[12] In late summer, its legumes (seed pods) mature black, 2–3 cm (3⁄4–1+1⁄4 in) long, 8 mm (3⁄8 in) broad and 2–3 mm thick; they burst open, often with an audible crack, forcibly throwing seed from the parent plant.

This species is adapted to Mediterranean and coastal climates, and its range is limited by cold winter temperatures.

The seeds, seedlings, and young shoots are sensitive to frost; adult plants are hardier, and branches affected by freezing temperatures regenerate quickly.

The characteristic constituents are biogenic amines (mostly tyramine in the young shoots), flavonoids (spiraeoside and scoparoside), isoflavones and their glycosides (genistin), as well as allelopathic quinolizidine alkaloids (mostly sparteine, lupanine, scoparin and hydroxy-derivatives), which defend the plant against insect infestation and herbivores (with the exception of the resistant aphid species Aphis cytisorum).

[3] Outside of its native range, it is an ecologically destructive colonizing invasive species in grassland, shrub and woodland, and other habitats.

[19][20] Cytisus scoparius has been introduced into several other countries and continents, outside of its native range, and is commonly classified as a noxious invasive species in western North America, mainly in British Columbia (including on Vancouver Island), California, Oregon, Washington (west of the Cascades), the Sierra Nevada range,[21] fragmented areas of North America's eastern seaboard,[19] as well as Australia (where it is a declared weed),[22][23] New Zealand,[24] and in India.

[26] It is estimated that broom is responsible for US$47 million in lost timber production each year in the state of Oregon.

[37] Oxysparteine, produced from the action of acid on the sparteine, is useful as a cardiac stimulant and has the advantage over digoxin that it does not accumulate in the body.

[38] In Welsh mythology, Blodeuwedd is the name of a woman made from the flowers of broom, meadowsweet (Filipendula ulmaria) and the oak by Math fab Mathonwy and Gwydion to be the wife of Lleu Llaw Gyffes.

[39] However a traditional rhyme from Sussex warns: "Sweep the house with blossomed broom in May/sweep the head of the household away.

[37] The name of the House of Plantagenet, rulers of England in the Middle Ages, may have been derived from common broom, which was then known as planta genista in Latin.

[41]: 9 [42]: 1  The plant was used as a heraldic badge by Geoffrey V of Anjou and five Plantagenet kings of England as a royal emblem.