Genista tinctoria aka Dyer's Greenweed

Genista tinctoria is a deciduous shrub in the pea family. Its common names include dyer's broom and dyer's greenweed. It grows wild from Europe to western Siberia and Afghanistan. It is native to Britain and Ireland. Wild plants grow in meadows, pastures, heaths, and field edges. They often grow on poor soil. The shrub grows slowly and spreads from several stems. Garden plants reach 2–3 feet [0.6–0.91 metres] tall and wide. RHS gives an upper size of about 3.3 feet [1 metre].

The green stems are thin, upright, and sparsely branched. A few hairs cover their surface. Small green leaves grow in an alternate pattern. Each leaf is simple and joins the stem without a stalk. The leaves range from oval to narrow and pointed. Hairs occur on the upper face and along the edges. Yellow, pea-shaped flowers form upright racemes at the stem tips. Each bloom measures less than an inch across. Main flowering falls in June and July. RHS reports flowers from midsummer into early autumn. Bean-like pods follow the flowers. These turn brown from August to October.

Grow this shrub in full sun with good soil drainage. It suits sandy, stony, or gravelly ground with few nutrients. RHS also lists loam and chalk as suitable soils. It accepts acid, neutral, and alkaline conditions. Soil moisture can range from dry to moderately moist. Established plants withstand drought. The species grows in USDA zones 4–7 and has RHS rating H6. Choose its site with care, since it dislikes transplanting. Cut back after flowering to help extend the bloom season. Avoid cuts into old wood. Raise new plants from seed or summer semi-ripe cuttings.

Dyer's broom suits borders, rock gardens, banks, and ground cover. Its green stems also offer winter interest. The plant fixes nitrogen and tolerates poor ground. People have used it to make yellow fabric dye. Mixing that dye with woad gives green shades. Stem fibre has served for rough cloth and cord. Sources also record its use in herbal medicine. Plants For A Future lists leaves as edible. It records pickled flower buds as a caper substitute. It also mentions seeds as a possible coffee substitute. That source reports no known hazards, but does not establish safety.

Serious pest and disease trouble is not usual. Aphids and gall mites may occur. Possible diseases include blight, dieback, powdery mildew, and rust. Honey fungus may affect plants where it already occurs. RHS notes that the degree of risk remains unclear. The shrub has escaped gardens in parts of North America. Some populations have become invasive, including in eastern coastal areas. Watch for spread beyond the planting site.