You can often recognise a melastome without knowing the species, or even the genus. The family has a small set of reliable features. Learn them, and you will start noticing melastomes in botanic gardens, forests and nurseries.
Clue one: the leaf veins
The most useful clue is leaf venation. In most melastomes, several prominent veins run from the base of the leaf towards the tip, curving in an arc, and are linked by many fine cross-veins, rather like the rungs of a ladder. Botanists call this acrodromous or longitudinally parallel venation. Most commonly there are three, five or seven main veins, which is why the "three-vein rule" is a popular shortcut.
To check, hold a leaf up to the light. Look for veins that start together at the base and sweep towards the tip, with ladder-like cross-veins between them.
Clue two: opposite leaves
Leaves are usually in opposite pairs, with each pair at right angles to the pair above and below it. Stipules, the small leaf-like appendages at the leaf base seen in many other families, are generally absent.
Clue three: hairs and scales
Many melastomes are covered in hairs, bristles or scale-like structures, giving the leaves and stems a rough or velvety feel. In some, such as Clidemia hirta, the hairiness is obvious.
Clue four: the flower
Flowers offer a second set of clues, covered in detail in the anatomy of a melastome flower:
- Four or five petals, though some have three (Sonerila).
- Stamens often twice as many as petals, with curved appendages.
- Anthers opening through a pore at the tip.
- A cup-shaped base to the flower.
Clue five: fruit
The fruit is either a dry capsule or a fleshy berry, containing many tiny seeds (seed dispersal in melastomes).
Look-alikes to avoid
Several other plants have curved, longitudinal veins and can be confused with melastomes:
- Dogwoods (Cornus): also show veins that curve towards the tip, but have different flowers and fruit.
- Plantains (Plantago): show parallel veins but have a rosette habit and tiny wind-pollinated flowers.
- Some Myrtales relatives: the order Myrtales includes many families with similar features, so check the flowers.
Exceptions within the family
Not every plant historically included in the family has the typical veins. Memecylon and its relatives have pinnate, feather-like venation, which is one reason some authorities treat them as a separate family (Memecylon). Some tiny herbs have leaf patterns that are hard to read.
Practical tips
- Start with the leaves, then confirm with the flower if one is present.
- Use a hand lens to examine anthers and hairs.
- Photograph the plant from several angles, including leaf undersides.
- If unsure, compare with herbarium images online (herbaria).
Takeaways
- Three or more strong longitudinal veins with ladder-like cross-veins are the best clue.
- Opposite leaves without stipules support the identification.
- Pore-opening anthers with curved appendages seal the deal.
- A few relatives and look-alikes are exceptions, so use more than one character.