Class notes by Trisha C.
John Valenzuela visited our class this week, to talk with us about plants, trees and agroforestry. I have to admit, I’m a bit of a nerd when it comes to botany. I love learning about different plant families, how to identify them, common characteristics, and the wide and varied uses they serve. I can attribute this curiousity to two determining factors from my childhood: growing up in Michigan, where I would run around in communal backyards and plant marigolds each spring and watch as rabbits subsequently devoured them; and listening to my mother point endlessly to plants and be able to identify them by their common – albeit British – names. I was always slightly jealous of my mother’s knowledge, which she was miraculously able to retain from her primary school days, when British nuns considered nature-awareness a vital part of education.
Nevertheless, I have taken opportunities in my post-college life to fulfill my fantasies of becoming a “plant expert,” but if there’s one thing I’ve learned by living in the Bay Area, it’s that it is next-to-impossible to remember by sight the thousands of varieties that we are lucky enough to have the proper climate for. Plants act almost like markers; you can learn about a particular region by studying what is able to grow there; and the Bay Area’s temperate Mediterranean climate is apparently a favorite amongst plants.
John started by talking about trees, and their functions in an ecosystem. These are some of the hardest-working elements of a natural setting, providing shade, gas exchange, soil stability, the movement of minerals and nitrogen fixing. Nitrogen fixing refers to the presence of bacteria along a plants’ roots that intake other soil minerals and release, a highly volatile element that’s essential to the proper mix of carbon, nitrogen, potassium and phosphate in any good soil. Trees are covered with bacteria, epiphytes, oils, chemicals and other non-metabolic particles that perform several functions to increase the flow of minerals and energy in an ecosystem, providing the balance needed to weather systemic changes.
The benefits of trees have led botanists and horiculturalists to recognize the power of the forest edge, where plant species are more numerous, and encompass those that do well in forests as well as meadows. Here are generally stronger, hardier plants, because there are more variations in predators, pollinators and weather conditions. Agrofestry incorporated this idea, as well as recognizing that humans can mimic and add to natural processes by sustainably managing land, which has already been done by the earliest human inhabitants of any land area (and is also a permaculture principle). We now talk of food forests, where you take into account the wealth and bounty of trees, and learn what edibles can grow in that shade, feeding off those roots, benefit from that leaf matter or need particular elements that are found closest to trees. Particularly well-suited to food forests are certain plant nitrogen-fixers, including legumes, ceanothus shrubs, acacia and locust trees, and varieties of the broom family (which are unfortunately considered an “invasive” species by many – but that’s another discussion entirely).
By far, the most interesting plant characteristic we touched on was that of dynamic accumulators, plants that facilitate mineral release, and consequently, remediate soil. These plants include many “weeds,” such as dandelion, nettle, comfrey and sorrels – all of which are also edible. Next time you plan on digging up a particularly hardy plant, stop to think of its benefits – to both your garden and table.
