Flowers are not exclusively unique to the spring but they are most plentiful during this time. Some of my personal favorites are the less glamorous blossoms on trees and underbrush, as they are unique in shape and color.
One such example are the flowers of the Tulip Tree which sport bright yellow-green petals with an orange V at the base. This is a very maleable material and I've used things like this in a number of different installations.
All art and photography by Ned Carlson