Scotch broom (Cytisus scoparius) is a perennial shrub that commonly grows in Europe. Scotch broom is also referred to as the “common broom.” The plants grow in sunny areas in dry soil and can withstand acidic soil conditions. In Italian folklore, a scotch broom was burned to stop witches. Scotch broom was a historical symbol of French king Charles VI.
I. Appearance and Characteristics
Cytisus scoparius (syn. Sarothamnus scoparius), the common broom or Scotch broom, is a deciduous leguminous shrub native to western and central Europe. In Britain and Ireland, the standard name is broom; this name is also used for other members of the Genisteae tribe, such as French broom or Spanish broom; and the term common broom is sometimes used for clarification. In other English-speaking countries, the most common name is “Scotch broom” (or Scots broom); however, it is known as English broom in Australia.
Plants of C. scoparius typically grow to 1–3 metres (3+1⁄2–10 feet) tall, rarely to 4 m (13 ft), with main stems up to 5 centimetres (2 inches) thick, rarely 10 cm (4 in). Stems are ridged and green. The shrubs have green shoots with small deciduous trifoliate leaves 5–15 millimetres (1⁄4–5⁄8 in) long, and in spring and summer are covered in profuse golden yellow flowers 20–30 mm (3⁄4–1+1⁄8 in) from top to bottom and 15–20 mm wide.
Flowering occurs after 50–80 growing degree days. The seed pods have long hairs only along their seams. In late summer, its legumes (seed pods) mature black, 2–3 cm (3⁄4–1+1⁄4 in) long, 8 mm (3⁄8 in) broad and 2–3 mm thick; they burst open, often with an audible crack, forcibly throwing seed from the parent plant. This species is adapted to Mediterranean and coastal climates, and its range is limited by cold winter temperatures. It also adapts to windy oceanic climates. The seeds, seedlings, and young shoots are sensitive to frost; adult plants are hardier, and branches affected by freezing temperatures regenerate quickly. C. scoparius contains toxic alkaloids that depress the heart and nervous system.
A legume, this shrub can fix nitrogen in the soil through a symbiotic relationship with Rhizobium bacteria.
Phytochemicals
One of the main alkaloids of this plant is cytisine. The characteristic constituents are biogenic amines (mostly tyramine in the young shoots), flavonoids (spiraeoside and scoparoside), isoflavones and their glycosides (genistin), as well as allelopathic quinolizidine alkaloids (mostly sparteine, lupanine, scoparin and hydroxy-derivatives), which defend the plant against insect infestation and herbivores (with the exception of the resistant aphid species Aphis cytisorum).
II. How to Grow and Care
Sunlight and Soil
Scotch Broom loves a sunny spot. Find a location in your garden that receives at least six hours or more of direct sunlight daily for well-balanced growth and plenty of blooms. The soil should be well draining with a slightly acidic pH. Scotchbroom thrives in lean, low-fertility soils, just as long as the soil does not retain water. Scotch Broom is tolerant of salt and drought once it’s established, so it’s a great choice for planting near salt-treated walkways or in coastal areas.
Watering
Scotch broom can be damaged if it grows in waterlogged soils, so it should never be overwatered. When it is newly planted, it should be watered often enough to ensure that the soil is always moist. After this, the plant should be able to derive all of its water requirements from rainfall, except in times of drought. The soil should be allowed to dry out completely before any supplemental watering.
Fertilizing
Scotch broom does not require an excessive amount of nutrients. If it is grown in rich soil, it may not need any artificial fertilization. In poor soils, it is helpful to feed the plant with a balanced N-P-K fertilizer. This can be applied in the granular form once a season in spring or once a week from spring to fall in liquid form.
Pruning
It is also important to begin trimming when the tree is young. Begin your scotch broom pruning before the tree is mature, and prune back its stems annually. This stimulates growth to prevent that scraggly look. When you prune a scotch broom plant, be conservative about how much to trim. Only trim back a little to shape the tree. Never cut off more than one-quarter of the foliage in any one year. If you need to do more scotch broom pruning than this, spread the clipping over a number of years.
Once the tree has grown large, it is too late to repair its scraggly look. According to experts, the mature branches do not retain many green buds. If you cut these branches back severely, you are not likely to get a fuller plant; in fact, if you prune a scotch broom shrub in this manner, you may kill it.
Caring for Scotch Broom in Pots
Scotch Broom readily grows in containers; its lovely, upright, vessel shape makes a striking display in a container large enough to accommodate its mature height and width. Depending on the variety, Scotch Broom can reach over 4-6 ft wide and tall. Yearly pruning may be required to keep it manageable when planted in a container. Plant in average soil in a container that has plenty of drainage holes. Scotch Broom does not enjoy sitting in soggy soil, so be sure the soil is fast draining. Place the container in a full sun location; sunlight is key in developing more flowers, as optimal flowering requires at least 6 hours or more of direct sunlight.
Overwintering
Scotch Broom is winter hardy down to Zone 5 and generally doesn’t require extra winter care. If you live in a particularly harsh climate, you can put a few inches of natural mulch around the base of the root system for added winter protection.
III. Uses and Benefits
- Ornamental uses
Although in many areas it is considered invasive, scotch broom has some valuable uses in the garden. Where hardy, it can provide some winter foliage and color. Additionally, it is known for being useful on slopes or in poor, loose soil for erosion control. With similar uses, Heather, Shrub rose, and Ceanothus make good companion plants.
- Medicinal uses
Broom contains scoparin, which is a diuretic. The plant also is used as a cathartic and as a cardiac stimulant, which is credited to the presence of sparteine. A decoction or infusion of broom can be used to treat dropsy due to its diuretic action. An ointment can be made from the flowers to treat gout. Oxysparteine, produced from the action of acid on the sparteine, is useful as a cardiac stimulant and has the advantage over digoxin that it does not accumulate in the body.
- Culture uses
In Welsh mythology, Blodeuwedd is the name of a woman made from the flowers of broom, meadowsweet (Filipendula ulmaria) and the oak by Math fab Mathonwy and Gwydion to be the wife of Lleu Llaw Gyffes. Her story is part of the Fourth Branch of the Mabinogi, the tale of Math son of Mathonwy.
Broom was considered a sign of plenty when it bore many flowers. However a traditional rhyme from Sussex warns: “Sweep the house with blossomed broom in May/sweep the head of the household away.” Broom was also used in a decorated bundle of broom at weddings in place of rosemary when that was scarce, and its strong smell was said to be able to tame wild horses and dogs.
In Italy, the shrub was burnt with the intent of stopping witches.
