I have three patches of ostrich ferns that are three years old and seem healthy. But this year many of the plants are shorter and more squat (spreading low instead of tall) than in previous years. Some of the plants on the outside of the plots, although apparently well established, are small and almost stunted, for ostrich ferns.
Any suggested reasons?
Height varies with the amount of moisture and nutrients the clumps can access. When located in cool-Summer climates, and growing in rich soil that is downright moist or even boggy in Spring, and never less than moist the rest of the year, fronds can top five feet. In more typical garden conditions—average soil and water in part or full shade—expect fronds to be two to three feet high. There is less variance in the height of the fertile fronds: sixteen to twenty-four inches. In ten years, a single starter plant could expand into a colony ten feet across or more.