Normal vs. Abnormal Needle Drop or Leaf Drop from Evergreens Nondeciduous plants normally retain their leaves for several years but eventually they fall. This drop is usually gradual and production of new leaves obscures loss of older leaves. Unfavorable growing conditions, such as drought, may accelerate leaf fall so that it becomes apparent and of concern. Drop of current year's leaves may result from pathogen or insect attack or from chemical deficiencies or toxicities. Always compare the typical diseased plant with a healthy or normal plant, since normal plant parts or seasonal changes are sometimes mistakenly assumed to be evidence of disease.
Examples are the brown, spore-producing bodies on the lower surface of leaves of ferns.
These are the normal propagative organs of ferns. Also in this category are the small, brown, club like tips that develop on arborvitae foliage in early spring. These are the male flowers, not deformed shoots. The leaves of some plants, such as some rhododendron cultivars, are covered by conspicuous fuzz-like epidermal hairs. This is sometimes thought to be evidence of disease, but it is a normal part of the leaf.