A tufted perennial plant with tall, upright stems (2) (3) (4), the spike trisetum (Trisetum spicatum) is a rather widespread yet little-studied species (4). The spike trisetum’s alternative common name, ‘downy oat-grass’, refers to the characteristic velvety hairs found on the stem and the flowering spike (4). On the stem, these hairs are typically fine, soft, short and sometimes matted (3), and are often curved forwards and upwards (2). The hairs are usually densest below the flowering spike, which is a loose, branching cluster of flowers, known as the ‘panicle’ (2) (3).
The panicle of the spike trisetum is short, dense and usually pale purplish-pink (4) (5) (6), although it may also appear gold-purplish to brown-purple (2). The branches of the panicle are short, and each spike contains two or three individual florets (tiny, individual flowers) (3) (6). The glumes, which are membranous bracts surrounding the spike, are usually shorter than the florets and are often unequal in size (2) (3) (5).
The lower bracts or flowering scales of the florets, known as ‘lemmas’, have a long, stiff bristle, called an ‘awn’, on the upper side, which is often bent and twisted. The lemmas are usually smooth, but curve and become rougher and more purplish towards the base (2) (4) (6).
The leaf blades of the spike trisetum are usually flat or rolled. They are either smooth or covered in very soft, fine hairs (2) (3), and the margins of the leaves are often bristly (3). The leaf sheaths of this species are also covered in fine, velvety or downy hairs (2) (3) (5).
The appearance of the spike trisetum varies greatly across its range. As a result, this species is often separated into numerous different subspecies and varieties, which has resulted in an extremely confusing taxonomy (2) (3) (7) (8).
- Stem height: up to 60 cm (2)