Medicinal and aromatic plants – industrial profiles

Generic status and relationships
Lavandula
is a member of the Lamiaceae (Labiatae) family and belongs to the subfamily
Nepetoideae. Within the Nepetoideae a number of tribes are recognised and 
Lavandula
is 
currently treated as a distinct and isolated group of its own, that is, the tribe Lavanduleae (Endl.)
Boiss containing just the single genus 
Lavandula
(Cantino 
et al
., 1992).
What makes a lavender a lavender
The genus in terms of its general morphology is a rather mixed and divergent group. It is
defined by the nectary lobes being opposite the ovary’s rather than alternate (which is the case in
all other Lamiaceae). The combination of a compact terminal spikes of flowers usually borne on
a long peduncle (flower stalk); the declinate stamens (stamens curved downwards) borne within
the corolla tube and persistent bracts are characteristic.
Many species are highly aromatic due to the presence of essential oils that are borne in glands
covering much of the plant. In habit they vary from woody shrubs up to a metre in height, to
perennial woody-based shrubs or annual herbs. The leaves can be entirely or deeply dissected,
and are often absent in some of the Arabian species. The flowers (spike) consists of cymes, a
branching determinate inflorescence with a flower at the end of each branch, either an opposite
decussate arrangement (each pair of flower whorls at right angles to the pair above or below) or
an alternate spiral arrangement. The cymes are subtended by bracts, which vary in their size,
shape and nervation, which can be diagnostic for many species. The cymes can be single flowered
usually without bracteoles or many flowered (3–9 flowers per cyme) with bracteoles. The bracte-
oles are small, often minute, bracts borne at the points of branching within each flower whorl. In
some species, such as 
L. stoechas
and 
L. dentata
, the bracts at the apex are enlarged, coloured and
sterile and known as a coma. The calyx is (two-lipped) bilabiate and varies in the number of
nerves, lobe shape, presence of an appendage, colour and provides many important characters
used to diagnose both sections and species. The corolla is usually bilabiate, tubular and with five
lobes varying in size, colour, shape and markings.

---

4
Tim Upson