May 15, 2005

Welcome PC Activist Readers

Hi there...if you came to us via Rich's article in the new issue of Permaculture Activist, welcome! Take a look around at our general farm offerings on the links to the left, or check out the categorized blog posts (with farm pictures) via the links to the right.

Thanks to Robert for correcting my Coast redwood vs. Giant Sequoia Latin...I've never been able to keep those two straight....I corrected it below.

And for those of you who have been regulars, and have no idea what I'm talking about, the text of the article follows....

The Straight Overstory

The art/science of plant guild design is still a young, exciting field. Like language, where 26 english letters spawn millions of meaningful words, our plant “alphabet” is very large, and now the work begins to start creating connections between soil, light, and water preferences in order to create systems that are self-sufficient and productive.

A feature of guilds that is often glossed over is the physical and structural characteristics of the component plants, as opposed to just the biological requirements. Here I’d like to talk about some of the benefits of bringing this additional layer of information into our designs.

Despite popular perception, the Willamette Valley of Western Oregon isn’t as wet as the stories tell. While Portland receives around 35” of rain per year, the vast majority of that falls from October to March, outside of the main growing season. The landscape shares a lot of characteristics with California; a glance in August at the shimmering, golden hillsides studded with oaks brings Steinbeck to mind far more than Sometimes a Great Notion.

When my wife and I moved to Mossback Farm’s new location in 2002, I behaved much like Toby Hemenway did when he moved to his rural property in southern Oregon (PCA 55). Grand plans, and a fair bit of cash, went into plantings that would give us yields far into the future. I could see the chestnut, walnut, and locust forests, productive understories, interspersed with pastured poultry and ruminants to cycle nutrients. A completely integrated plant-animal polyculture guild. It was going to be perfect, of course.

This vision took a beating early the following summer. Unseasonably hot weather settled in by early June, and the summer baked until it broke with a blessed early rain in September. Our water supply wasn’t fully developed yet, so 5 gal buckets, sweat, and cursing were the watering norm. While only a few plants died, I fear that more than a few of them will be permanently stunted due to early suffering.

After that first summer, I stepped back to evaluate what I could do to make the situation the following summer more tolerable. I expanded the rooftop catchment system, increased the pipe network out to the planting areas, and redoubled my mulching, composting, and organic matter efforts. But the biggest lesson I learned in this time was the effect that existing trees and shrubs had on the surrounding landscape.

In the shade of each of the young evergreen trees (mostly Noble Firs & Willamette Valley Ponderosa Pine) planted by the previous owner, the grass would grow lusher, staying green later into the summer and greening up earlier in the spring. As the winter progressed, an ice storm swept through, and again, the areas under the trees told a story. When everything started to thaw, the area around the trunk would clear of ice first, due to both heat gain and drip from the canopy.

Other climates have parallel lessons that we can apply here, as well. Sagebrush (Artemesia spp) is a deep rooted desert and shrub-steppe species common to the Intermountain West. It can gather water from deep in the subsoil in order to survive. During the brief desert green season, annuals form a carpet of green immediately beneath the sagebrush, buffered from the elements by the small, but still effective canopy of the plant.

The California Coastal Redwood (Sequoia sempervirens) ecosystem is one that is highly dependent on the existing tree canopy to sustain itself. One needs to only compare adjacent drainages, one with recent timber harvest, and one with existing old growth trees, to see this fact. In the absence of the canopy, the harvested area bakes in the summer sun, killing any seedling Redwoods that are present. Gorse invades, getting a jump on any useful or native species due to its nitrogen fixing traits. It creates impenetrable thickets, making future reclamation of the land that much more unlikely. Meanwhile, just one valley over, the old trees gently hold the sea mist that blows in, and gives comfort to the sensitive seedlings that will eventually grow to replace the existing giants of the grove.

Even the cursed Scotch Broom, a noxious weed of which Mossback Farm is endowed with an abundance, has some beneficial effects. Like the conifer understory, the areas under the broom remain green and lush for much of the summer, unlike areas just a few feet away outside of the canopy. Some of this effect was undoubtedly due to the nitrogen-fixing properties of the broom, but the buffering characteristics of the canopy are also to be credited.

We are taking advantage of this “Scotch Broom effect” by clearing a patch and planting useful trees in the shade of the remaining broom. They will benefit from the shade and nitrogen until they become established, upon which we will remove the broom. This mimics ecological succession, making less work for us.

Normally, temperate permaculture design doesn’t have much use for evergreen trees in zones 1 and 2, since only rarely do they have a crop that is 1) harvestable and 2) needs continuous care throughout the year. However, in this landscape, we are finding that using evergreens, and conifers in particular, benefits the design in two ways. First, a suntrap can be created, which will cut the cold north winter winds and help to hold more winter sun. Secondly, the conifers, through both shade and condensation (fog drip), as well as the shed needles that they contribute to the soil, are the overstory that contributes to a shrub layer that can be very useful and productive. Currants(Ribes spp), blueberries (Vaccinium spp), raspberries (Rubus spp), and cranberries (highbush – Viburnum and lowbush – Vaccinium) are natural conifer understory plants, being acid- and shade-tolerant. Thus, all are excellent candidates for rounding out this guild.

This expands somewhat on the existing guild concept, since the conifers are contributing more of their physical characteristics to the system, rather than an actual harvestable yield. However, a passive yield of better growing conditions, one that doesn’t have to be managed after the initial investment of time and energy, is very much the foundation of a sustainable permaculture system.


Posted by rich at May 15, 2005 02:23 PM