I’ve been doing quite a lot of reading about permaculture lately. What is permaculture? The word is derived from permanent agri- (and horti-) culture. Bill Mollison, one of its founding fathers, defined it as “the conscious design and maintenance of agriculturally productive ecosystems, which have the diversity, stability and resilience of natural ecosystems.” Some have defined it as evolved organic farming. The way I understand it, it is a way of growing trees, shrubs, vines, vegetable crops, herbs, and flowers (to attract pollinators and other beneficial wildlife) in the same space in a permanent and sustainable manner — i.e., without using a lethal cocktail of agrochemicals and non-organic fertilizers. I find that its planting principles are akin to other forms of integrating trees and crops into the natural landscape. These go by many names — agroforestry, natural farming, forest garden, multistorey planting, multifunctional forest, food forest.
Up to now I’ve designed and created gardens that were primarily ornamental, with a few edible elements. Now what I’m after is a food-producing and at the same time aesthetically pleasing orchard. If you recall, I posted a list of fruit trees a while back. Included among those were some nitrogen fixers –- shrubs and trees whose roots harbour symbiotic microorganisms (bacteria and other soil microbiota) that change nitrogen in the air into plant-usable form. The idea is that nitrogen fixers will supply sufficient nutrition to surrounding plants so that they will not need supplemental fertilizers. Fine in theory. But how to implement it? Where do you position the nitrogen fixers, and how many?
I am so glad I came across the Trios or NAP model, from Stefan Sobkowiak’s Miracle Farms. I can use it as a template for laying out my food forest. Trios stands for 1 nitrogen fixer, 2 fruit trees (NAP: N= nitrogen-fixer, A = apple, P = plum/pear). The idea is not to have the same cultivar or same type of tree close together, so as to minimize the spread of pests and diseases. I prefer not to have straight rows however. Stefan’s farm is situated in Quebec, where apples are the predominant fruit; instead, I am using olives, the existing trees in my garden.
Stefan uses the honey locust tree (Gleditsia triacanthos) as his nitrogen fixer. It grows fast and is tolerant of heat and cold, winds, and drought. Its small leaves cast a dappled shade, allowing crops that cannot take direct summer sun to flourish underneath. It’s quite thorny, but the variety G. triacanthos inermis apparently has few or none. Planted in between the large trees in the schema above are herbs, such as oregano, thyme, echinacea, chives and other members of the Allium (onion) family; and fruit shrubs (haskap, also known as honeyberry or Mayberry, is Lonicera caerulea, a Japanese/Siberian berry that resembles an elongated blueberry; raspberry; gooseberry, etc.).
I may use the honey locust together with lower growing nitrogen fixers with the additional benefit of edible fruits. Oleaster (autumn olive Elaeagnus umbellata, Russian olive Elaeagnus angustifolia) and sea buckthorn (Hippophae rhamnoides) are shrubs similarly hardy to heat, cold, wind, and drought as the honey locust. The sea buckthorn, also known as Sanddorn, is very popular in Germany where its Vitamin C-rich fruits are made into jams and cold-preventative teas. The Elaeagnus’s red berries and the sea buckthorn’s orange ones would be lovely hanging on the shrubs over autumn and winter. Birds are quite partial to them as well. And once they develop a taste for them, they might leave the cherries and other more desirable (to humans, that is) fruits alone.
I might also try the fast-growing nitrogen-fixing horseradish or drumstick tree, Moringa oleifera, whose protein- and antioxidant-rich leaves and pods are widely recognized for their health-giving benefits. I did not fancy this tropical vegetable as a child growing up in the Philippines, where I knew it as malunggay in Tagalog (marunggay in Ilocano), but I would be over the moon to have it growing in my garden now. Whether it will tolerate the cold winter in this mountain region is a question. Originally from sub-Himalayan regions of India and Nepal, it is said to tolerate light frosts, so worth a try.
Rooibos, the popular South African tea plant, is noted as a nitrogen fixer in this list; it would be fun to try too. For ground-hugging nitrogen fixers, I found medicago, coronilla, and diverse vetches (all leguminous plants) growing wild in the garden when we came. The only issue with relying on these is that they all dried up in the summer heat. Perhaps with drip irrigation installed, they might stay green all year round.
I shall be drawing up my own planting layout over the coming days, but I thought I’d share with you the process of designing my Mediterranean food forest as it develops. The planting combinations that I hope to use (in permaculture lingo, ‘guilds’) will consider the overall aesthetic effect as well. I might, if time permits, also check whether they will grow companionably together, or whether they could have allelopathic (negative) effects on each other. There is a lot of received wisdom out there on companion planting for vegetables and herbs, but not so much on trees and shrubs and vegetable crops all together.
If you’ve had any experience growing food crops with honey locust, autumn or Russian olive, sea buckthorn, rooibos, or any other nitrogen fixer, I’d love to hear from you.