By Kathryn Pankowski
Carbonate your garden? It’s not quite like carbonating a fizzy drink, though it may make your garden more effervescent. What I’m talking about is using your garden as a tool to fight climate change by pulling carbon out of the air and storing it in the soil.
And in case you’re about to skip off to some rival column, thinking “Oh, no, more doom and gloom, more things I’m supposed to give up”, know that using climate-friendly garden techniques will give you a better garden and an excuse to get more plants. (And every gardener wants more plants, right?) You probably do a lot of these things already.
So here’s the issue: scientists estimate that about 1/3 of the carbon dioxide increase in the atmosphere got there because, through poor forestry and farming practices, we released carbon formerly held in soils and plants (like the giant trees that once covered much of Vancouver Island). Getting that carbon out of the atmosphere and back into plants and soils can help solve the problem.
Plants take carbon dioxide from the atmosphere and put back oxygen, without the carbon. Most of the carbon stays in the plant, but some of it is converted into compounds and exuded through the plant’s roots. If there’s a good mycorrhizal (fungal) network underground, as there is in undisturbed soils, then the fungi will move the carbon into the soil and sequester it away.
So what can you, as a gardener, do to make your garden the biggest carbon store possible?
Aim for maximum biomass.
The more greenery, the more carbon tied up in plants.
· Preserve mature trees. Old trees are great carbon stores and the anchors for fungal networks in the soil. If you’ve got one, keep it healthy.
· Plant more trees and shrubs. Even if you have limited space, there are columnar trees that fit into townhouse courtyards and dwarf fruit trees that can grow on balconies.
· Replace a fence with a hedge or mixed-species hedgerow.
· Grow up (the plants, not you): trellis plants against walls and fences, grow roses up trees and clematis through shrubs, grow runner beans up poles and squash on arches, vines along balcony rails.
· Plant in layers. Our natural landscape has four layers: trees, shrubs, a field layer of non-woody plants, and a ground cover layer of creeping plants and mosses. See how many layers you can get into one bed or planter. Reduce your lawn – a one-layer area - to what you really use.
· Cover the ground with plants. Use plants instead of bark mulch between shrubs and a cover crops to avoid bare ground in the veg patch.
· Restore growing area. Depave - I need to evict a couple of concrete slabs that once supported an oil tank and TV antenna. Do you need a concrete parking slab or will a permeable paving or two ‘tire tracks’ do the trick? Can you add a growing box above your garbage cans or the doghouse? Or a green roof for the shed?
Love your mycorrhizae.
It’s these fungal networks that store carbon in the soil so it’s not released again when a plant dies. (This bit is only for people who garden in the ground; there’s not much you can do to build a mycorrhizal network among balcony pots.)
Don’t till the soil. Dig as little as possible. Build new beds by sheet mulching, mounding up organic matter on top of existing soil.
Feed the soil, not individual plants. Add home-made compost, composted manures, and leaf mulch to the surface of your beds, let the soil microorganisms do their thing, and you’ll keep both plants and fungus happy.
Plant more tough perennials and fewer plants that are pulled out or lifted each fall. (There are perennial forms of many common veg, such as kale and broccoli.)
Catch weeds when young (easier said than done) so they can be removed with little ground disturbance. Tackle perennial weeds, such as blackberry, by cutting them off at ground level regularly rather than trying to dig them out.
Don’t use fungicides. Ever.
Want to know more?
· For a more detailed description of how plants and fungi store carbon, see Gardening, Healthy Soil, and Carbon Sequestration on the Ecological Landscape Alliance website at https://www.ecolandscaping.org/01/climate-change/gardening-healthy-soil-carbon-sequestration/.
Charles Dowding offers lots of good advice on applying these principles to food gardening at https://www.charlesdowding.co.uk/
The Compost Education Centre has excellent instructions on how to build a no-dig bed. See Fact Sheet 7 at www.compost.bc.ca.
Kathryn Pankowski is the James Bay Neighbourhood Association Neighbourhood Gardening Advocate: she can be reached at firstname.lastname@example.org. The JBNA would like to acknowledge the financial support of the City of Victoria for this initiative.