Glyceria grandis (American Manna-grass) in Surrey
Glyceria grandis S. Watson (American Manna-grass) in Surrey GEORGE HOUNSOME
I
n August 2019 I was exploring Squires Great Wood, an area of mixed Forestry England woodland north of Coldharbour, Surrey (v.c. 17). I came across a small pond (at grid reference TQ147461) with evidence of planting in the dim and distant past, and at one end was a small patch of a fruiting grass that I didn’t recognise. The tallest culms were approaching a metre in height and the panicles, although occupying a lot of space, were extremely diffuse with tiny spikelets, more so than any grass of that size that I’d seen before. Most of the spikelets were empty, with only the glumes remaining, but the lemmas of the few remaining ones were just over 2 mm long with seven prominent veins. A few florets were occupied by small black bodies which I incorrectly took to be caryopses, but more of that later. I assumed it was an established planting, took a few photographs and a piece to take home to try 48
BSBI NEWS 146 | January 2021
Plate 1. Glyceria grandis (American Manna-grass) en masse at Great Squires Wood, Surrey, June 2020. Photographs by the author.
to name it and moved on. A few hundred metres to the north, by a narrow ditch in woodland, where it certainly would not have been planted, I found another patch, so I revised my assessment of its status to ‘naturalised’. I still had no idea even which genus it might be, but after several phone calls to Eric Clement, sending him a specimen and following up likely suggestions we arrived at Glyceria grandis S. Watson (American Manna-grass), native to North America and Canada. Indeed, the wet habitat and the shape of the leaves, parallel-sided narrowing towards the tip, was characteristic of the genus. It was once listed in the RHS Plant Finder but not since 1997, so as it was probably introduced
