Here is some more information on Rue.

Rue, a hardy, evergreen, somewhat shrubby plant, is a native of Southern Europe. The stem is woody in the lower part, the leaves are alternate, bluish-green, bi- or tripinnate, emit a powerful, disagreeable odour and have an exceedingly bitter, acrid and nauseous taste. The greenish-yellow flowers are in terminal panicles, blossoming from June to September. In England Rue is one of our oldest garden plants, cultivated for its use medicinally, having, together with other herbs, been introduced by the Romans, but it is not found in a wild state except rarely on the hills of Lancashire and Yorkshire. This wild form is even more vehement in smell than the garden Rue. The whole plant has a disagreeable and powerful odour. The first flower that opens has usually ten stamens, the others eight only.

A bit of folklore that's always stuck in my head is the notion that foxes rubbed rue on their paws, so the hens wouldn't smell them coming.

(Ignoring the fact that I don't think chickens can smell, I've always had a mental image of a Beatrix Potter style fox pausing outside a henhouse and patting all his jacket pockets, thinking: "Now, where did I put that rue?")