A field experiment was conducted in order to investigate the seasonal changes of leaf growth and related characteristics in three cultivars of orchardgrass; Potomac, Kay and Sumas. The results were summarized as follows: 1. Leaf elongation was increased in a nearly linear phase during first and third cutting stages. It was increased slowly in early 10 days to 15 days after cutting and increased rapidly thereafter during the rest cutting stages. In cultivars, Potomac was showed hlgher leaf elongation than other cultivars during all cutting stages. There was no difference of leaf width within cutting stages, but the leaf width of fall regrowth was narrow. Sumas had relatively short and wide leaves. 2. Leaf dry weight and leaf area in first cutting stage were larger than others. Leaf area was increased rapidly from 15 days after cutting and leaf $we$ was increased rapidly from 20 days over all cutting stages. The increase in leaf area and dry weight were slow down after 30 days. 3. Number of epidermal cells was increased rapidly after cutting and the rate of increase was slow down after 30 days. In a cross section of leaf tissue, the part of mesophyll was occupied with about 60% of total area and larger area than other tissues. Leaf tissue had a large vacancy at early growth period after harvest and was filled gradually with mesophyll. This result was related to the increase of leaf dry matter.