Quercus is a large genus with around 600 deciduous or evergreen trees and shrubs, also known as Oaks. These are popular trees for their foliage, growth habit and in some species, attractive autumn colour. Foliage is arranged in spirals and leaves are distinctively lobed, with serrated or smooth edges dependent on species. These species are monoecious, and thus produce male and female flowers on the same individual. Male flowers are yellow and arranged on catkin structures for optimal wind dispersal of pollen to female flowers, which are small and bud-like with feathery, divided stigmas. They are followed by the very distinctive acorns - small, ovoid brown nuts held in scaly half-cup structures. Oak trees are often seen in the countryside in the Northern hemisphere or grown as specimens in large gardens or parks. The foliage and acorns are toxic to dogs.