Use the above link if you already have iTunes installed. Or, go to the Apple iPhone app store and search for SM Invasives. Note: the iPhone currently only works with the Santa Monica National Recreation Area.
Navigating to http://WhatsInvasive.com on your Android browser will also get you to a download page direct to your phone. The Android app works with all participating parks!
Yellow Starthistle is an annual to short-lived perennial herb, ankle to shoulder height and generally mounded with many branching stems - particularly when tall. Leaves are gray-green, slightly downy (minute hairs on surface), alternate and either simple or partially lobed. Flowers are yellow, characterized by having sharp, rigid spines around flower heads. Generally blooms during the summer months. Only reproduces by seed. More