Easily mistaken for : many other St' John's Worts.

Easily mis-identified as : Pale St. John's Wort but that has downy rather than hairy stems, the leaves lack transparent dots and have black dots on the underside (only). Pale St. John's Wort lacks black dots on the petals, but has similar black dots on the sepals.

Some similarities to : Yellow Loosestrife and Goldenrod, both of these have spikes of yellow five-petalled flowers.

Slight resemblance to : Agrimony in that the flowers are yellow with five petals, but the flowers on Agrimony are held very close to the main stem.

According to some books and to Clive Stace, Hairy St. John's Wort has black dots on the extremities of the petals, but your Author can find no photographs on the web purporting to be both Hairy St. John's Wort and sporting black dots on the petals... Perhaps they are extremely small?

St John's Worts can cause photosensitivity in livestock which consume the plant, the toxins being cumulative and may go un-noticed at first, only appearing after the animal has consumed some for a few days. Light-skinned animals are more susceptible, and may develop dermatitis and blisters on non-pigmented parts of the skin such as mouth, nose and ears when exposed to the sun.

The stems yield a brown-red dye when alum is used as the mordant. The flowers, on the other hand, yield a yellow dye when alum is used as the mordant and an orange-red dye when tin is used instead.

All St. John's Wort plants contain Hypericin and Hyperforin as the main constituents, which together are thought to be responsible for its reported therapeutic effects which may be good for certain people (and bad for others). See Slender St. John's Wort for details of these and other compounds present in the Genus.