|Teasel - a semi-carnivorous plant
Above: Wild Teasel, Dipsacus fullonum, Teasel family (Dipsacaceae).
The teasel (Teazel, Dipsacus) is a striking grassland dicotyledonous plant and flower. The
club-shaped plant, up to about 1 to 2.5 m tall, is immediately recognisable by its large spiny and
club-like flower head, which 4-10 cm long. Recall that an inflorescence (main flowering shoot)
may bear one or more flowers, many in this case, and that each flower is born on its own stalk,
axis or shoot called a peduncle. In the photo above you can see the inflorescence - its is the
single terminal shoot bearing the flowers that emerges above the final whorl of green leaves
(which we can call bracts). This is a monopodial inflorescence (bearing a single main axis) and
so is called a raceme (a cyme is a branched inflorescence). The inflorescence is also terminal,
growing at the end of a vegetative shoot. This single axis bears side-branches which are the
individual flower stalks which are so compressed and shortened in this case as to be unnoticeable
(we can say that the flowers are stalkless if there is no shoot length between the inflorescence
and the first whorl of flower parts) but the flower stalk continues as the main axis or peduncle
bearing the various parts of the flower.
The peduncle is typically compressed and very short, so that the whorls of modified leaves
(petals, sepals, anthers, carpels, bracteoles) occur close together, forming the flower. The
inflorescence bears a terminal cluster of flowers, the bracts of which bear spines. (Some of the
bracts form a cup or involucre around each flower). The four petals are fused into a four-lobed
corolla enclosing four stamens and one carpel. Each flower forms a fruit, whose wall develops
from the calyx tube - each flower has an epicalyx which persists and assists fruit dispersal by
means of the crown of spines.
Epicalyx and calyx: the calyx is a whorl of sepals which surrounds or occurs beneath the whorl
of petals in a flower and in some flowers another whorl of leaf-like structures occurs just beneath
or outside the calyx - this is the epicalyx. It consists either of bracteoles or sepal stipules.
Bracts and bracteoles: bracts are additional leaf-like structures borne either on the flower stalk
(which is very short and compacted in this case) in which case they are typically small and called
bracteoles, or at the base of the flower stalk (bracts). Both types occur in the teasel, and both
bear spines. The bracteoles often, as in the teasel, form a cup or involucre.
Stipules: leaves, and sepals (modified leaves) sometimes contain stipules (typically two per leaf
in a monocotyledon, and usually absent or 1-2 per leaf in a monocotyledon). They occur at the
leaf base, on the leaf stalk or at the base of the leaf stalk. They serve to protect developing
structures in the bud, such as a second leaf that is still developing. They may be so enlarged as
to appear superficially like another pair of leaves.
The single seed inside contains endosperm enclosing the embryo.
Above: the lavendar-coloured flowers open first in an equatorial belt around the middle of the
flower-head. Flowering then proceeds to both ends, forming two belts of open flowers moving
towards the ends (see the first photograph above) as the older flowers turn to seed. Notice the
whorls of long pointed leaves further down the vegetative shoot.
Visit www.microscopy-uk.org for a beautiful article on the Teasel, including close-up views of
Below: the dried flower-head persists as the seeds develop, into the Autumn (Fall) until the
These dry fruit-heads (borne on what
is now the infructescence rather than
the inflorescence). The spines are
quite capable of piercing human skin
and these heads were once used
extensively for teasing out fibres in the
processing of fabrics like wool. They
were also used to 'raise the nap' or lift
the fibres to make the fabric 'woolly'.
The Teasel is Semi-Carnivorous!
Another distinctive feature of the Teasel is the whorls of long vegetative leaves borne at intervals
along the main shoot. Each leaf is up to 20 to 40 cm long, bears spines along the underside of its
midrib, and is tapered (lanceolate). The leaves are not borne on stalks, but instead the leaves of
each whorl fuse into a cup-like structure around the stem, which can trap considerable quantities
of rainwater, which the plant may later utilise, but which also traps many insects which
decompose in the water. Experiments have shown that nutrients from the decomposing insects
are absorbed by the plant, increasing the number of seeds that are produced. Thus the Teasel is
partially carnivorous (insects are not apparently essential, but are a utilised source of nitrogen).
See also carnivorous plants.
Knautia arvensis (Field scabious) is also a member of the Teasel
Field Scabious. The fruit of scabious makes the relationship of
scabious to Teasel much more obvious.
Small Scabious (Scabiosa columbaria) is another member of the
teasel family. These pictures of Small and Field Scabious were
from the same sight (chalk grassland) where both types were
seen growing together. Small Scabious has corollas with 5 lobes,
whereas the corolla of Field Scabious is 4-lobed. Field Scabious
also has more coarse hairs, whilst in Small Scabious the size
difference between the outer florets and the inner florets is more
13 Dec 2015
6 Aug 2016