Cytisus scoparius Seeds | Common Broom

Common Broom (Cytisus scoparius) seed — Common Broom (*Cytisus scoparius*): native to Western and central Europe, from Ireland and Britain through France, the Low Countries and Germany to Poland and the western Mediterranean.

LATIN NAME: Cytisus scoparius

COMMON NAME: Common Broom

Plant Profile

Broom roots carry nodules formed with soil bacteria of the genus Bradyrhizobium. Inside the nodule the bacterium reduces atmospheric nitrogen to ammonia and hands it to the plant, which pays in sugars. That is why broom thrives on sand, gravel and mine spoil where nitrogen is scarce, and why it can change the soil it invades, leaving a nitrogen-rich litter behind.

The green stems are angular, with five raised ridges running their length, and they photosynthesise long after the leaves have gone. The leaves themselves are trifoliate low on the stems and simple higher up, and they are shed early, leaving the plant to run on stem tissue through the dry part of the year.

Before the plant was a weed it was a tool. Bundles of broom stems bound to a handle made the besom, the stiff yard broom that gave the plant its common name, and the same material went into thatch, fence panels and the rough roofing of sheds and stacks in Britain.

Because broom arrived without its natural enemies, programmes in North America and New Zealand have introduced insects from Europe to feed on it. The broom twig miner lays its larvae inside young stems, the broom bruchid beetle destroys developing seed, the broom psyllid sucks sap from the shoots, and the broom gall mite deforms the growing tips. Together they reduce flowering and vigour.

Cut broom in late spring at first flowering and it is far less likely to coppice than if you cut after the seed has set. Fire is the trap: a hot burn clears the top growth and then triggers a mass of seedlings from the soil bank, so burning without follow-up makes the stand denser.

Science & Biotechnology

The genus makes quinolizidine alkaloids, and cytisine is the one that matters here. It is concentrated in the seed and is a potent nicotinic acetylcholine receptor agonist, which is why broom seed is dangerous to livestock and to anyone who treats the plant as a salad.

Sparteine was isolated from broom and became a drug in its own right, used in the nineteenth and twentieth centuries as an antiarrhythmic and in obstetrics. It was later withdrawn from routine clinical use after reports of serious reactions.

Uses & Benefits

Scotch broom was carried around the world deliberately: as an ornamental, as fodder, as hedging and as a nitrogen fixer for poor land. In New Zealand and the Pacific Northwest it escaped the garden and the farm, and because it establishes on disturbed ground and produces enormous quantities of long-lived seed, it spread faster than control programmes could follow, forming dense stands that exclude grazing and carry fire into plantations.

Flowers are typical pea flowers, bright yellow and produced along the young stems. They are pollinated by bees. Each pod ripens to black and splits explosively, flicking the seed away from the parent. The seed coat is hard and impermeable, and seed can lie in the soil for decades before it sprouts.

Growing from Seed

The hard-coated seed can remain capable of sprouting after decades buried in soil, so a site cleared of mature bushes will keep producing seedlings for years. Any realistic control programme therefore combines cutting or pulling before the pods ripen with follow-up treatment of the seedlings.

Scarify the hard seed coat with a file or hot water and sow onto a prepared surface in autumn, covering only lightly, since the seed needs moisture and the winter cold helps to soften the coat. Do not enrich the ground and do not irrigate. Judge establishment by size rather than by the calendar: once the main stem has reached about knee height and has begun to branch, the plant needs nothing from you.

Our Take

Grow broom where nothing else will grow, and then watch it. In Britain it is a valuable native, but in New Zealand and the Pacific Northwest it is a declared problem and should not be planted. If you want the same sulphur-yellow display on poor ground, Ulex europaeus is tougher still and just as heavily armed. On better soil Robinia pseudoacacia fixes nitrogen in the same way but grows into a tree, while Lotus corniculatus gives you the legume biology in a form you can mow.

Tree Seeds / Tree / Tree Seeds