Designing for Disaster?

First, before I get rolling with this week’s blog from the Gardener on Main Street, I would like to offer a rarefied Happy Leap Day to all. Now for the main event: designing a garden for natural disasters.

My mother-in-law shared with me an Associated Press article which was published nationally a few weeks ago, and was picked up by some midwest papers. At first glance, there were a number of interesting points, but then some red flags arose. It is important when reading gardening tips and advice (including this humble blog) to consider the author and the author’s context (location). Most of what the author, and other experts quoted, discussed in this article applies to Florida and west coast states like California who deal with prolonged rain/high wind events (i.e. hurricanes) and wildfires annually.

As a quick aside, I would like to point out that I think of “design” differently perhaps than the standard use of the word in practice. Normally, the design of a landscape describes an early phase in building a garden, which then transitions to a maintenance phase with occasional upgrades down the garden path some day. “Design” in Wellfield/botanic garden terms describes the whole gardening experience and is a systems approach. Design refers to a cyclical process of creation, fostering growth, feedback and redesign, so when you are performing “maintenance” in the garden it is really a series of mini design decisions. You are designing the world around you all the time, thus most “failures” in the garden are design failures.

Okay, back to the article. My first “beef” with the article is the subject of the headline: plant selection. I would never “design” a landscape with natural disaster as my primary consideration when selecting plants. I would put greater emphasis on how different elements are arranged/interrelated within the design and how the plants are treated. The care and environment in which the design is installed is as, if not more critical, than plant selection criteria when it comes to resilience. For example, in a great University of Florida report discussing the effects of hurricane events on urban tree canopy survival, I noticed a good portion of the article focused on maintenance and environmental factors affecting trees and shrubs under severe wind/rain stress.

My second beef with the article relates to the first in that the author quotes an expert recommending native trees over exotics as a plant selection criterion. This is too broad of a generalization. Just because it is “native” to a region does not correlate with hurricane resistance. Plants have many different survival strategies, of which the biomechanics of the plant structure is only one. A native species might be ripped to shreds, but readily seeds as a means of preserving the gene pool, for example. Just because a plant is “exotic” does not mean it is any less likely to survive. Better to select plants based on their habitat of origins. If an exotic species evolved under high wind conditions naturally, it might be a good candidate. Critical thinking is required here.

As another aside, the article suggests planting species that lack flammable waxy coatings or resins, especially suggesting the avoidance of conifers. There is so much wrong with this, I hardly know where to begin. First of all, many pine species evolved in fire prone regions, thus they are naturally fire resistant. Second, selecting plants lacking waxy coatings is selecting species which might be less drought tolerant. Nothing like a dead, dried up plant to resist a fire, eh?

Just as important as plant selection is the plant’s function in the design. One could use microclimates to shelter a desired vulnerable variety. One should always consider a site’s dominant wind vectors just as one thinks about soil type, light levels and annual rainfall.

Another design strategy is to plant in groups, in resilient plant communities. Diversity and relational complexity are great ecological principles to utilize in natural disaster prevention. How plants are arranged is of greater importance than individual plant characteristics. I would look to arch-habitat types as inspiration for how to arrange plants to survive. How do forest or grassland species endure these types of extreme events? They survive working together, so draw inspiration from such models.

Beyond design considerations is plant care with respect to garden natural disaster prevention. Regular removal of dead and diseased limbs and whole plants is critical. Keep canopy trees properly thinned to offer the least wind drag. Give plants the needed root zone to grow. Make sure the garden is adequately watered, etc. Utilizing all the best practices creates naturally healthy, resilient garden plants.

The Midwest is less prone to fires and hurricanes, but strong wind, ice storms, flooding and drought are “disasters” we face. To help your garden weather any climatic extremes, incorporate swales, windbreaks, and plant communities in your design decisions, along with good plant selection, for best results.

Josh Steffen, Horticulture and Facilities Manager

9 thoughts on “Designing for Disaster?

  1. This topic comes up often in rural and many suburban regions of California. Some landscape designers prefer natives. Some prioritize the potential for combustibility. The problem is that there are not many natives that are not combustible. Redwoods happen to be one of the few species that survive fire by not being combustible. What is not often discussed is that there are many species that are not only combustible, but are ‘intentionally’ combustible. That means that they try to make themselves as combustible as possible to incinerate the competition. California fan palm accumulates long beards of dead fronds that burn very hot and very fast. They survive, but incinerate the red willows and other species that share their riparian oasis in order to make more real estate available to their seed, which also survive fires. Monterey pine also accumulated dead debris to be more combustible, and then open their cones to disperse most of their seed as they burn to death. In landscapes, such trees need to be groomed of combustible material. So, yes, they know how to survive fire (although the pines die in the process), but they want to burn everything around them! Most exotics are less combustible than the natives. Unfortunately, we do need to design for fire in rural and suburban regions. It is part of living here.

    1. Thanks for providing a perspective from southern California, Tony, we appreciate that Josh’s blog helps to stir conversation so far away thanks to the world wide web! These are important discussions everywhere, with each particular region needing to consider their particular circumstances. Thanks for being a part of the conversation!

      1. I am actually in Northern California, but such issues are common in various places here. They are regionally different of course. When I work in some parts of Southern California, the concern for combustibility is not the same. Have you seen the Mojave Desert? There is not much to burn out there. If the California fan palms burn, no one minds. It is actually good for them. In my neighborhood, there is not much that we can do about the surrounding forests. Redwood forests are safer than pine forests of course. In town, just a few miles away, there is no concern about combustibility. Obviously, we must keep cypress and pine trees clean; but otherwise, landscaping is not limited by the potential for fire. I suspect that is how it is in most places.

      2. I’d recalled a photo you’d sent of your street some time ago (of a not-so-good pruning job) and mis-identified the landscape as being SoCal, where I’d spent about 5 years at another public garden in Claremont CA

      3. Oh, ‘that’ picture! It was the remains of a tipu tree on South Orange Drive, two blocks west of South La Brea Avenue, just north of the Santa Monica Freeway. It really is in Southern California.

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