Going peat-free

 I was encouraged to see a recent New York Times story about replacing peat-based potting mix with more sustainable materials. I just wish the writer, Margaret Roach, had gone farther and described her experience with the new materials.

Mer Bleue peat bog in Canada

    Peat has been the dominant ingredient in growing media for a long time because it’s great at absorbing water and nutrients but lets air and water flow through, and it’s slow to decompose. The problem is that peat is not a renewable material, at least on a human time scale. Peat bogs are giant carbon sinks, sequestering more carbon than all the trees in the world. Extracting peat from peat bogs releases carbon dioxide into the atmosphere, contributing to climate change.

    Peat forms very slowly when wetland plants decompose in oxygen-poor water. The peat we garden with took thousands of years to form. As we confront the climate emergency, we need materials for growing plants in containers that come without environmental degradation and a high carbon cost.

    When I learned about peat’s downside, I switched to making my own potting mix by combining sifted homemade compost with coir, or coconut fiber. This mix works just as well for my container plants as the peat-based potting mix I used to buy at the garden center. 

I combine coir and compost to make peat-free potting mix

     To make the volume of potting mix I need, I buy 5-kg compressed bricks of coir from a hydroponic growing outlet or Home Depot. You can also buy big bags of loose coir, but whatever kind you buy, it needs to have been washed to remove salts. To use it, just wet it by soaking in a barrel. Sounds like an easy solution, right? Unfortunately, coir comes with a carbon cost for shipping it here from tropical areas.

 

Container plants flourish in the peat-free mix

 
    From Ms. Roach’s article, I learned that US researchers are working on developing wood-based recipes for potting mix. Ideally, those could be made from local materials. She interviewed Brian Jackson, a professor at North Carolina State University and director of the Horticultural Substrates Laboratory. This is another area where Europe is way ahead of us. They’ve had wood-based growing media on the market for 30 years. Britain is moving toward banning peat in horticultural products.

An example of UK peat-free compost made from bark and wood

 
     Jackson’s team reports best results from a combination of peat and wood. Combining them creates a stable, spongy material that retains water especially well. It’s porous and provides lots of air space, creating an excellent environment for root growth. I’d rather drop the peat from the recipe completely. How about wood fiber combined with compost? That seems to be working in Europe.

     So far, wood fiber for growing plants seems to be available to large-scale growers in the US but not to home gardeners yet. While we wait, I recommend the coir-compost blend. But the best thing we can do as consumers is to ask garden centers to stock peat-free potting mix, whether it's based on coir or wood fiber. Why should Europeans get all the good stuff?

Force of habit

An ad for Sunsweet prunes I saw years ago has stuck in my mind ever since. It showed a snooty-looking young man saying, “I breakfast on prunes because Dad breakfasted on prunes.” That pretty well describes the rationale for a lot of our gardening practices. 

Trees usually don't need staking, but it's a tradition

    I recently told a garden club why I’ve switched to no-till methods for my vegetables and annuals. Organic no-till agriculture is a well-established technique that avoids disrupting the rhizosphere, the top few inches of soil where most of the biological activity happens.

The rhizosphere

 

It enables farmers to benefit from the work of soil organisms that, if undisturbed, convert organic material into nutrients that crop plants can use. In home gardens, not tilling saves a lot of work; you can skip the sore back that used to result from turning the soil in spring with a spade or Rototiller. It also allows sequestered carbon to stay in the soil, helping to combat climate change (For a practical guide to the many benefits of no-till methods, see Lee Reich’s Weedless Gardening).

    On this occasion, one of the garden club members “attending” my talk on Zoom firmly rejected the idea of not tilling. “We don’t do that,” she said. She was certain that rain and snow pack down soil, and it needs fluffing up before planting can be undertaken.

 

Managing to thrive in a no-till bed

 
    Her reaction mostly shows that I’d failed to explain no-till gardening convincingly in this attenuated online format. But I thought I also detected a whiff of “Dad breakfasted on prunes.” A lot of the things we do automatically in our gardens were passed down from our parents or gardening mentors. 

People think trees need winter jackets. They don't.

Other techniques became part of the ambient conventional wisdom when garden writers recommended them over decades without scientific confirmation. These practices are so familiar to us that we don’t even notice we’re doing them, let alone examine the reasons behind them.

    I have no trouble resisting the impulse to turn over the vegetable bed with my spade before planting. I’m all too happy to have a reason to forego that annual ritual. But what about pulling up weeds? That’s where I have to fight long-established reflexes.

 
    A true no-till gardener doesn’t uproot weeds, because doing so disrupts the networks that underground organisms have worked to create. And decomposing roots nourish soil and make channels for water, air and nutrients to flow through. What I should be doing is cutting the weeds off at ground level, leaving the roots in the soil. If they resprout, like dandelions, I should lever them out with minimal soil disturbance. It’s hard, though. It takes work to build new habits.

It's best to pry dandelions up without digging-photo Sunasce007

    That encounter with the garden club skeptic made me realize that I’m advocating evidence-based gardening. I believe that science should be our guide. Sometimes science confirms the wisdom of traditional methods, showing that they were better for the environment than newer approaches premised on overuse of chemical fertilizer, herbicides, and pesticides. In the case of tilling the garden, though, Dad had it wrong.

 

My insectary bed is a no-till area

 

Climate action in the garden

It’s been a discouraging month of environmental news. The UN climate summit confirmed that there’s not a lot of time left for international action to prevent catastrophic climate change, but national governments, notably ours, are not making adequate commitments. 

Unlike polar bears, we humans do have the power to combat climate change-photo Gerard van der Leun

A group of ornithological organizations published a study estimating that we’ve lost 3 billion birds--29 percent of the bird population of the US and Canada--since 1970. Leading causes cited included habitat loss and widespread use of pesticides. The Audubon Society reported that by 2080, 389 out of 604 North American bird species will find most of their current ranges unlivable if the climate remains on track to rise by 3 degrees Celsius.

No more loons on US lakes unless we clean up our act-photo Bert de Tilly

    While our national leaders are dragging their feet, what can we gardeners do to address climate change? Collectively our gardening choices can make a real difference. We can do our part by holding carbon in soil and plants, planting strategically to reduce our homes’ energy needs, and choosing materials with less embedded carbon cost.

    You’ve undoubtedly heard that saving trees—for example not burning down the Amazon rainforest or clearcutting Forest Service land in the Northwest—can help combat climate change. The same principle operates in our backyards. Trees hold carbon and keep it out of the atmosphere for as long as they live. Perennial plants also contribute.

Big trees sequester lots of carbon-photo ukgardenphotos

    But you don’t have to hem in your yard with big trees. We can also help by following Earth-friendly gardening practices. Soil sequesters carbon, and the more organic material you add to it, the more carbon it will hold. That means keeping fallen leaves on your property makes even more sense. 

It's not waste, it's precious organic material

    If you’re planting a sizable tree, you can help even more by positioning it to reduce your energy use for heating and air conditioning. Deciduous trees shading the house in summer can provide substantial cooling, and in winter when leaves are down, they allow warming sunshine through. Evergreens that block winter winds can reduce energy needs too.

Trees shading the house save energy-photo American Society of Landscape Architects

    When we’re shopping for materials to use in the garden, we have a chance to avoid high embedded carbon costs. For example, did you know that those little white pellets of lightweight perlite that you see in bagged potting mix come to us from the Greek island of Milos, where volcanic glass is mined and heated to 1600 degrees Fahrenheit to puff like Rice Krispies? Meanwhile, stripping peat bogs for the peat moss in that commercial potting mix releases carbon into the atmosphere and eliminates the carbon sink they provided. 

Mer Bleue peat bog, Ontario

    Instead of buying bags of this environmentally costly stuff, you can make your own potting medium at home. Or you can choose Organic Mechanics potting mix, which is made from compost and coconut fiber, or coir.

Making peat-free potting mix at home

    If you’d like scientifically informed straight talk on how to make shrewd gardening choices that will help combat global warming, check out The Climate Conscious Gardener, published by Brooklyn Botanic Garden.

Sign for the April 2017 Climate March in Washington, DC

Doing something about the weather

I thought snowdrops blooming this week were the earliest I’d recorded, but looking back I see I spotted some on January 31 in 2012, another winter with very little snow.

Snowdrops are blooming early

In recent years, I’ve noticed spring growth starting earlier. Scientific data confirms this trend is affecting wild plant populations. Our climate is changing, and gardeners are on the front lines.
 

Witch hazel buds are already opening

     I’m finding the lack of snow cover ominous this year. Is this the new normal? Last year demonstrated the kind of damage that our plants suffer when they experience blasts of cold weather without the insulating protection of snow.

    The New York Times recently reported that farmers in Kansas are talking about changes in the weather, although many still don’t blame human actions for causing global warming. One farmer they spotlighted also spoke about sequestering carbon in the soil. On a much smaller scale, that’s something we can do too in our backyards. 

     Brooklyn Botanic Garden offers The Climate Conscious Gardener, a handbook of useful approaches for minimizing the carbon footprint of your garden and sequestering carbon in your soil and plants. 

    With Congress and the Trump administration rolling back restrictions on methane leaking from oil and natural gas rigs and wells, it’s even more important for us to seize the opportunity to be good climate stewards. 

     Methane is a greenhouse gas 21 times more potent than carbon dioxide. Federal regulations restricting its release were intended to fight climate change. Now with climate change deniers having their way, oil drillers and frackers hope to be spared the trouble and expense of preventing methane release. The planet and everyone on it will pay the price.
 

Gas flare from North Sea oil drilling--photo by Varodrig

    Some of the steps the BBG handbook recommends:

Planting trees. We’ve all heard about this as a way to keep carbon out of the atmosphere. Long-lived trees are best.
 

The dense wood of this tall white pine sequesters lots of carbon

Siting trees and shrubs to provide windbreaks and shade. This will reduce your house’s energy needs for heating and cooling—and save you money. 

Minimizing digging or, even better, switching to no-till gardening. When we dig, we introduce oxygen that speeds up decomposition of organic material, releasing carbon into the air.

Recycling fallen leaves and garden waste as compost. When you keep organic material at home as compost, you’re holding onto carbon. 

Applying organic mulches. Mulches made from materials you can get close to home are especially carbon-thrifty. I like to mulch with shredded or whole leaves and arborist wood chips.
 

Wood chip mulch holds carbon

Shrinking your lawn. Every other landscape feature requires less energy, petrochemicals, and water for maintenance.

Skipping peat-based potting mix. Peat bogs are a major carbon sink, sequestering more carbon worldwide than trees. When peat is extracted, carbon is released, and the carbon sink it provided is lost. It’s easy to make homemade potting mix from compost and coir (coconut fiber).

By following some of these recommendations, we can be part of the solution locally, even when the federal government is going in the wrong direction globally.

Neck deep in the Big Muddy