Broom plants are small to medium-sized shrubs with evergreen or deciduous foliage. Leaves are green and small, usually lanceolate. The two main species that share the common name Broom are Cytisus and Genista. Both look very similar. The main difference is Genistas are more tolerant of lime in water and soil. From the Fabaceae (legume) or Leguminosae (pea) family, broom plants bear pea-like flowers in shades of yellow as well as cream, rose, crimson, orange, mauve, lavender, and brownish-red. It grows quickly in a lax, bushy habit generally six to eight feet tall and five to six feet wide depending on the variety.
Native to the Mediterranean, western Europe and North Africa, this bushy shrub is hardy in USDA Zones 5-8. One quite common sweet broom (Cytisus racemosus syn. Genista racemosa) is often found along highways on the west coast of the United States.
Some gardeners regard the broom plant to be an invasive weed, while others favor this attractive fast-spreading plant for its airy feel and scented summer blossoms, which attract many pollinators. Invite this shrub to add a wildness to your residential garden landscape, and it will thrive throughout drought and cold for years to come.
Position brooms in front of other green shrubs so that their spring/summer color pops in contrast. Group tall varieties as a hedge or border. Nestle mass plantings of dwarf varieties in a rock garden.
|Botanical Name||Cytisus spp. and Genista spp.|
|Common Names||Broom, Broom Plant, Sweet Broom, Scotch Broom|
|Plant Type||Evergreen shrub|
|Mature Size||6 to 8 ft. tall, 5 to 6 ft. wide|
|Soil Type||Well-drained, Loam, Poor|
|Soil pH||Acidic, Neutral, Alkaline|
|Bloom Time||Late Spring, Summer|
|Flower Color||Yellow, Cream, Crimson, Brown-Red, Orange, Rose, Mauve, Lavender|
|Hardiness Zones||5, 6, 7, 8 (USDA)|
|Toxicity||Toxic to pets|
Broom Plant Care
Prepare the soil so that it is easily workable and free draining. Select a bed in an open sunny location, as these plants will tolerate wind, poor soil, and even rocks.
Brooms grow best in an open area with full sun, though they will tolerate some shade. Follow the light and location directions for the specific variety. Overall, too much shade tends to make broom plants leggy and less plentiful in bloom.
Establish in well-drained loam or poor soil (clay, sand, or loam). Acidic soil is best. Cytisus dislikes alkaline/chalky soils and Genista tolerates lime more easily. Sweet broom can thrive in poor soil, through drought and neglect, and can even fix the nitrogen in the soil with fibrous, fast-growing stabilizing roots.
If the soil is alkaline, mulch with ericaceous compost in spring.
Water regularly for the first few months if there is not enough rainfall to keep the soil moist. Maintain moisture in its first year to establish roots. Give one inch of water each week during its first summer and during heat or drought. Let the soil dry out between waterings.
Sweet broom benefits from habitual watering if the location is dry and the soil is poor.
Temperature and Humidity
Sweet broom performs best in conditions that would cause many other flowering shrubs to fail. It will bloom as early as late winter and through the early spring months in the cool temperatures of USDA Zones 8-10. Temperatures between 35 and 60 degrees Fahrenheit during the autumn and winter months encourage blooming.
Apply a two-inch-thick layer of lightweight shredded bark mulch to keep the roots cool and the soil moist. This will also provide a layer of insulation against the hot summer sun. Make sure the mulch doesn't touch the base.
Is Broom Plant Toxic?
These plants can be problematic to pets such as dogs and horses, although they are not considered strongly toxic. However, ingesting large quantities could impact on the heart or central nervous system of a pet because of the toxic alkaloids they contain.
Symptoms of Poisoning
The alkaloids, cytisine and sparteine, are closely related to nicotine. If a high amount of cytisine is absorbed into the system, symptoms may include vomiting, convulsions, chest pain, and even death.
Sparteine is a 1a antiarrhythmic, acting as a sodium channel blocker and interfering with the natural rhythm of the heart. Other symptoms may include abdominal discomfort, diarrhea, incoordination, lethargy, loss of appetite, nausea, numbness and weakness. Pregnant individuals should avoid consuming this plant because it may also induce contractions.
Cytisus Plant Varieties
- Cytisus 'Ardoinii' grows a humble five inches tall. This dwarf, prostrate alpine shrub plentifully blooms in yellow every spring.
- Cytisus x kewensis reaches two feet tall and is ideal for rock gardens. This wide, low-growing shrub displays pale yellow to creamy white flowers in spring.
- Cytisus ‘Lena’ is another dwarf variety and grows four feet tall. Foliage is deep green and flowers are ruby red and yellow through spring and early summer. This compact variety is sometimes sold as C. 'Volcano.'
- Cytisus x praecox (Warminster Broom) grows to five feet tall offering pale yellow flowers in early May.
- Cytisus 'Burkwoodii' reaches between five and seven feet tall. It has crimson flowers in late spring.
- Cytisus scoparius (common broom or Scotch broom) puts on a long show of yellow flowers on its five-foot-tall reach from May to June. Modern hybrids offer a wide range of colors. 'Andreanus' has deep brown red and yellow flowers. 'Cornish Cream' has ivory cream and yellow flowers. 'Goldfinch' is crimson and yellow with pink and yellow wings. 'Killiney Red' is a smaller, compact variety with red blooms.
- Cytisus racemosus nana (dwarf yellow broom) has so many yellow flowers from spring to summer they nearly cover the whole plant. Good for creating a hedge in dry conditions, this 10-foot-tall plant is also known as hedge broom. The dwarf variety reaches about five feet tall and also grows well in containers.
- Cytisus 'Battandieri' grows 15 feet tall. Also known as pineapple broom or Moroccan broom, its bright yellow flowers produce a distinct pineapple scent from May to June. It is not particularly broom-shaped, formed more like a medium woody shrub which can be trained as a small tree. Protect from severe winter conditions by growing it against a south-east or west-facing wall. Give it lots of sunshine.
Genista Plant Varieties
- Genista lydia (Lydian broom) grows two feet tall and spreads three feet. Its green arching stems are covered with golden yellow flowers in May and June.
- Genista hispanica (Spanish gorse) reaches three feet tall and spreads at least seven feet wide. Golden flowers cover this dense, spiny shrub in June and July.
- Genista aetnensis (Mount Etna broom) grows 10 feet tall and spreads eight feet wide with linear leaves and yellow flowers that bloom in July.
Broom Plant Propagation
Soak seeds before sowing and germinate at 65 degrees Fahrenheit (indoors in March or outdoors in April depending on the climate). Cover early seeds or seedlings with a fabric or cold frame. Clip three-inch-long cuttings that are especially ripe and healthy in summer. Root them slowly in a cold frame.
This low-maintenance plant usually does well without pruning, but because many brooms have relatively short lives, pruning can extend their line span. Prune Cytisus varieties every year after they have stopped flowering.
When pruning Sweet broom (Cytisus racemosus), timing is of the essence. Flowers come on old wood and pruning at the wrong time could prevent or delay blooming. Prune in late spring or summer after bloom season is over. Do not prune in autumn or winter. Give the plant enough time to produce mature wood so that it will flower in spring again. Use very sharp, sterilized pruning shears to cut the plant back by one-third. Cut each time at a 45-degree angle. Cutting straight across will cause the stem to hold rainwater and rot.
Consider Pineapple Broom (Cytisus battandieri) as more of a woody shrub by removing any dead or damaged shoots after it stops flowering.
Pruning of Genistas can be more complicated. For example, Genista aetnensis can be cut back quite a few times each season to encourage bushy growth. Genista hispanica can be lightly sheared after it is finished flowering. Genista lydia does not need to be pruned at all.
Webworms are the most common issue to look out for. They tend to overwinter in old debris so rake the area around the plant completely clean. Sometimes broom plants are also susceptible to gall-mites, an attack caused by fungus dieback. The main sign of this would be black spots on the leaves and stems.