Fenugreek is one plant often used as a cover crop as well as a substitute for alfalfa. It is a fast-growing legume that reaches about 2 ft. in height (60 cm) and as its botanical name suggests, it is often used as a hay substitute. It is favored by those who wish to promote milk production in dairy animals or improve the sheen of feathers and fur.
Fenugreek is an annual and is only cut once a season but it produces more than alfalfa and is frost tolerant when planted early.