The occurrence and growth of elongated aerial stems of browntop (Agrostis tenuis) were measured in hill pastures under low fertiliser input and pasture utilisation (LFLU), and under high fertiliser input and pasture utilisation (HFHU). Aerial stems grew rapidly from December until April, more so in the LFLU swards than in the HFHU swards. Under LFLU, up to 30% of tillers sampled after the end of December originated from a node on an aerial stem. Under HFHU, the maximum value was 12%. The formation of tillers at nodes on aerial stems occurred throughout the study (from July until the following May), but at a low rate in late spring and most rapidly in early summer. Where grazing pressure and fertility levels are inadequate to suppress aerial stem development, short-term grazing managements are likely to provide only limited control of rank browntop growth.

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