Q: I’ve heard Arundo grass is invasive, can you tell me more about it? — Teresa Rhatigan, San Luis Obispo
A: Tall, robust and showy, Arundo donax, or giant reed, may seem like an ideal plant to encourage in your garden. With long green leaves that approach 30 inches in length and a height of up to 30 feet, this statuesque plant evokes the image of aswaying dancer.
Similar in habit to bamboo, Arundo donax grows on a long canelike stem with a diameter of up to 4 inches. This perennial flowers during summer months. The flower is a long, purplish plume that grows from the top of the plant. The variegated version is particularly attractive. Arundo is the largest nonnative grass that grows outside of the tropics. One look and you may find yourself starstruck.
But, before you fall head over heels for this easy-growing grass, it may be wise to keep in mind the old adage, “Looks can be deceiving.” Beneath the lithe appearance of the Arundo donax lies a plant capable of invasion so thorough that native plants don’t stand a chance once confronted. Arundo plants reproduce via rhizomes and root systems often form dense mats that may span many acres underground.
The plant thrives in moist soils that are nitrogen rich. They prefer ample sunlight. Rivers and creek beds are notorious hangouts. Large amounts of water do not deter the incalcitrant Arundo. In fact, during episodes of flood, plant segments become dislodged and serve to renew growth by rooting in a new location. It is in this way that Arundo has a significant advantage over other native growth.
Under circumstances ideal for growth, the Arundo dominates all other plant life. Wildlife that depends on a habitat that combines diversity and natural complexity have little use for this plant, which provides no suitable food source.
The Arundo does not stop there, however. Highly flammable, the Arundo ignites quickly, spreading wildfires and allowing them to “jump” water sources that would ordinarily serve as a barrier. Once burned, the Arundo grows back significantly quicker than other plant life, increasing its odds of proliferation.
The invasive nature of the Arundo has placed it on the top 100 list for most invasive plant species.
Eradication of this plant takes many forms depending on the severity. Use of mechanical methods to dig plants out and Roundup (glyphosate) are two methods for dealing with this highly invasive grass.