Washingtonia robusta (Mexican fan palm) HPWRA Score: 15 High Risk
Impact: The fast-growing can palm quickly becomes a hazard when exposed to windy weather. The frond skirt is a fire hazard as well as a suitable habitat for rat nests. The palm tree is self-compatible, forms dense thickets and is shade tolerant. One study counted the viable seeds produced by this tree and found an average of 560, 345 seeds per tree!
Description: Native to Mexico, this fan palm can reach heights up to 100 feet. The fronds are fan-shaped as the common name suggests. The frond stems or petioles are sharply toothed, this is one way to tell this palm from the native loulu palms. The fronds persist for years, hanging on to the crown long after their color turns from green to brown. The “frond skirt” or “petticoat” is a tell-tale way to identify this tree. There are often 30 fronds in a healthy canopy. The inflorescence (flower clusters) are up to 9 feet long containing small orange-pink flowers. The fruit is a small black drupe that has a thin coat. It has a nice appearance when young, however, it looks like a “telephone pole with small tufts a small fronds” when old. They are often found invading glutches on Hawaii island.