THE USE of xerophytic plants, which are drought adapted plants, is an increasingly popular topic in the gardening world, and a timely subject to consider during a summer of water shortages and forest fires. Contrary to popular belief, xerophytes are not found in deserts. Virtually all drought tolerant plants come from areas that receive at least some rainfall, even though it may be very irregular in some places.
Plants from the semi-arid regions of the world cope with low rainfall and high temperatures in a variety of ways, but the most common, and obvious, is through the storage of water in the roots, stems or leaves. These tissues absorb water and swell, and it is this succulence that can make these plants valuable in the case of fire. Because they are full of water, they are known as fire retardant, which means that when planted strategically in the garden, they are more difficult to ignite. They can slow the approach of a fire and lessen its intensity by releasing the water stored in their tissues.
Cacti are probably the plants that spring to mind, but there are a huge number of succulent plants of all shapes and sizes. If you look around, you will see a number of succulent plants that are naturalised in the Mediterranean, even though they come from different parts of the globe.
A collection of cacti, planted in well drained soil and mulched with gravel, are a fascinating and fire safe feature. Cacti are found in many habitats ranging from rainforests, like the Epiphyllums with their arching, flattened stems and fantastic huge flowers, to species like Echinocereus viridiflorum and other mountain cacti, which are winter dormant and may spend most of that season under a covering of snow!
All of the cacti originate in the Americas, where the hardiness of some species of Opuntia mean that their range is from Canada to the southern parts of South America. All other cacti, even those that are naturalised in other parts of the world, are introduced.
Succulents and plants that have fleshy leaves are not the only plants with a degree of fire retardance. Plants such as the familiar cork oak (Quercus suber) are adapted to survive fires by having a thick protective bark. This is also a feature found in several unrelated Australian trees.
Fire retardant plants are commonly confused with fire resistant plants. A fire resistant plant is simply a plant that has some strategy for surviving fires. Many are extremely flammable, as this helps them to wipe out their competitors. Gorse, gum cistus (cistus ladanifer) and medronho (Arbutus unedo, the Strawberry tree) are all very common and flammable species. The introduction of eucalyptus on a commercial scale is nothing short of an environmental disaster when added to this cocktail of flammable native plants. Beware of growing any of these species near to your home!
The subjects of fire resistance and fire retardance in plants are covered extensively in my CD-Rom, Gardening with Fire. There are numerous profiles of plants to cherish, and those to avoid!
