All plants will burn under the right conditions, regardless of how they are classified (“fire resistant”, “fire safe”, “firewise”, etc). Growing conditions and maintenance can have a greater impact on the flammability of plants than the species itself. You can create a fire-resilient landscape by following these three simple concepts:
- Right Plant, Right Place
Right Plant, Right Place
Besides taking into account the plant's physiological needs (water amount, sunlight tolerance, soil properties, etc), this theory also considers the surrounding landscape, such as buildings, fences, sheds, or patios. For example, closer to Zone 0 a small or slow-growing shrub would be more appropriate than a large one. In a drier or stressed environment, a plant may have stunted growth and accumulate dead parts, while one with a good water supply will have a strong growth and hold leaves for a longer period of time. This can result in the same species being fire-resilient in one environment and very combustible in another.
Here are some questions to consider when selecting plants for your home:
- Does this plant shed bark, leaves, flowers, etc.? What time of year does the shedding occur? A plant that sheds bark or branches is likely to need more regular maintenance-related cleanup to reduce fuel accumulations on the ground. A plant that has a big leaf or needle drop will result in the need for more maintenance-related cleanup on the property, on the roof, and in rain gutters
- How dense are the foliage and branches, especially closer to the ground? A plant that is more densely structured can capture embers and may be more likely to ignite. It will also be more likely to be easily ignited from a surface fire.
- What are the water and sunlight needs for the plant? How fast does the plant grow? A plant that grows quickly may exceed growth expectations and require greater maintenance.
- Does the plant have waxes, oils, or resins? A plant with more waxes, oils, and resins will likely be more flammable and release more energy when it burns.
Native plants, pollinator friendly, or drought-tolerant plants can be good choices for those labeled qualities, but these features don’t directly translate to fire-resistance.
By increasing the spacing between plants and groups of plants, a fire can be limited or stopped from spreading. Plant spacing includes both horizontal and vertical clearance between plants, as well as between plants and structures. Walking paths and gravel areas can be used between groups of plants to increase their spacing.
Whether a plant ignites depends more on pruning, maintenance, and cleanup than on what type of plant it is. Some plants, such as lavender, may initially have lush, non-woody growth, and then several years later become woody and choked with dead material. Other plants may develop a dead thatch layer under a green surface that is highly combustible.
- Prune plants to provide horizontal and vertical space throughout your garden and surrounding structures
- Clean the understory of plants and trim the branches closest to the ground
- Irrigate plants appropriately
- Plants with big leaf or needle drop may result in more maintenance