There are a total of 24 rare plant species and two unique trees: the Bristol and Wilmotts's whitebeams.[55] Other notable plants include Bristol Rock-cress,[56] Bristol onion,[56] Spiked Speedwell,[57] Autumn Squill[57] and Honewort.[58][59] Other areas along the river which have this designation include Bickley Wood,[60] Cleeve Wood, Hanham for its large population of Bath Asparagus (Ornithogalum pyrenaicum).[61] Stidham Farm near Keynsham contains at least At least 2 metres (7 ft) of Pleistocene terrace-gravels, consisting of limestone clasts mainly, but also with Millstone Grit, Pennant Sandstone, flint and chert clasts.