"Deciduous or evergreen cotoneasters (Cotoneaster spp.) grow as dense groundcovers and as shrubs that grow up to 25 feet in height. They're suitable, depending on species, for U.S. Department of Agriculture plant hardiness zones 4 through 9. A few have become invasive in Mediterranean climates, and most are grown for their dazzling -- but toxic -- red or orange fall berries..
"The California Poison Control Center lists cotoneasters as Level 4 toxic plants. Ingesting their poisonous parts affects the heart, liver, kidney or brain. Cotoneasters' leaves, berries and flowers all contain cyanogenic glycosides. These toxins convert to cyanide during digestion, but cotoneasters' low concentrations of them mean an adult would have to eat a large amount to suffer serious symptoms. For pets or children, however, the risk of a serious reaction is much higher."