This is an invasive weed which is poisonous to livestock, often found growing in large clumps. Each stem has many (25–100) bright yellow, 5-petaled flowers, which may have a row of tiny black dots along the petal margins. The leaves provide an important diagnostic feature; they appear to be perforated, the result of the presence of many small, clear oil glands. Garden varieties with larger blossoms sometimes escape and naturalize. At first sight the leaves bear a resemblance to French Broom (Genista monspessulana), but the plants are unrelated. Like other Hypericum species, this is sometimes called St. John’s Wort, and has uses in traditional medicine.