Peat Moss? Who needs it?

“Do you know what sphagnum peat moss is? Do you know what it’s used for?”

Several years ago, I decided to ask some members of the audience at one of my lectures these questions. Fifteen out of 20 people did not know what peat moss actually was, including the manager of a garden center. (He thought it was the same as compost.) Perhaps more surprisingly, seven out of the 20 people did not know what peat moss is supposed to be used for (although they all bought it). One person said her husband spread it on their lawn. Some of the people suggested that peat moss was a mulch to put on top of the soil.

Peat moss is the partially decomposed remains of formerly living sphagnum moss from bogs.  Because it’s nearly impossible to rewet once it’s dried, it repels water, and therefore, it is terrible surface mulch.  As a soil amendment, which is what the baled product at the box stores and garden centers is mostly sold for, peat moss is also a poor choice.  It breaks down too fast, compressing and squeezing air out of the soil, creating an unhealthy condition for plant roots. The same situation occurs in flowerpots. Peat moss is most commonly used as a container-growing medium in the nursery industry. If you must use peat moss for your large containers since nothing else is available, add plenty of perlite for drainage and to keep a bit of oxygen in the mix.

There are more problems. Peat moss is incredibly acidic. Its low pH is between 4.7 and 5.2. Neutral pH is 7 on a logarithmic scale (from 0 to 14): pH 6 is ten times more acidic than pH 7. Most herbaceous perennials want a slightly acidic soil in order to take up nutrients – around 6.5.

Another issue with peat moss is that it’s environmentally bankrupt.

Peat moss is mined, which involves scraping off the top layer of living sphagnum moss. The sphagnum peat bog above the mined product is a habitat for plants like sundews, butterwort and bog rosemary not to mention the living moss itself, as well as rare and threatened animals like dragonflies, frogs and many birds. Despite manufacturers’ claims that the bogs are easy to restore, the delicate community that inhabits the bog cannot be quickly re-established.  Yes, peat moss is a renewable resource, but it can take hundreds to thousands of years to form.

Like all precious wetlands, peat bogs purify fresh air and even mitigate flood damage.

And there are archeological reasons to preserve peat bogs.  In the acidic moss below the living layer, wooden artifacts of people who lived long ago survive, even the remains of the people themselves.  CO2 is also preserved – trapped in the moss, but released into the air when mined. In fact, peat bogs store about 10% of all fixed carbon. In the U.S., peat moss is almost exclusively used by the horticulture industry. 40,000 acres of sphagnum are currently being harvested in Canada, with 90% of the product destined for gardens in the U.S. In the U.K., where peat moss is burned as fuel, as well, nearly 94% of the lowland bogs have been altered or completely destroyed due to harvesting.  And most of our peat is shipped hundreds of miles, often when it’s wet and heavy, which adds further to the fuel required for shipping.

Many conservationists, gardeners, and wetlands scientists in these countries have recommended a boycott of peat. The Royal Horticultural Society hoped for a 90% reduction by 2010.  Areas in Ireland have already banned the harvesting of peat moss altogether.

Producers in both Canada and the United States maintain that they never cut sphagnum faster than it grows, and leave behind enough peat to ensure regeneration. The Canadian Sphagnum Peat Moss Association claims that peat-moss operations keep the bogs from being drained for development, that five to ten years after harvesting, the bog will be a “functioning wetland” again, and that after 25 years, 90 percent of the original flora will grow back.  I have my doubts. Some wetlands scientists point out that a managed bog lacks the biodiversity of the original bog.

In a development at the center of the gardening world, Monrovia Growers has just introduced a new line of bagged “soil” which contains peat moss.  That’s according to their press release about the products; the word “peat” never appears on their website. Scotts Miracle-Gro is selling a (“organic”) potting mix that contains their fertilizer. I have done tests with this product, and in some cases, it killed the plants I tried to grow in it. I grew plants in the bagged potting medium and side by side with just peat moss and perlite, which did not kill the same plants. Indoor plants do not need or want fertilizer in the winter – they can’t use it when they are semi-dormant. I believe the fertilizer burned the roots and led to their demise.

Though gardeners seem to have been programmed to buy peat and are as loyal to the product as some car-buyers used to be about their beloved Pontiacs, there’s simply no need to use it. In addition to homemade compost, I use coir, a byproduct of the coconut processing industry.  (Here’s one source.) This formerly discarded material can be shipped completely dehydrated – very lightweight – which reduces its energy requirements for transporting. There are complaints about salt in these products. Some companies say the material is washed. Although this is a potential issue, I have not come across problems with seeds/plants grown in the material.

Chopped leaves make much better and more attractive mulch, and leaf mold and compost are superior as a soil amendments. If only more Americans could be encouraged to compost.  If only corporations started their own composting facilities, and if only more municipalities got serious about composting.