Most field weeds are content to compete with cultivated crops in terms of living space. Not so with Red Bartsia, which is semi-parasitic and lives on the roots of other plants, in particular grain.

On its roots are suction discs and the root-like outgrowths (haustoria) by which it attaches itself to the roots of neighbouring plants and through which it absorbs food from its host. In all other respects, however, it is no different from other non-parasitic plants.

The Dandelion is also a classic example of photonasty: the flower- heads open in full sun and close in the evening. Also, its flower-stems demonstrate the phenomenon of tissue tension: if the stalk is cut in two lengthwise, each half curls in a spiral below the flower.

At the seedling stage, however, it is not independent: if young Red Bartsia roots do not find the roots of a host plant to which they can become attached they soon perish. It is for this reason that Red Bartsia is such an aggressive weed, its progeny – when present in quantity – sometimes reducing crop yields by as much as 50 per cent.

However, the resulting offspring exhibit extreme morphological variability. Typical of this variation in form are the leaves of the Dandelion. T. officinale is also a medicinal plant.

Only rarely are the three species found growing together in equal numbers; usually one of the three predominates. The flowering period is from May until July, sometimes continuing until August.