I tend to be suspicious of the native plant movement: it smacks of horticultural xenophobia, and as much as I hate scotch broom and kudzu, I’m not convinced that native plantings are actually more appropriate to an urban habitat than other plantings. I’ve had a hard time getting an explanation of why it matters, just exactly the sort of thing that makes me nuts. Folks come round our garden all the time, full of advice and ideas and vision and I have a hard time filtering the wisdom from the BS. I know that dismissing native plants is blasphemy, especially for a commited organic gardener and permaculture dabbler, but no one was ever really able to tell me why.
This Christmas, however, I actually got an explanation that made some sense to me. My mother’s friend Billie has been active in a native habitat restoration project in the San Francisco Bay Area (I’m hoping my mother will read this and email me some specific names …) where recent restoration of a variety of native berry bushes, not popular in modern, manicured gardens, has led to the return of a warbler not seen nesting in San Francisco in fifty years. That makes sense to me, because birds are important and creating bird habitats is important, else you’ll be overrun with starlings, chasing any other birds off.
Fundamentally, you have a choice. Spray with pesticides and create a hostile and toxic environment; kill off all insects, predator and prey alike. The prey, the aphids and mites, long ago adapted to short life cycles and to flourish against all odds, will come back. Their predators, the ladybugs and lacewings and countless others that never get talked about, never had a chance. Their life cycles are much longer, and if you kill off a generation, it will take them a long time to return. Meanwhile, you’ll have to spray again if you want to keep the aphids in check, and spraying will keep the ladybugs from ever returning.
Or? You let nature work. You rinse off the aphids and plant things that will attract beneficial insects, along with flowers that will lure the aphids away from your tomatoes. You go out of your way to make room for birds, and you teach kids about why spiders are good for a garden. You won’t have a bug free garden, but last time I checked, you could make the whole neighborhood sick with chemicals and still not kill off every last mite and thrip. It isn’t perfect (nature is still nature) but it isn’t toxic.
One thing I know is that green roofs can make a big difference in bird habitats–more fragile urban birds need places to rest between trees, and mile upon mile of tar roofing does not provide much relief. Birds, in turn, do their part to keep the mosquitoes down (as do bats but we’ve been too spooked by the prospect of introducing rabies to put up our bat house) and spread seeds. We are hoping to introduce a kestrel to the garden this spring, perhaps she (he?)’ll keep our wee mouse population in check. Kestrels being raptors, you know I have a special affinity for them.
What I am trying to put together is some nice, succinct explanations of why greenroofs, native plants and organic gardening matter to the urban environment. And why the urban environment matters to folks who think they don’t care about it. That was one of the issues I wanted to start to tease out with this blog, that and why nutrition matters (in the meantime, see a great article in The Ecologist about the connection between sugar, vitamins and anti-social behavior (it is a British magazine, they talk alot about anti-social behavior in Britain))
Another little tidbit on the urban ecology front, file under “Nature Works Best Left to Her Own Devices”– the Brooklyn Botanic Garden is offering a lecture by Thomas Ogren on the impact that male-only landscaping has on pollen counts. In dioecious species, male trees don’t drop seeds all over the place, they don’t fruit or flower. A landscapers dream. Only problem is that what male trees do produce is pollen. Lots of it, and if there aren’t female trees around holding out their flowers, waiting expectantly for pollen to arrive, that pollen just floats. So between no female trees and no female trees, we’ve got twice as many pollen producers as we ought and no place for the pollen to go. BBG has no info on the lecture on their website but it is April 18 (a tuesday) from 4-5, and it is free.
PS, speaking of invasive species, I’m still waiting for someone to just harvest the ailanthus that grows wild in New York City. Enough trees are brought down every day in this city that at least some of them must have some value as rustic lumber, non?
