Rhododendrons are one of the most popular woody garden plants. They are prized for their showy flower displays and ease of care. Many rhododendrons are capable of surviving very low temperatures in the winter.
Rhododendron leaves are oval shaped, about 1- to 2 1/2-inches long and are usually dark green. Often the leaves turn a reddish color during freezing winter temperatures.
Like most leaves, they consist of an outside epidermal layer on top and bottom, palisade mesophyll and spongy mesophyll layers where the chlorophyll is, and veins for transporting water and nutrients.
The primary purpose of a leaf is food production for the plant using photosynthesis. Leaves also exchange oxygen, carbon dioxide and water with the outside air.
When grown in shade the leaves tend to be larger and thinner to gather more light. Leaves grown in full sun are smaller and thicker to retain moisture.
Thermonasty is the process of plant movement triggered by changing temperatures. In extreme cold, the leaves of some rhododendrons curl to create a slightly more humid atmosphere under the leaf and to deflect excess sunlight that would normally burn the plant.
- P.J.M. Rhododendron
- Structural Adaptations in Overwintering Leaves of Thermonastic and Nonthermonastic Rhododendron Species
- The Leaf
- The American Rhododendron Society
thermonasty, photosynthesis, winter rhododendron
About this Author
Brian Albert has been in the publishing industry since 1999. He is an expert in horticulture, with a focus on aquatics and tropical plants like orchids. He has successfully run an aquatic plant business for the last five years. Albert's writing experience includes the Greater Portland Aquarium Society newsletter and politics coverage for a variety of online journals.