Winter… finally time to sink into gardening theory and read all the books you didn’t have time for in the spring. (Also, for me, back to fiber arts, but that’s off-topic.)
What’s really fun about reading gardening books is finding contradictions. Permaculture hasn’t been around long enough for its published material to agree on everything (if that is truly even possible in any field…) The great and amazing Edible Forest Gardens advocates planting your trees on a slight rise of soil with a small bulwark around, so while rain falling within that bulwark can be caught for the tree’s future use, further rain will not collect and drown it. It is geared towards the Central/Eastern areas, Ohio and eastwards – in a more clay-y soil, higher rainfall area. Rainwater Harvesting for Drylands advocates planting trees in depressions to capture all the water possible. It is written for the sandy soils and lack of rainfall of the American southwest. So where does North Dakota fit in? In the central and eastern part of the state, we have clay soil that takes ages to drain; and in the central and western part of the state, we USUALLY have an arid-climate type of rainfall. How do you resolve these contradictions?
|USUALLY arid climate, I said, USUALLY|
Moving in the second direction here, the North Dakota Extension Service has lately been advocating the creation of rain gardens . The concept is a basic permaculture principle, namely, “why do extra work yourself when you can use existing natural functions to do the same thing”: We should store water directly in the earth that will be using it. Why pay extra money for plastic rain barrels to store your roof water until the garden beds need it (and have to guard them from mosquitoes), or, even worse, why let excess water drain into the sewage system and pay for new water later? Soil has a large proportion of open “pore space” that is filled with air; a great deal of water can filtrate in and occupy these spaces before soil will start to seem soaking wet and hurt existing vegetation.
The key to the rain garden concept is to increase the soil’s ability to hold moisture, by compensating for its speed of intake. During a good rainstorm, the rain falls faster than the soil can absorb it, so excess water drains from the surface. If you design an earthwork with a valley to collect the water, the water will stick around long enough for the soil’s rate of absorption to catch up to the volume of water and capture it too. This solution doesn’t scale indefinitely – you only want your water-collecting earthwork to hold a volume that can be fully soaked in by a day or so, with the aid of wood mulch to help keep it covered. Standing water, whether in plastic rain barrels or in puddles, = mosquitoes.
The Extension Service’s brochure is a good first step, a good concept demonstration, but it doesn’t take things as far as it can. It addresses the Mosquito Objection, but not “I don’t want to store extra water in my soil, I already have basement leakage problems in storms.” Properly designed, a rain garden can channel water quickly away from the foundations of your house towards specific areas in your landscape. Combined with a thoughtful planting layout and perhaps supplemental watering capability, you don’t have to stick to the ornamental “Mediterranean” plants that can tolerate wide variations in moisture levels – you can use a rain garden as a vital component in raising a “forest” of your favorite fruits and vegetables with a minimum of external inputs.
Bill and Becky Wilson of Midwest Permaculture have gone in this last direction. Check out their photo-account of a rain garden design that nurtures fruit trees and edible perennial and annual plantings, but is robust enough to handle their entire property flooding.
If this interests you:
- Read the NDCRS brochure for a quick summary and how-to, and check out its resources section – especially the link to the City of Mapleton, which has done some nice design plans for ornamental gardens.
- When you’re ready to progress from ornamental gardening to food-producing permaculture, read Gaia’s Garden to get inspired about what simple earthworks and swales can do to transform a dry-baked property into a self-perpetuating green oasis.
- Then, when you’re ready to actually Do It!, read Rainwater Harvesting for Drylands for the actual methods of transforming your property into a water-harvesting machine.