Root-crown temperature has been found to affect plant growth and physiology in a number of ways.
[1] Root crowns need to be exposed and 'breathe'; this is one way that some plants take in oxygen.
A number of pests and diseases affect specifically this part of the plant, including root-crown rot (or root-crown fungus)[2] and a number of species of root-crown weevil.
The root crown area usually appears swollen, tapered, constricted or very thin - as well as a combination of these.
The area of the root crown is usually located around or at the soil level and can be vaguely or clearly apparent.