|Rites of passage|
One of the hooks that got me into Permaculture was its conscious and demonstrable use of nitrogen fixing plants. This appealed to the obsession I had with these plants and broadened my understanding of the opportunities and techniques for their use. Sad person that I was, I had started out on my obsession by scouring fields and roadside verges for seeds of native legumes, bringing them home to strew in the garden and assess their likely perseverance. Not for me the green manures of the organic gardening clones, or the agricultural clovers of the ploughing brigade. I was looking for the ecological matches that seemed to serve nature so well.
Lesson number one was that native nitrogen fixing plants had a transient existence in a garden environment. Guess I should have realised that, as legumes do best in poor soil and that definitely was not what my garden was offering. Lesson number two was that the ornamental (or exotic) legumes that I grew had greater longevity. Two cheers for the Russell lupin, but I wish it wasn't such slug food, and would the Americans kindly take back all their lupin aphids?!
What I also saw in Permaculture was the use of the woody nitrogen fixing species. It was about that time that I learnt about Frankia, that other symbiont bacterium that fixes nitrogen, but which is so much more promiscuous than rhizobium, the monogamous symbiont of the legumes. Frankia doesn't do non-woody. That is, so far, since the eight or so plant families that have been found to nodulate with it are unlikely to be the only one on the list (quick research note: still the most infallible method to test for the presence of Frankia symbionts is to pull up non-leguminous woodies at random and look for nodulation).
The woodies have perseverance par excellence (a sort of perma-culture!). And these nitrogen fixing woodies lend themselves to development of site infrastructures that have multiple function - not for nothing have alders traditionally been used for windbreaks around market gardens. Do you think all of their users knew that they also fix nitrogen? Do the landscape designers working on highway median plantings know why the Elaeagnus bushes they plant grow so well? Have they ever eaten the berries? What is it about bog myrtle that makes it thrive in ground that makes your feet rot? Is there something strange about laburnum, gorse and brooms being the few examples of the woody legumes that we can call our own?
I was struck by the use of cuttable mulches in Permaculture, but it was the nitrogen-fixing woodies such as the wattles and tagasaste (both legumes) and casuarina (Frankia) that were grown for cutting, rather than the probably softer growth of the perennial herbaceous legumes. When you look more closely, these woodies have that soft growth themselves with the wattles (Acacia spp.) and casuarina also benefiting from being evergreen.
While I ducked the horticultural improbability of growing casuarina on my Yorkshire hillside, I gave the wattles a go, soaking the seed in boiling water before sowing in modules under cover. I went for three contrasting species: the Silver Wattle (A. dealbata) the long leafed Sydney Golden Wattle (A. longifolia) and the Prickly Moses (A. verticellata). When small, all made beautiful pot plants that were admired amongst my gardening friends, and I loved the distinctive smell that came from all their roots. However, one by one they perished through the winters leaving only the runt of a silver wattle that I eventually had planted out in my greenhouse border.
The runt was then 15cm tall when planted in out the greenhouse. Six years later, it is 7m tall with just over half its height growing out of the greenhouse, and wrecking it in the process. While it has grown, I have feared for its life each winter, and I have finally gone off the idea of using the woodies for cuttable mulch. But, in what must be a rite of passage in my evolution as a Permaculturist, I noted some nascent flower buds on the wattle in January this year. Would they open and bloom, or would they abort and stay tightly shut? I am delighted to say that the buds have now opened to lovely lemon-yellow puffs of scented flowers that glow brightly against the evergreen filigree of the foliage. Can I hope that the same will happen for me this year?
Mark Fisher, 5 April 2002