Last week, the IPCC released its latest report on climate change. In the most basic terms, it says we need to get to net negative carbon emissions ASAP and prepare for things to keep getting worse over the next few decades. As I skimmed the report, a burning desire to go out to the garden sidetracked me. I planted some heirloom Calima French filet bush beans that will be producing in under two months.
Now those seeds have germinated and begun developing roots. Even at this early stage, the roots are already collaborating with complex systems of soil life to collect nutrients in exchange for carbon exudates that my beans will make through photosynthesis, over their life span.
Essentially, plants are natural carbon scrubbers. They take carbon dioxide from the air using solar energy and convert it to plant-usable carbon. Then, they make leaf mass, stems, roots with carbon and share extra carbon in liquid form with soil life.
Underground, the carbon enters the soil food web where it stays in circulation through various iterations and lifecycles until it eventually breaks down into humus. Humus is a magical stable substance that makes soil fertile, moisture retentive, and plant supportive.
When my Calima beans stop producing, I won’t yank them out or till them in which would release carbon. Instead, I’ll cut their tops down at ground level and leave them on my beds. The carbon they fixed in their leaves will decompose and enter the same rhizosphere the carbon exudates went. So will the carbon stored in the undug roots.
Nitrogen and Carbon
Mature bean plant matter has a ratio of carbon to nitrogen between 20-25 parts carbon to one part nitrogen. Soil life normally operates at around 8 parts carbon to 1 part nitrogen. So, to decompose bean residue into soil stable carbon and nutrients, soil life will borrow an extra 1.5 to 2 parts nitrogen from the surrounding soil. This process, often referred to as nitrogen binding, is only a short-term loan that will be repaid in spades not long after the decomposition is complete.
Storing carbon is such a high priority to the systems of soil life that they will deprive neighboring plants of nitrogen in the short-term to get the job done quickly. That can often result in short-term plant stunting with later bursts of fantastic growth.
Of course, weeds growing in that soil when that nitrogen frees up often have epic growth too. So, you want to make sure you keep controlling weedlings until your plants grow in.
Side note: This nitrogen binding often happens when we apply fresh compost to our vegetable beds. Existing weeds are temporarily stunted while soil life borrow nitrogen to finish processing that unaged compost into soil usable carbon. At first, it seems like the weeds are controlled. Then all of a sudden, the garden bed is taken over by weeds once the nutrients are freed up. You can avoid this problem by aging your compost for about a year before use. Alternatively, plan to do extra weed maintenance a couple months down the road when using fresh compost.
Many factors control how quickly that carbon storage and nitrogen return happen, e.g., condition of the soil, temperatures, and moisture levels, etc.. In my vegetable garden, it takes 2-4 weeks. That makes it the perfect time frame to germinate slower growing vegetables and herbs. For fast-germinating plants, I water with compost tea to get them through until the nitrogen is free again.
The one downside to this kind of no till gardening is that sometimes larger critters like worms, helping with the decomposition, eat my seeds. I plant extra to ensure enough plants germinate. Then, I thin extra plants with scissors as needed. Every so often, I have to re-sow in a spot or two.
Perennial plants also send carbon exudates deep into soil. However, since their roots extend deeper and aren’t routinely disturbed, the carbon they fix can be more securely stored in soil. Herbaceous or deciduous perennials, that lose their leaves annually also deposit carbon on top of soil. However, unlike the chop and drop I do with plant tops in the vegetable garden, their natural leaf drop happens as plants approach winter dormancy. Then, they naturally use less nitrogen.
Evergreens also drop their leaves to increase the carbon in the soil, just not all at once. As such, the nitrogen demand they put on the soil is far more regulated than with other plants. That makes them a terrific source of stability for soil life.
Carbon Capture Complexities
At a time when the IPCC is raising the alarm level to code red about how imperiled our civilization is if we don’t reduce atmospheric carbon and use more solar power, plants as carbon scrubbers seem like a miracle solution to all of our problems. Unfortunately, it’s not that simple.
Humans have occupied, developed, and degraded so much of the land that once would have supported plant growth. We’ve filled it with roads, houses, office buildings, shopping malls, massive warehouses, hospitals, and more. Or, we’ve made the soil conditions so terrible that even invasive weeds won’t grow well. Also, let’s face it, climate instability makes it harder for plants to grow.
On top of that, much of the prime land for growing plants is used by agriculture. Between tilling which oxidizes carbon and makes it airborne, the use of carbon-intensive synthetic fertilizer and herbicides, and of fossil fuel dependent machinery — agriculture is a top contributor to more atmospheric carbon.
There are many farmers trying to change that model. Regenerative agriculture, carbon farming, silvopasture, and lots of other ways of sinking carbon while producing food and other human resources are gaining popularity. This week I read about wine makers and olive growers in Spain who have started growing select species of ecologically supportive plants in what was once the herbicide sprayed, heavily mowed, and even tilled area between vines and trees.
At the scale plant-based carbon capture is happening today, it will never be enough to prevent the worst consequences of climate change. We also have to focus on using a lot less carbon in our daily lives and finding innovative ways to capture carbon. Yet, every bit helps.
Also, the more we do these things, the more we learn. Then, the better prepared we are to share information when the rest of the world is ready for a carbon farming revolution (to replace the outdated green revolution). Supporting farmers focused on carbon sequestration is a great way to help encourage more of that kind of good work.
An Army of Carbon Gardeners!
Farmers aren’t the only people who grow plants though. There’s literally an army of gardeners out there able to react more quickly than big agribusinesses and speed up carbon capture at home. And, the pandemic has even added 20 million new gardeners to our ranks in just the US alone.
Together, we can actively fight against the worst consequences of climate change and have resilient, beautiful gardens in the process! Because we aren’t for profit producers of commodity crops with impossibly tight margins, home gardeners have more freedom to choose how we garden. We don’t have to garden like farmers. We can garden more like nature does — by prioritizing the continuous increase of soil stable carbon over the long run.
Also, increasing carbon in soil isn’t just good for the climate, it’s good for garden health. Carbon rich soil is like a bunker for soil life and a safe haven for plant roots. It retains more water than low carbon soil. That makes it a sponge in heavy rains and a water reservoir during dry periods. Plants grown in soil replete with stable carbon, particularly in the form of humus, develop stronger stems and are more resilient against above ground challenges.
We won’t solve all of our problems by putting as much carbon back in soil as possible. But we can certainly make a good start using our gardens. We can also enjoy healthier gardens better able to withstand the changes to come.
Carbon gardening – as in gardening with a specific focus of reducing carbon in the air and putting it back into the soil like the future of our planet depends on it — is not hard to do. In fact, it’s easier and less costly than conventional gardening over the life of a garden. But it does require letting go of some outdated ideas of what it means to garden.
Reduce, Reuse, Recycle
The biggie is that for meaningful carbon gardening you need to buy as few single use products as possible and instead focus on gardening for a stable climate future. Everything you buy to use in your garden has a carbon cost associated with it. So, the more you buy, the bigger your carbon footprint related to gardening.
When you first start a new garden, sometimes the soil is so bad that you need to buy inputs like mulches and compost or manure (not made by your livestock). If you can source those materials nearby such as from tree services and farmers, or use waste products from local industries that can minimize carbon costs.
Of course, I also believe that gardens need to be beautiful and durable for us to enjoy them and want to spend our time building soil and caring for plants. So, making one-time purchases of the design elements you need to make your garden a sanctuary for you to enjoy are also worthwhile carbon costs.
You can recoup those carbon costs though, by using your garden to reduce your carbon footprint by growing food, flowers, herbal medicines, craft supplies and more at home. You can even use plants like fruit trees and grape vines or hedges to help cool your home in summer or protect from wind in winter.
Long-Term Carbon Reductions
Beyond those initial start-up carbon costs, once you get gardening, there are lots of ways to reduce your carbon costs while increasing carbon stored in your soil long-term. Here are some of my favorite ways to practice carbon gardening.
Tip 1: Grow Weeds
I know it sounds crazy for the author of Weed-Free Gardening to say “grow weeds”. But frankly, growing weeds is a smart way to improve soil health, solve nutrient imbalances, and increase carbon capture in your soil so that you can ultimately have a healthy, weed-free garden. You just need to grow weeds responsibly and for targeted purposes.
Weeds are free plants that already exist in your landscape for free — with no carbon costs. So, why not use them as cover crops? Chop and drop them several times to start preparing your soil before you expand your garden. Or how about growing a weed patch away from your garden to specifically cut and use for your compost pile?
Personally, I’ve become a big fan of wild blackberries. They have lovely flowers that pollinators love. Plus, they produce edible fruit that’s perfect to use for homemade blackberry sparkling wine. They also make terrific hedges and thickets for wildlife. When they get out of hand, I cut them up into pieces and dry them to use for biochar feed stock.
If you’ve read my book Grow Your Own Spices then you already know I love Staghorn Sumac as a spice. But I also love mowing the saplings down as a natural mulch around the plants I let grow.
Choose, grow, and use weeds that make sense as carbon-reducing resources for your needs. Then compost the rest.
Tip 2: Propagate Plants
Commercial plant production comes with a lot of carbon costs. Those plastic pots, synthetic fertilizer, transportation costs, etc. all add up. Supporting local, organic plant sellers and returning plastic pots when you go to make new purchases can help. But you can also buy just one or two of each of the different kinds of plants you want to grow in your garden. Then, you can use those plants to propagate the rest that you need.
Taking stem cuttings or collecting seeds are easy places to get started with plant propagation. Bulbs and corms usually reproduce themselves and can be carefully dug up and divided periodically. Some plants produce multiple crowns that can be divided. Others can be reproduced by root cuttings.
It takes a longer to propagate your own plants. But that gives you time to prepare your soil, salvage natural materials for decorations and beds, and generally hone your self-sufficiency skills in the garden before you have more plants than you are ready to care for growing all at once. Plus, it gives you time to age your compost.
Tip 3: Make Compost
Compost is one of the best ways to get stable carbon back into your soil. By collecting kitchen scraps, cardboard, paper, weeds, manure, leaves neighbors don’t want, and pretty much any organic matter you can get you your hands on, you can build large piles that heat up, kill pathogens, and become compost in just a few weeks.
The bacteria that decompose hot compost aren’t the same ones that are beneficial to your garden soil. After you make that compost, you ideally want to wait a year to use it. That way it can be more finely decomposed and colonized by the beneficial bacteria that operate at normal soil temperatures. Aging also increases the humic content in compost.
Less-aged compost, by contrast, may require nitrogen from the soil to process and can produce more weeds that you’ll be tempted to pull. Of course, pulling out weeds — roots and all — is pretty much the same as tilling.
Tip 4: Don’t Till
Tilling is the perfect way to release carbon from soil back into the atmosphere. So, in a carbon garden, you need to avoid it as much as you can. It’s hard at first to resist the urge to turn up the soil. The smell of fresh turned soil seems wholesome and good. Except that it’s not. That smell is carbon wafting into the air where we don’t want it!
Tilling, and disturbances like ripping out large weeds, or even thinning plants too late can add up to net carbon losses instead of the gains you are going for. There are times you need to harvest roots. But in that case, you may want to designate beds that will be used for root harvests so you can add extra compost to compensate in those beds.
Tip 5: Populate with Perennials
Even if you are growing an annual vegetable garden, integrate as many perennials as you can. Those stable perennial root systems are safe havens for soil life. So, they offer corridors of continuity even in times of rapid soil change such as if you do have to uproot some underground tubers or pull a particularly aggressive colonizing weed.
Tip 6: Plant for the Future!
Finally, once you start carbon gardening, keep your soil as well-stocked with plants as you can. If you pull out a root, put in a seed or a new transplant. If you are going to mow down a crop and leave it to decompose on top of soil, plant your next crop before it is fully decomposed.
As your soil depth and fertility increase from carbon gardening, you’ll also be able to more densely stock your plants in that deeper, humus rich soil. So, if after a year or two of carbon gardening you notice your beds are getting weedy, that’s your signal to start using closer spacing and increase your cultivated plant population.
And, seriously… what gardener doesn’t want an a reason to grow more plants?!
Carbon Gardening Goes Viral!
These tips are a good starting point for carbon gardening. Ultimately though, it takes more than you and me to make a big difference in our climate future. It will take all of us to solve these problems. So, I also hope that as your garden grows, you’ll share your knowledge with others and encourage them to create beautiful, carbon rich gardens too. (You can also share this post with anyone you think might want to carbon garden!).
Honestly, I don’t know what the future climate holds because the outcomes depend on so much outside my control. But I do know that having a beautiful garden, with carbon rich soil that makes it more resilient going forward, is going to sustain me and keep me hopeful for the future.
May your garden be truly green in every way possible!
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