Cytisus scoparius aka Broom

Cytisus scoparius produces profuse, showy golden yellow flowers from May to June. The pea-like flowers are 20-30mm long and 15-20mm wide, covering the green stems in spring. The flowers are rich in nectar and pollen, attracting bees, butterflies, and other beneficial insects. After flowering, the plant develops seed pods that mature to black in late summer and burst open with an audible crack, forcibly scattering seeds.

Scotch broom can be propagated from seed or cuttings. For seeds, sow fresh seed in autumn in a cold frame for best results. Stored seed requires a 24-hour warm water soak followed by one month cold stratification, then germinates in 4 weeks at 20°C. Pot seedlings immediately as they quickly become intolerant of root disturbance. For vegetative propagation, take half-ripe cuttings (4-7cm with heel) in August, or mature wood cuttings in October/November.

Prune Cytisus scoparius using RHS pruning group 3 guidelines. Trim after flowering to maintain shape, but never cut into old wood as it does not regenerate well from mature stems. Light pruning of green growth helps maintain a compact form and encourages flowering.

Common pests include aphids (particularly Aphis cytisorum, which is resistant to the plant's defensive alkaloids) and spider mites. Diseases include powdery mildew and leaf spot, with signs such as yellowing leaves or white powdery patches. Root and basal stem rot caused by Phytophthora species has also been reported. Despite producing defensive alkaloids, the plant can be affected by specialized insects including broom twig miners and seed beetles.

There are over 50 cultivars of Cytisus scoparius, with popular varieties including 'Andreanus' (bicolor with dark orange-red and yellow flowers, growing to 8 feet), 'Moonlight' (creamy-white to primrose yellow flowers, 5-6 feet tall, very common in trade), and 'Goldfinch' (yellow and orangey-red flowers in May-June). Note that in some regions like Oregon, all Scotch broom varieties are prohibited due to invasive potential, regardless of cultivar.

Cytisus scoparius is hardy in USDA zones 5-8 and UK hardiness zone 5, tolerating temperatures down to approximately -20°C. Native to western and central Europe including Britain, it thrives in sandy pastures, heaths, and coastal areas. Plant in full sun with shelter from cold drying winds. It's ideal for poor, acidic soils and excels in gravel gardens and exposed or coastal locations due to excellent wind tolerance and maritime exposure resistance.

Cytisus scoparius does not require fertilizer and actually thrives in poor soils. As a legume, it has a symbiotic relationship with Rhizobium bacteria that fix atmospheric nitrogen in root nodules, making it self-sufficient for nitrogen. This nitrogen-fixing ability even benefits surrounding plants. The shrub performs best in nutrient-poor acidic soils, and fertilization is unnecessary and may even be detrimental to its growth.

Scotch broom is very cold-hardy, tolerating temperatures down to approximately -20°C. Hardy in USDA zones 5-8, it withstands harsh winters and is native to temperate European climates. While frost-tolerant, it benefits from shelter from cold drying winds. The plant is deciduous, naturally dropping leaves in autumn and going dormant through winter, emerging with new growth in April.

Cytisus scoparius is not particular about humidity and tolerates a wide range of atmospheric conditions. It grows successfully in both coastal areas with higher humidity and inland dry locations. The plant even tolerates atmospheric pollution and smoky atmospheres, demonstrating its adaptability to various environmental conditions. No special humidity considerations are needed for cultivation.

Cytisus scoparius is insect-pollinated, with flowers rich in nectar and pollen that attract bees, butterflies, and other beneficial insects. The bright yellow pea-like flowers are perfectly adapted for bee pollination. The plant serves as a food source for the green hairstreak butterfly larvae and provides important early-season nectar for pollinators. After successful pollination, it develops explosive seed pods that burst open to scatter seeds.

Cytisus scoparius has very limited edibility (rated 1 out of 5) and should be approached with extreme caution due to toxic alkaloids. Flower buds can be pickled and used as a caper substitute or added to salads. Roasted seeds have historically been used as a coffee substitute, and young green tops flavored beer. However, all parts contain toxic quinolizidine alkaloids, and consumption can be dangerous. Edible uses should only be attempted with expert knowledge.

Cytisus scoparius has a medicinal rating of 3 out of 5, with young herbaceous flowering shoot tips used as cardiotonic, diuretic, cathartic, and vasoconstrictor agents, primarily for heart complaints. However, PFAF and medical sources strongly warn that any treatment should only be under expert supervision. The plant contains variable amounts of toxic alkaloids (sparteine, cytisine) that can cause fatal poisoning. It's contraindicated in pregnancy and high blood pressure. Self-medication has resulted in deaths from heart failure and circulatory weakness.

Cytisus scoparius has extensive non-food uses (rated 4 out of 5). The bark yields excellent fiber (2-9mm length) for manufacturing paper, cloth, and nets. Branches are used for basketry, brushes, and traditional besoms (brooms). It produces yellow, brown, and green dyes from different plant parts, and flowers yield essential oils for perfumery. The hard, beautifully-veined wood is valued by cabinetmakers. It's effective for soil stabilization and erosion control as a sand binder, and the bark contains useful tannins.