Bright-yellow flowers are loved by some people but hated by others. I think they add a cheerful boost to any garden, especially when they are lovely flowers from the pea family, Fabaceae, like those provided by the brooms, or Genista.
Genista is a genus of hardy to half-hardy, largely deciduous but sometimes evergreen or semi-evergreen shrubs or trees. Their pea-like flowers are borne in spring or summer and usually clothe the plant for an excellent show and sometimes they are fragrant.
They are commonly known as brooms, alongside closely related genera Cytisus and Chamaecytisus, because some of their species have brush-like slender green stems and very small leaves that are adaptations to dry growing conditions. But not all of the species look like this. Some have branched stems, trifoliate leaves or spiny stems like close relative gorse, Ulex europaea.
They are not widely planted but perhaps the best known species is the Mount Etna broom, G. aetnensis Award of Garden Merit (AGM). It can become a large shrub or small tree up to 8m tall and has the classic slender broom stems and masses of fragrant, bright-yellow, pea-like flowers. There are also several lovely medium-sized shrubs with trifoliate leaves and fragrant flowers of varying degrees of hardiness from tender to half-hardy including G. × spachiana AGM, G. canariensis AGM and G. ‘Porlock’ AGM. There is also a version of gorse with spikey stems, G. hispanica from Spain.
For the rock garden there are several small or prostrate shrubs that look very effective spilling down the rock faces or across a gravel garden. These include the highly popular low-growing G. pilosa ‘Procumbens’ AGM, which is nearly always the form found in garden centres, and the dwarf shrub G. tinctoria ‘Royal Gold’ AGM.
Genista also has an interesting history. The UK native G. tinctoria has been used in the past as a yellow dye and combined with woad to create green. Extracts have also been used to help heal fractures, tumours and open wounds, and used to treat gout and rheumatism, though scientific research has not proven it safe to use. The name of the Plantagenet royal line is derived from this genus, being a corruption of planta genista.
It is an easy genus to cultivate because the plants cope in any soil type, including poor soils, though they need good drainage. They like a hot and sunny position in full sun. Because many of them are subject to fire in the wild, they regenerate from the roots even if the upper parts have been damaged.
What the specialists say
Peter Chapman, managing director, Perryhill Nurseries, East Sussex
"Genista are easy to grow, varying from the virtually prostrate G. sagittalis to G. cinerea and
G. aetnensis, which are large shrubs to about 3m tall. They will succeed in well-drained even dry soils in full sun. Acid, neutral and alkaline soils all seem to be fine.
"We do not stock a vast range but the most popular is G. aetnensis, which makes a large shrub to small tree and is often asked for as a specimen plant. G. lydia is tough and is a mass of flower in May and June. G. hispanica is prickly and flowers at about the same time. G. tinctoria has a longer flowering period, starting in June, often through to late summer. ‘Royal Gold’ is a good selection. They are a trouble-free group of plants and useful for dry sunny sites where little maintenance is needed."
Ben Wighton, assistant head gardener, Lincoln’s Inn, London
"Genista is not a widely grown genus but we have a large specimen tree of G. aetnensis. It makes for an unusual end to one of our borders, with its very long brush-like shoots. It adds a lot of texture, especially on a windy day. In summer it bursts into flower and adds a bright-yellow accent to the border, which no one expects.
"We don’t grow any others but I have seen the trifoliate forms with wonderfully fragrant flowers, maybe G. ‘Porlock’ or G. canariensis, grown in front gardens. They are both shrubs on the tender side but the ones I’ve seen are being grown against a wall so they are getting shelter from it. Each time I walk past them in the spring or summer I have to take a sniff of their gorgeous yellow flowers."
Species and varieties
G. aetnensis AGM (H5) is a large deciduous shrub or small tree with slender, arching green shoots and small, sparse leaves. Bright-yellow, fragrant, pea-like flowers produced in abundance in mid to late summer. Height and spread: 4-8m.
G. canariensis AGM (H1c) (syn. Cytisus canariensis), also known as the florists’ genista for its slender terminal racemes of fragrant yellow flowers produced in spring and summer. A vigorous evergreen shrub with a bushy, upright habit and small trifoliate leaves. Height 2.5-4m. Spread: 1-1.5m.
G. lydia AGM (H5) is a compact, deciduous dwarf shrub with arching or trailing branches. It has small leaves and bright-yellow pea-like flowers that are borne in terminal clusters in early summer. Height: 0.5m. Spread: 1m.
G. lydia Bangle = ‘Select’ is a low-mounding selection that produces masses of bright-yellow flowers in spring. This variety provides a well-branched plant with an interesting texture. Recommended for mass planting and for containers. Height and spread: 30-60cm.
G. hispanica is also known as the Spanish gorse because it has a similar spiny nature, but it is deciduous. It produces green stems and spines as well as leafy flowering shoots bearing terminal clusters of bright-yellow flowers in late spring and early summer. Height: 1m. Spread: 1.5m.
G. pilosa ‘Lemon Spreader’ is a low-growing spreading shrub that has lance-shaped leaves with long racemes of flowers. Hardy throughout most of the UK. May suffer foliage damage and stem dieback in harsh winters in cold gardens. Height: 30cm. Spread: 1m.
G. pilosa ‘Procumbens’ AGM is an excellent low-growing form that makes a compact, prostrate mound with masses of bright, golden, pea-like flowers throughout the summer. Good in rock gardens. Height: 10cm. Spread 30-60cm.
G. pilosa ‘Vancouver Gold’ AGM forms a carpet of grey/green stems with insignificant leaves. Masses of yellow pea-like flowers smother the plant in late spring. Excellent on slopes, in the rock garden or in tubs. Height: 20cm. Spread: 75cm.
G. ‘Porlock’ AGM (H3) is a semi-evergreen, medium-sized shrub with small leaves and racemes of fragrant, bright-yellow flowers in spring. Height and spread: 1.5-2.5m.
G. sagittalis is a mat-forming type with prostrate stems but erect flowering shoots topped with bright-yellow flowers. Height: 10-25cm.
G. × spachiana AGM (H1c) (syn. Cytisus × spachianus) is an evergreen shrub with small dark-green trifoliate leaves and very fragrant small yellow flowers in slender terminal racemes, in late winter and early spring. Tender, so it may need the shelter of a conservatory or greenhouse, but can be tried outside where mild and sheltered. Height and spread: 3m.
G. tinctoria is a variable deciduous shrub with small lanceolate leaves and yellow pea-like flowers borne in erect narrow racemes from spring to early summer. Height: 60-90cm. Spread: 1m.
G. tinctoria ‘Royal Gold’ AGM (H6) is a deciduous dwarf shrub of upright growth with small, narrow, dark-green leaves and deep golden-yellow flowers in spring and early summer. Height and spread: 0.5-1m.
Thank you to Floramedia, which supplied the images for this article from its photo library