When is being green not the same as sustainability?
Autumn olive is an example of a woody invasive plant that is green into the fall.
Invasive species of plants in our area were many times brought here for landscape and garden qualities that allow them to outcompete native varieties.
Maturing earlier, prolific flowers and fruits or seeds, and staying green longer into the fall are qualities that allow invasives to take hold and overcome native plants. Autumn olive (Elaeagnus umbellata) and Russian olive (Elaeagnus angustifolia) are two common examples of woody invasives in our area that are green into the fall.
Their edible fruits are widely spread by birds and animals, and their longer growing season allows them to outcompete native plants. Japanese honeysuckle (Lonicera japonica) and Morrow's or bush honeysuckle (Lonicera morrowii) similarly have longer active periods of green than native plants and flowers that are crowded out.
Honeysuckle has been sold for landscape plantings, but rapidly spreads. It has been observed that the red dye in honeysuckle berries contributes to darker orange coloring of tail feathers of cedar waxwings feeding on the berries.
These and other invasive plants take advantage of allelopathy, the release of small amounts of chemical compounds, mainly from root systems, which retard the growth of nearby plants. After the first hard frosts in our area, deciduous native trees and shrubs will have lost their leaves and most other native plants will have died back and turned brown. Late fall is a good opportunity to identify invasive species for control, as most of the plants remaining green longer will have taken hold from other parts of the world.
Nature Notes for 11/20/2011