Reducing the risks of fire in gardens: understanding the flammability of different plant species

The recent devastating wildfires that occurred in Hawaii this month were, in part, exacerbated by the presence of certain plant species, specifically invasive grasses that have overtaken areas previously inhabited by sugar and pineapple plantations.

These wildfires, characterized by their destructive nature and widespread impact, have ignited a discussion on the environmental consequences of invasive species and their contribution to the intensification of natural disasters.

The takeover of land once dedicated to sugar and pineapple cultivation by these invasive grasses has not only altered the ecological balance of the region but has also created highly combustible fuel for wildfires.

This unfortunate situation highlights the need for comprehensive strategies to manage and mitigate the spread of invasive species, as well as the importance of sustainable land management practices to prevent future catastrophic events.

According to Michele Steinberg, the wildfire division director at the National Fire Protection Association, it has been observed that certain plants have a higher susceptibility to catching fire compared to others.

However, it is important to note that there is no plant that can be considered completely fireproof. Regardless of the type of plant, under the appropriate circumstances, all plants have the potential to ignite.

The crucial factors contributing to the ignition of plants include improper pruning techniques, inadequate watering, and substandard sanitation practices that result in the accumulation of dry and dead plant material on the soil surface, particularly in areas prone to high fire risks.

Therefore, it becomes imperative to understand and implement proper plant care procedures to mitigate the risk of fire incidents.

Living in a fire-risk zone or an area where climate change is intensifying the fire risk requires careful consideration when selecting plants for your garden.

Understanding the fire resistance of different plant species and their flammability can greatly benefit you in creating a safer environment.

By choosing plants that offer some level of fire resistance, you can significantly reduce the risk of fire spreading and potentially protect your property and the surrounding area.

Conversely, selecting plants that are highly flammable can increase the vulnerability of your garden and pose a greater threat in the event of a fire.

Therefore, it is crucial to be well-informed about the fire characteristics of various plants to make informed decisions and mitigate the potential dangers associated with living in a fire-prone region.


Plants that possess aromatic oils, resins, waxes, or gummy sap are highly susceptible to catching fire quickly, regardless of being well-watered and nurtured.

Some of these plants include acacia, bamboo, eucalyptus, Japanese honeysuckle, rosemary, Scotch broom, and gas plant, which earns its name from the flammable vapor released by its flowers and leaves.

In comparison, trees with peeling and papery bark, such as river birch, tend to be more easily ignited than those without such bark.

Additionally, evergreen shrubs and trees with fine needles, such as cedar, cypress, fir, juniper, pine, and spruce, contain volatile saps and resins that contribute to their flammability.

The risk of fire further increases when their dropped needles are left to dry on the ground or accumulate on roofs. However, redwoods stand out as an exception to this pattern, as their bark’s high tannic acid content makes them fire-resistant.

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Many grasses, such as buffel, molasses, and guinea types, along with fountain and feather grasses, are deemed highly susceptible to fire.

These grasses played a major role in fueling the devastating fires in Hawaii. Their flammability is further exacerbated when they are left to stand dry over winter or during periods of drought.

The excessive dry heat during these times causes the moisture in the soil and in these grasses, as well as many other plant varieties, to evaporate rapidly.

This process essentially transforms these grasses into easily ignitable kindling, posing a significant fire hazard.


As a group, “native plants aren’t necessarily less flammable” than introduced species, as stated by Steinberg. However, it is important to highlight that nonnative, invasive plants often present higher fire risks due to several factors.

These plants have a tendency to rapidly spread, usually without being disturbed by wildlife. Additionally, they outcompete native vegetation and are capable of tolerating extreme weather conditions such as heat, drought, and heavy rains.

This adaptability allows them to cover vast areas of land, spanning from fields to acres and even miles. Consequently, a mere spark, such as one ignited by lightning, has the potential to set these invasive plants ablaze, posing a significant fire hazard.

For the best fire resistance, it is recommended to choose deciduous trees such as ash, crabapple, dogwood, locust, maple, and oak over fine-needled evergreens.

Deciduous trees shed their leaves during the winter, reducing the amount of flammable material present. In contrast, fine-needled evergreens, such as pine and spruce, retain their needles throughout the year, making them more prone to catching fire.

Another option for fire-resistant landscaping is to incorporate succulents with water-filled leaves, like ice plants and sedums.

These plants have evolved to store water in their leaves, making them less flammable. In the event of a fire, succulents can release moisture from their leaves, which helps to resist ignition and slow down the spread of flames.

In addition to trees and succulents, certain groundcovers can also contribute to fire resistance. Ajuga and creeping phlox, for example, are known for their low-growing, dense foliage that can act as a natural barrier against fire.

These groundcovers create a thick layer of vegetation that can prevent fire from spreading quickly and reduce the risk of ignition.

When planning for fire-resistant landscaping, it is important to consider the overall layout and arrangement of plants.

Creating defensible spaces by spacing plants appropriately and removing dead or dry vegetation can further enhance fire resistance.

Additionally, regular maintenance practices such as pruning branches away from structures and keeping the landscape well-watered can help minimize the risk of fire damage.

Overall, by selecting deciduous trees, succulents with water-filled leaves, and fire-resistant groundcovers like ajuga and creeping phlox, homeowners can create a landscape that is more resilient to fire incidents.

Implementing these suggestions, along with proper maintenance and fire safety measures, can significantly reduce the potential for fire-related damage to properties.


The Washington State University Extension Service has recently released a comprehensive set of guidelines that highlight the key characteristics of plants that are resistant to fire.

These guidelines serve as a valuable resource for individuals looking to create fire-resistant landscapes.

One of the primary characteristics identified by the guidelines is a high moisture content in the leaves of plants.

This moisture content plays a crucial role in reducing the risk of ignition and slowing down the burning process. As a result, plants with higher moisture levels in their leaves are considered to be more fire-resistant.

Another important characteristic is the absence or minimal accumulation of dead vegetation throughout the different seasons.

By ensuring that there is little to no build-up of dead plant material, the risk of fire spreading rapidly is significantly reduced. This emphasizes the importance of regular maintenance and removal of dead vegetation from the landscape.

Plants with open branching habits are also highlighted as being more fire-resistant. The open structure of these plants provides less fuel for fires, making them less susceptible to ignition and subsequent burning.

Additionally, having fewer total branches and leaves further decreases the amount of fuel available to a fire, consequently lowering the risk of rapid spreading.

Furthermore, the guidelines emphasize the significance of selecting slow-growing plants. By opting for slow-growing varieties, homeowners can minimize the need for frequent pruning.

This is essential to maintain the open structure of the plants, which in turn contributes to their fire-resistant nature.

Lastly, the guidelines underline the importance of non-resinous material on plants. This refers to stems, leaves, or needles that do not contain resin, oil, or wax. Such materials are less flammable and therefore reduce the risk of plants catching fire easily.

In conclusion, the guidelines provided by the Washington State University Extension Service offer valuable insights into the characteristics that make plants fire-resistant.

By considering factors such as high moisture content in leaves, minimal accumulation of dead vegetation, open branching habits, fewer total branches and leaves, slow-growing nature, and non-resinous material, individuals can make informed choices when selecting plants for their landscapes.