Broom, *Cytisus*: planting, pruning, maintenance

Description and Botany

The genus Cytisus, closely related to Genista, includes around 50 species of bushes mostly native to the Mediterranean region, the Middle East, and Africa. They can be found from high mountains, in arid and dry places, to low-altitude heathlands where they grow spontaneously. The Broom, sometimes mistakenly called cytisus (which is the common name for Laburnum), belongs to the large family of legumes (Fabaceae).

Among the most popular species is Cytisus scoparius, sometimes referred to as “Broom”, from which the most numerous varieties, cultivars (‘Boskoop Ruby’, ‘Lena’, ‘Andreanus’) and hybrids are derived. The Spanish Broom (Spartium junceum), often confused with rush, is spontaneous and very useful by the seaside: it can become invasive and is considered in the south as one of the garden pests, reseeding and rooting powerfully where it thrives.

Also found is the early broom (Cytisus x praecox), the Purple Broom (Chamaecytisus purpureus) with its purplish-pink flowering, or Cytisus battandieri, known as the Pineapple Broom, with very characteristic flowers shaped like and smelling of pineapple. Genista lydia is the least hardy of the genus. The Dyer’s Broom (Genista tinctoria), common broom, or bastard broom is known for its medicinal and dyeing properties.

Cytisus kewensis, Cytisus decumbens, Cytisus scoparius var prostratus, and Cytisus x racemosus Phebus, a superb improvement of the Tenerife broom, are creeping yellow brooms.

Cytisus scoparius – botanical illustration

Brooms are mainly classified according to their size; they are bushy or ground-covering. This small bush develops a more or less erect, highly branched habit, sometimes very dense, but with a light appearance. It grows in bushy clumps, reaching 4 m high and 2 m wide (but on average rarely more than 2 m) for bushy species. The brooms with a prostrate, creeping, and spreading habit like Genista lydia form dense small cushions of vegetation that are slightly spreading, not exceeding 20 to 70 cm in height for a span of about 1 m after many years.

The growth of the Broom is normal to fairly slow, and its lifespan is short, lasting 5 to 10 years at most.

With its numerous soft and spreading branches, sometimes slightly arched, its silhouette is both graceful and rustic. The long, slender, finely branched stems remain green all year round and become woody over time.

The numerous fine and channelled branches, with marked angles, bear small simple leaves or divided into three leaflets, alternate ovate to lanceolate measuring from 0.5 to 10 cm long. The leaves at the base of the stems are sessile while the leaves at the tips of the branches are petiolate. Deciduous, they often fall with the arrival of summer heat.

Ranging from fresh green to bright silky green, sometimes covered with a fine silky down, the foliage of the Broom contrasts beautifully with the flowering. In May-June, sometimes as early as March for the Cytisus and in summer for the Genista, the bush is then covered with a profusion of very bright flowers that almost entirely eclipse the foliage.

Flowers measuring 0.5 to 3 cm long appear abundantly, borne singly, in dense terminal clusters in Cytisus battandieri, or in often fragrant bouquets gathered along or at the tips of the branches. They are papilionaceous (butterfly-shaped) like pea flowers and consist of 4 petals, with the upper petal, which is also the largest, unfolding as a banner above the lateral petals or wings that close to form a keel.

Often a very bright golden yellow, transforming the bush into a spectacular ball of gold, they also come in purple or pale violet pink (‘Purple Broom’), ruby red (‘Boskoop Ruby’), yellow-orange (‘Goldfinch’), and are sometimes bicoloured tinged with orange or purple (‘Lena’, Cytisus scoparius ‘Andreanus’ golden yellow with purple wings), and more rarely white (Cytisus x praecox ‘Albus’, Cytisus kewensis).

They sometimes emit a sweet fragrance with honeyed notes or even overpowering in some brooms like Spartium junceum. The flowers of Cytisus battandieri or the Pineapple Broom smell of pineapple!

Several colours of brooms: Cytisus scoparius ‘Lena’, Cytisus procumbens ‘Zeelandia’, Cytisus ‘Boskoop Ruby’, Cytisus praecox ‘Albus’, Cytisus scoparius ‘Andreanus’.

The flowering lasts about 3 weeks before giving way to long flat black hairy pods measuring 2 to 3 cm long, which twist open when mature at the end of summer, expelling the seeds at a distance.

Easy to cultivate, this vigorous hardy shrub, most often down to -15 to -20°C, prefers to grow in full sun or light shade, in any light and well-drained soil, even poor and stony. It is an excellent plant for dry and rocky gardens or seaside in a large rockery, in a border, in a mixed hedge, or on a very sunny slope.

[caption id="attachment_47382" align="alignnone" width="1172"] Hairy pods, green then black at maturity.

In the past, the stripped branches of the broom were used for the making of coarse brooms. It also has many medicinal virtues, primarily diuretic.

Main species and varieties

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Cytisus praecox Allgold

An early flowering Broom, covered in abundant pure golden yellow flowers from March. Hardy down to -15, -20 °C.

• Flowering time April, May
• Height at maturity 1,20 m

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Cytisus scoparius Andreanus

A very floriferous and vigorous Broom covered in large golden yellow flowers with bright red wings. It develops an erect, fairly compact, yet light appearance.

• Flowering time June, July
• Height at maturity 2 m

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Cytisus scoparius Ruby

A compact, very floriferous Broom offering a profusion of ruby red flowers at the end of spring. Maintenance-free in borders, rockeries, or slopes.

• Flowering time June, July
• Height at maturity 1,50 m

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Cytisus x kewensis

A prostrate, fairly compact Broom perfect in the middle of a border of perennials. A profusion of creamy yellow and fragrant flowers.

• Flowering time June, July
• Height at maturity 50 cm

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Cytisus scoparius Cytisus Lena

A vigorous variety of Broom forming a spreading, compact bush ideal for borders and hedges. Its bright red and golden yellow flowering will create beautiful flowering scenes with no maintenance required.

• Flowering time June, July
• Height at maturity 1,30 m

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Chamaecytisus purpureus

A very attractive ground-covering bush, hardy, drought-tolerant, and easy to grow. Its small size also allows it to be grown in pots.

• Height at maturity 45 cm

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Cytisus decumbens

A ground-covering bush with a prostrate and spreading habit. With its bright yellow flowering, it will create an extremely bright floral carpet.

• Flowering time June, July
• Height at maturity 20 cm

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Cytisus scoparius Goldfinch

Its erect stems and yellow-orange and red flowering will bring a graphic effect to your garden. It has a lovely rounded habit.

• Flowering time June, July
• Height at maturity 1,50 m

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Cytisus battandieri

A curiosity with summer flowering in clusters of golden yellow flowers with a sweet pineapple scent! Its hardiness is average, tolerating -12 to -15 °C.

• Flowering time June to August
• Height at maturity 4 m

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Cytisus praecox Albus

An early compact Broom, very floriferous, offering a profusion of white flowers from March.

• Flowering time April, May
• Height at maturity 1,20 m

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Cytisus scoparius Luna

An excellent vigorous variety of Broom with an upright habit, not commonly found in our gardens despite its bright lemon yellow flowering. To be planted in a large rockery, a border, or on a sunny slope.

• Flowering time June, July
• Height at maturity 2 m

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Young plantation

Where to plant broom?

Most brooms have an excellent hardiness that allows them to withstand temperatures below -15°C to -20°C in well-drained soil, as winter moisture can harm their hardiness.

Resistant to diseases, frost, and drought, broom is easy to grow in almost all regions. Some species, such as Spanish broom, Spatium junceum, are well adapted to coastal areas. Others, like the dyeing broom, fear the intense droughts of Mediterranean summers. Genistas (Genista lydia) have lower hardiness, preferring mild to warm climates and fearing excessively harsh winters.

Broom should preferably be planted in full sun, even in scorching exposure where it flowers better, although it tolerates light shade. It will only refuse to flower in deep shade.

Not demanding regarding soil type, it grows in almost any situation. A poor, neutral or slightly acidic, light and well-drained soil, even stony, preferably sandy, is sufficient. Most even accept slightly calcareous soils. However, it fears winter moisture, heavy and suffocating soils. Plant it away from freezing drafts and waterlogged soils.

Choose its location carefully as this bush dislikes transplanting; its roots are quite sensitive and delicate. Broom is unobtrusive and adapts to all gardens, bringing a bright and original touch. The genus includes dwarf species for dry, sunny rockeries and larger species.

In any case, since broom tends to spread, provide it with about 1.5 m of space in all directions so it can develop comfortably. Shrubby species will look magnificent at the back of a flowerbed, against a sunny wall, in a hedge, or in a large flowering and fragrant rockery.

Ground-cover varieties not exceeding 70 cm in height will be perfect for covering a rocky slope, a low wall, a very sunny border, or even a container to flower and perfume the surroundings of the house with their sweet scents.

When to plant broom?

Planting brooms is preferably done in autumn, from September to November, to encourage rooting before winter and to have flowering the following spring.

How to plant brooms properly?

In hedges and flowerbeds, depending on the varieties, space the plants about 1.5 m apart. Broom appreciates well-drained soils where water will not stagnate in winter: in heavy, slightly clayey soil, lighten it with turf, pumice, clay balls, or potting soil. In overly calcareous soil, acidify with heather soil.

• Soak the root ball in a basin of water
• Loosen the soil well
• Dig a hole 2 to 3 times wider than the size of the pot
• Make a good drainage layer (pumice, gravel, clay balls) at the bottom of the hole
• Plant the shrub in the centre of the hole
• Backfill and compact the soil around the base of the plant
• Mulch the base with a plant mulch to keep its roots warm during winter
• Water abundantly at planting, then regularly during the first summer, but without allowing water to stagnate at the base of the plant

In pots

Choose compact-growing varieties of broom with moderate growth (Cytisus decumbens, ‘Plena’). The substrate must be very well-drained to avoid stagnant moisture at the roots. Repot every 2 to 3 years.

• At the bottom of a large container of at least 70 cm in diameter, spread a good layer of drainage (gravel or clay balls)
• Plant in a light, neutral or acidic substrate
• Mulch to keep the surface cool
• In summer, water well during flowering, once or twice a week, without drowning the plant

Broom flower under morning dew.

Maintenance, pruning of broom and care

Once established, the Broom requires little maintenance. Some species are more resilient than others: once well-rooted, Spanish Broom is almost indestructible!

It offers a good tolerance to drought and does not require abundant watering except during the first two summers when you should water once or twice a week. After that, only water in case of prolonged heatwaves. To keep the base cool during the warm season, you can refresh the plant mulch in spring, especially in the first few years following planting. Undemanding, in open ground, it does not require fertiliser.

Early, more delicate Brooms can be protected with a winter cover in case of severe frosts.

In pots, water once or twice a week during summer, allowing the substrate to dry completely between waterings. If necessary, repot in autumn every 2-3 years into a slightly larger pot.

Pruning the Broom

Pruning is useful to maintain a compact habit and prevent it from becoming bare with age. It is a shrub with a relatively short lifespan; it will last longer and flower more generously if pruned regularly. Prostrate species require very little pruning.

• Each year after flowering, carry out a refreshing pruning by cutting back the tips of the branches by 15 to 30 cm to prevent fruiting, which exhausts the shrub
• Retain the old lignified wood but remove dead shoots
• In March, large Brooms can be pruned back hard if necessary (for example, if they become deformed under the weight of the crown) to 40 cm from the ground using pruning shears

Diseases and potential pests

The Broom is a bush that shows good resistance to diseases with some precautions during its installation.

While most can tolerate lime, in overly shallow chalky soil, it may show signs of chlorosis, which causes yellowing of the leaves. The broom is particularly sensitive to excess moisture, which can harm its hardiness and cause its roots to rot. To prevent rot, ensure that the soil is sufficiently draining.

It may also be subject to the formation of galls caused by a parasitic mite (phytoptus) that sometimes attacks the tips of the branches. At the beginning of spring, spray repellent decoctions of horsetail. In case of infestation, remove and burn the affected branches.

Multiplication

If brooms are propagated by sowing in March or in autumn with harvested seeds, we recommend propagation by cuttings, the simplest and fastest method. It allows for the renewal of broom plants, which age quickly. The best time is when the plant is in full growth, which is summer for most regions.

By herbaceous cuttings

• In June, take non-flowering, green lateral shoots from the year that are 10 to 15 cm long by simply detaching them to obtain a heel
• Scrape the bark for a few centimetres and remove the lower leaves
• Keep two pairs of upper leaves
• Plant the cuttings in pots or trays in a light, well-draining mix of coarse sand and special cutting compost
• Keep the substrate just moist in partial shade until rooting, which takes 1 to 2 months
• Transplant the cuttings into pots in autumn
• Plant in the ground in spring and water well during the first year

It is also possible to take semi-woody cuttings later in the season, in late summer or early autumn.

→ Learn more with our tutorial: How to take a broom cutting?

Associate

Thanks to its medium dimensions and its dense, upright or spreading silhouette, yet always attractive and airy, the Broom can be used in multiple ways in all natural and wild gardens where it will be a lovely source of light. It will help create colourful and lively spring or summer scenes.

An example of pairing: Cytisus ‘Moonlight’, Azalea such as the variety ‘Palestrina’ for example, Lunaria annua ‘Variegata Alba’.

It will find its place within a flowering hedge, a large shrub bed, or a sunny rockery. It can serve as a focal point in the centre of a small garden or in a pot on a terrace.

Its branches, adorned with a profusion of small flowers most often golden yellow, will stand out powerfully in gold/blue compositions with the blue flowers of aconites and Caucasian forget-me-nots. Varieties with pink, white, or cream flowers pair well with all warm shades like peach or apricot from low-growing helianthemums, potentillas, or benoîtes.

Cytisus praecox can be associated with the late flowers of spring bulbs such as daffodils, tulips, wallflowers, fritillaries, and perennials like spurge.

In a hedge, the light branches of the Broom can be combined with many shrubs with remarkable foliage in purple or with staggered flowering: forsythia, Syringa, ceanothus, buddleias, euonymus, a smokebush, a Prunus. Its branches will stand out well against a backdrop of dwarf conifers.

It will enhance the beauty of a bed alongside a peony and shrubby sages, Erigeron karvinskianus, California poppies, and perennial geraniums for beautiful low-maintenance flowering scenes.

With their diffuse structure, the flowers of the broom highlight plants with more defined shapes like grasses or heathers.

A spring pairing idea: Cytisus praecox ‘Albus’, Brunnera macrophylla ‘Green Gold’, Daffodil ‘Paperwhite’, Daffodil ‘Tête à tête’, and Chionodoxa sardensis.

Pair it with sun-loving shrubs suited to dry, poor soils, such as cistus and strawberry trees with lovely red berries in autumn.

In a garden without irrigation, ground-cover broom varieties will occupy a large slope alongside other unpretentious ground covers like rosemaries or creeping ceanothus.