes. As a potting mix, the homemade version performed significantly better than the commercial wood-based mixture.

Comparison and Results

With both peat alternatives, I had problems. For instance, one type of tomato (Cherry Falls patio tomato) got a weird leaf disease on plants grown in both the homemade mix and the commercial mix. I’m still not completely sure what caused the issue but a fellow gardener commented that it might be a mineral deficiency. So, I fertilized both of the plants with a tomato fertilizer. The one in the commercial mix died but the one in the homemade mix recovered and went on to produce dozens of cherry tomatoes.

I also had problems with a new petchoa plant I was given to test. Petchoa is a hybrid of petunias and calibrachoa. In both the homemade and the commercial mix, my test plants really struggled. They didn’t grow large or spread much, and the flowers dropped off quickly. I mentioned this to a representative of the plant company and she graciously gave me three more plants to try. I put them in regular peat-based potting mix on my deck in August and as I write this in late October, they are still thriving.

Overall, plants ranging from begonias to hot peppers seemed to grow better in the homemade mix, which I attribute to the large amount of manure in the mix. That said, many of my plants struggled this year. Was it the mix? The drought? Less sun? I’m not entirely sure.

What Happens Next?

Most years, I save my potting mix to use again. (Only the mix with really root-bound plants get tossed.) We moved in 2022, which is why I needed so much potting mix this year. For 2024, I plan to save both the coco-coir mix and the commercial mix and mix them together. Come spring, I’ll add lots of compost to the mix and I may add a bit more perlite or vermiculite, too, to keep the mixes light. We’ll see how things go with the hybrid mix.

Here are a few things I learned from this experiment:

• If you are using peat alternatives, expect to water more. Both the wood mix and the coco coir mix dried out quickly. This may have been exacerbated by the drought this year, but I think they just don’t hold moisture as well as peat does.
• Pay attention to your fertilizers. These mixes may have a different set of micronutrients than peat does. Be sure to give your plants lots of compost or regular doses of fertilizer to keep them growing.
• Going peat-free can be pricy. One reason I made my own mix was that some of the peat-free alternatives were very expensive.
• Making your own is a good option. Price aside, making your own potting mix is worth considering in order to know what is in it. If you have lots of leaves, make leaf mold to use in potting mixes or add a heftier amount of compost to your mix.
• We need much more research. When I talked with the plant company rep about my poor petchoas, she seemed intrigued that I was using peat alternatives. Plant companies and universities have the scale and systems to conduct more research on this issue. I’m sure they will, but in the meantime, I’ll be conducting my own experiments at home.

For more on peat alternatives, check out Gail Brown Hudson’s article in the Spring 2023 issue of Northern Gardener.

Mary Lahr Schier is a longtime Minnesota garden writer and speaker. Follow her on Instagram at @mynortherngarden_mary.