Today's “Plant of the Day” is Rhinanthus alectorolophus Scop. Pollich. from the Orobanchaceae family (or Scrophulariaceae family in older literature). In English, the plant is known as “Greater Yellow Rattle”. In German, the plant is called “Zottiger Klappertopf”
R. alectorolophus - habitus
Greater Yellow Rattle is a annual plant, which can reach heights between 10 and 50 centimeters (4.0 to 19.3 inches) The whole stalk is covered with many, small hairs, what is also the reason for the German name (“Zottig” means “hairy”). The leaves are arranged in a decussate leaf-pattern. They are linear to laceolate and have a roughly serrated margin. Their colour is a bright-green and they are also covered with many, smooth hairs.A petiole is missing or very short.
R. alectorolophus -stalk with hairs
The inflorescences are simple terminal racemes with distinctive, cygomorphic flowers. The calyx consists of four, green sepals, which are rhomboid. Like stalk and leaves, they are covered with hairs. These sepals are mostly grown together but they separate at the blade tip to four corners.
R. alectorolophus - inflorescence
From the calyx, the corolla blossoms. Each flower consists of four, yellow petals, which are grown together to an upper lip (which consists of a single petal) and a lower lip, which consists of three petals. As a result, the lower lip has three tips and the upper lip just one. However, the single petal of the upper lip is much larger than the whole lower lip. It's helm-shaped and slightly bend upwards.
R. alectorolophus - flowers
There are also two, blue extensions at the top of the upper lip (length: 1 to 2 millimeters) , which look like the teeth of a snake. As a result, the whole flower looks like the maw of a snake. The function of the extensions may be to guide pollinators like bumblebees to the nectar. Flowering time is between May and September.
R. alectorolophus - flowers; here, you can see the
blue extensions of the upper lip and the hairy calyx
with its four corners
The ripe fruits are capsules, which remain in the calyx. As a result, the species rattles if you shake them. This is an interesting feature of the whole Genus Rhinanthus and also responsible for the names “rattle” and “Klapptertopf” (German for “rattling pot”)
2) Habitat and Distribution
R. alectorolophus is native to Middle-Europe and can be found in Germany, Switzerland and Austria. It grows on nutrient-rich meadows and pastures (sometimes acres). The species prefers warm, bright places and a calcareous soil. It's not a rare species overall, but it misses in the Northern regions of Europe.
R. alectorolophus - leaf
Please note: the species is highly variable and there are many variants of R. alectorolophus, which differ in some minor features (e. g. longer internodes between the flowers). However, these aren't real subspecies; just expressions, which may vary from areal to areal.