Cushions, mats and rosettes: plant forms
The main growth forms of high-ground plants, cushions, mats, rosettes and tussocks, with the features that separate them in the field.
A growth form is the overall shape a plant takes: how tall it stands, how it spreads, and how its stems and leaves are arranged. Growth form is often the first feature a reader notices, and it narrows the search before flowers or leaves are examined closely.
Why form comes first
Many high-ground plants flower for only a short time, and a flower may be absent when a visit is made. The shape of the plant stays visible for longer, and it places a plant in a group before the details are checked.
The main forms
- Cushion plant
- A dense, rounded mass of many short stems and small leaves, often flat-topped and firm to the eye. Its outline is even, with few stems standing clear of the mass.
- Mat plant
- A low, spreading plant with stems that run along or just above the ground and root where they touch the soil. It forms a loose sheet rather than a dome.
- Rosette
- A cluster of leaves arranged in a ring at ground level, with the leaves radiating from a centre. A flowering stalk, if present, rises from the middle.
- Tussock
- A tuft of grass or sedge with leaves and stems growing from a common base and standing upright.
- Prostrate
- Lying flat along the ground. The word describes a habit that several of the forms above can share.
Cushions and mats compared
Both forms keep close to the ground, but a cushion is domed and dense while a mat is spread and open. Look at the edge without touching the plant. A cushion has a clear, rounded boundary, while a mat has stems that reach out past the main body. The contrast is explained further in telling a cushion from a mat.
Rosettes in the field
A rosette is easiest to read from above. Note whether the leaves lie flat or rise, whether the ring is open or tight, and whether the centre is bare or holds a stalk. These details separate many similar-looking plants that share a low habit. The leaves themselves are covered in reading the leaf rosette.
Other forms
Tussocks, dwarf shrubs and herbs with upright stems also grow above the treeline. Dwarf shrubs are woody plants kept low by wind and cold, and from a distance they can look like cushions. Woody stems, when they can be seen without disturbing the plant, separate them.
Telling forms apart in the field
- Note the overall height of the plant above the ground.
- Note whether the plant is dome-shaped, spreading or radiating from a centre.
- Note whether the stems are woody, soft or grass-like.
- Note whether the edge is clear or ragged.
- Note the ground the plant sits on, such as stone, grit or moss.