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 many others. It grows quickly in a lax, bushy habit. 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.
|Botanical Name||Cytisus spp. and Genista spp.|
|Common Names||Broom, Broom Plant, Sweet Broom|
|Plant Type||Evergreen shrub|
|Mature Size||6-8 ft. tall, 5-6 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||5-8 (USDA)|
|Toxicity||Toxic to cats, dogs, and humans|
Broom Plant Care
Broom plants can be used in a variety of areas in your landscape thanks to their varying heights and colorful displays. For example, brooms will display pops of color in the spring and summer which can contrast nicely when planted in front of other green shrubs. Or, use taller varieties of broom plants as a hedge or border. The dwarf varieties of brooms look beautifully nestled as mass plantings in a rock garden.
Broom plants like workable, well-draining soil that's prepared in an open, sunny locations. The plants will tolerate wind, poor soil, and even rocks. This wild shrub will thrive throughout drought and cold for years to come.
Broom plant's from the Cytisus species EW considered invasive, especially noted in northern California and Washington state.
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 with fewer blooms.
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.
Mulch alkaline soil in the spring with ericaceous compost.
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 an 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 2-inch 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, cats, and horses. Ingesting large quantities could impact the heart or central nervous system of a pet because of the toxic alkaloids they contain. The alkaloids, cytisine and sparteine, are closely related to nicotine.
Symptoms of Poisoning
Symptoms of cytisine poisoning include:
- Chest pain
- Potential death
Sparteine is a class 1a antiarrhythmic agent, acting as a sodium channel blocker and interfering with the natural rhythm of the heart. Symptoms of sparteine poisoning include:
- Abdominal discomfort
- Loss of appetite
Pregnant women should avoid consuming this plant because it may also induce contractions.
Broom Plant Varieties
Cytisus Plant Varieties
- Cytisus 'Ardoinii' grows a humble 5 inches tall. This dwarf, prostrate alpine shrub plentifully blooms in yellow every spring.
- Cytisus x kewensis reaches 2 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 4 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 5 feet tall offering pale yellow flowers in early May.
- Cytisus 'Burkwoodii' reaches between 5 and 7 feet tall. It has crimson flowers in late spring.
- Cytisus scoparius (common broom) puts on a long show of yellow flowers on its 5-foot 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 plant is also known as hedge broom. The dwarf variety reaches about 5 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 that can be trained as a small tree. Protect from severe winter conditions by growing it against a southeast- or west-facing wall. Give it lots of sunshine.
Genista Plant Varieties
- Genista lydia (Lydian broom) grows 2 feet tall and spreads 3 feet. Its green arching stems are covered with golden yellow flowers in May and June.
- Genista hispanica (Spanish gorse) reaches 3 feet tall and spreads at least 7 feet wide. Golden flowers cover this dense, spiny shrub in June and July.
- Genista aetnensis (Mount Etna broom) grows 10 feet tall and spreads 8 feet wide with linear leaves and yellow flowers that bloom in July.
This low-maintenance plant usually does well without pruning, but because many brooms have relatively short lives, pruning can extend their line span. There are slight differences in pruning Cytisus and Genistas.
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 a 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.
Propagating Broom Plant
Be certain to transplant cuttings in the spring when they reach a few inches tall because their root systems run deep and aren't always happy to be disturbed.
- Clip 3-inch cuttings below a leaf node that are especially ripe and healthy off of semi-mature wood in July or August; don't take cuttings any earlier or they may not root.
- Dip the bottom in rooting hormone.
- Place in flats filled with moist, well-draining potting compost.
- Keep moist while rooting the cuttings slowly in a cold frame.
- Plant in the spring, but don't wait too long as the roots will grow deep and the plant will resent the transplant.
How to Grow Broom Plant From Seed
Harvest and sow seeds when the pods turn black which means they're ripe. Note that germination may not happen with every fussy broom plant seed.
- Soak seeds in hot water for about 24 hours before sowing.
- Use pots or flats filled with sandy soil.
- 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.
- Plant in the spring, but don't wait too long because the roots will grow long and the plant does not do well when transplanted at a late stage.
Common Pests & Diseases
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. Broom plants are also susceptible to gall mites, an attack caused by fungus dieback; it will result in stunted growth, which is sometimes desired where the plant is considered invasive.