Despite the name, potting soil isn’t soil! Potting mixes are composed of elements that retain moisture, maintain aeration, and provide essential nutrients to container-grown plants. While they mimic natural functions, potting mixes are quite different from natural soils, which are diverse, layered, and living.

A major component of many potting mixes is peat moss. However, harvesting peat is an unsustainable practice, and peat use should be reduced when possible. In this post, I’ll spotlight substitutions you can make to reduce peat use when growing potted plants.

A northern Minnesota peat bog in fall color. — A typical peat bog of northern Minnesota. Note the succession from sedges and grasses around the shoreline to tamarack and spruce forest. The understory is composed of bog-specific shrubs. All are growing on a nearly continuous mat of sphagnum peat moss.

What is peat moss?

Peat moss, often just called peat, is decomposed sphagnum moss. Sphagnum is a mat-forming moss that grows in wet, low-nutrient bogs, called peat bogs. These peat bogs are carbon storage powerhouses, containing nearly 25% of worldwide soil carbon. That’s more carbon stored than all the world’s forests combined!

Harvesting peat has catastrophic environmental impacts. The process requires draining peatlands and excavating the dried sphagnum moss. This destroys the peat bog and begins releasing the once-trapped carbon into the atmosphere. A 2020 study published in Nature calculated that damaged peatlands release about two billion tons of carbon dioxide each year.

What’s more, draining bogs and harvesting the peat destroys the unique ecosystem. Peat bogs are wet, cold, and low in nutrients. Many species can’t survive these conditions, but an entire ecosystem of species can only live in bog conditions. Peat bogs house a biodiverse collection of orchids, mosses, trees, and shrubs that are adapted to thrive in boggy conditions. Draining peatlands destroys these rare, ancient ecosystems, and full restoration isn’t possible.

An example of the dried sphagnum moss products commonly sold in large garden centers.

Peat moss is used in potting mixes because it retains water and is naturally acidic. Peat is also used to create biodegradable pots and containers. However, peat is also prone to problems. When peat moss dries out, it compacts and becomes hydrophobic, or resistant to absorbing water. This makes it difficult for plant roots to remain moist. Peat is also low in nutrients, and peat potting mixes must include nutrient amendments to support plant growth.

No matter how you slice it, peat moss is unsustainable for use in potted plants. But there are better alternatives!

Alternatives to Peat Potting Soils

Gardeners looking for peat alternatives can blend several components to create peat-free or low-peat potting mixes. You can also find pre-mixed potting soils that are peat-free or formulated to be lower in peat. Reducing peat use is the goal, so choose the option that works for you and be open to variation as you learn from growing experience.

Coconut coir

Coconut coir is often recommended as an alternative to peat moss in potting soils. Coir is fiber from the coconut husk. It is a byproduct of coconut processing and is otherwise treated as a waste product.

Like peat, coir can absorb massive amounts of water, up to 10 times its own weight! Coir is also low in nutrients, and is less acidic than peat. It is sold in dried bricks, discs or bales. These coir bricks can be rehydrated and mixed with amendments for nutrition and drainage to create a peat-free potting soil. Commercial peat-free potting mixes with coir are also available.

While coir production is less environmentally damaging than peat, it requires heavy processing and water use. Shipping coir can also incur a large carbon footprint, with nearly all coir sourced from Southeast Asia.

Coir can also retain too much moisture for some seedlings. Native plants adapted to dry soils, like many prairie plants, may not grow well in coir-heavy potting soil. Seedlings may experience root rot. Consider mixing your own potting soil to customize the ratios according to plant needs.

Hennepin County Master Gardeners recommend the following recipe for a peat-free seedling potting mix:

1 part compost
2 parts coconut coir
1 part builder’s (coarse) sand

When starting native plants adapted to dry soils, consider altering the recipe above to 1 part compost, 1.5 parts coir and 1.5 parts sand. This formulation better mimics well-drained soil and reduces the likelihood of root rot.

Biochar

Biochar is another alternative to peat in potting mixes. Biochar is a charcoal-like substance made from heating organic materials at high temperatures in a kiln. It is used in potting soils to provide aeration, retain water, and support beneficial soil microbes. Biochar also traps atmospheric carbon dioxide in soil, reducing emissions.

Like coir, biochar can’t be used alone. It is typically mixed with nutrient-rich compost and sand to create a potting soil.

Organic compost

Peat-free organic compost is another alternative to peat in potting mixes. Organic compost is made of plant matter, vegetable waste, wood fiber, bark chips, and other organic matter. It is rich in beneficial soil microbes.

Commercial organic compost is typically formulated to provide sufficient nutrients for potted plants. Homemade organic compost has more variation in nutrient levels, and may need to be supplemented if it is too low in nutrients for growing potted plants.

Organic compost cannot be used on its own as potting mix. It should be mixed with coir or biochar for aeration and water retention, as well as sand or perlite to improve drainage.

Peat seedling trays at a garden center. — Avoid peat containers for growing. More sustainable alternatives are available.

Alternatives to Peat Containers

Peat isn’t only used in potting soils. Many biodegradable pots, trays, and planting containers are made from pressed peat. Peat containers are often marketed as an alternative to plastic containers, but they are just as unsustainable. Fortunately, biodegradable peat-free pots are available with lower environmental impacts.

Coir pots

Coir pots are very similar to pressed peat pots. They are sturdy and retain moisture, while remaining intact for several months.

That durability comes at a cost. While coir pots are biodegradable, the process is slow and gardeners are often advised to cut holes in coir pots before planting. This increases the effort and time spent planting, and raises the risk of transplant shock for seedlings.

Fiber pots

You can find a variety of fiber pots, made either of wood fiber or recycled paper fiber. Fiber tends to be used in seedling and hanging pots. Fiber pots are relatively durable, and some last for an entire growing season. However, fiber pots may take a long time to biodegrade after planting. It is sometimes necessary to cut the bottom off fiber pots before planting, so the plant roots can reach soil before the pot biodegrades.

Cow manure pots

Cow manure pots are made from composted cow manure and recycled paper fiber. I like using CowPots, which are made with zero-waste manufacturing powered by 100% renewable energy. They come in many shapes and sizes, and are porous to encourage root growth and air pruning. When planted in the ground, cow manure pots break down quickly, no cutting required. And, because manure is high in nitrogen, the plant roots receive a steady nutrient infusion as a cow manure pot biodegrades.

Cow manure pots are fantastic, but come with a couple considerations. These pots perform best when allowed to dry fully between waterings. This suits most plants, but may not be ideal for plants that grow in consistently wet soil, like some sedges and wetland wildflowers. Additionally, cow manure pots are intended for about twelve weeks of growing, after which they begin to break down. Timing is important when growing in cow manure pots, so you should start seedlings in trays, then plant the seedlings in larger pots after they grow two pairs of true leaves.

Reducing peat use is a process. Don’t beat yourself up if you find yourself using a potting mix that contains peat, or if you’ve already bought peat pots. We’ve all been there. As you learn, use your knowledge to guide future choices, and be bold in trying alternatives to peat! You might be surprised at how good the results can be.

Reducing Peat Use When Growing Potted Plants