How to Grow Broom Shrubs in a Coastal Garden

Why Broom Belongs by the Sea

Broom is one of those plants that seems to have been designed with the coast in mind. Its tiny leaves are really just slivers, with most of the work of photosynthesis carried out by green, wiry stems. That reduces the surface area exposed to salt-laden wind and cuts water loss to a minimum, which is why a plant that looks delicate in flower can shrug off a gale coming straight off the sea. Get broom right and it rewards you with a solid fortnight of colour in May and early June, followed by a summer of neat, dark green architecture.

The genus covers a useful range. Cytisus scoparius is our native broom, upright and quick-growing, with yellow flowers and a fair amount of self-seeding. Cytisus × praecox hybrids are the ones most coastal gardeners should look at first: compact, slightly later to flower, and generous with cream, primrose or lilac blooms. There are also prostrate forms for windy front-line positions and taller selections for the back of a border.

Choosing the Right Broom for Your Plot

Exposed seaside plots vary enormously. A garden twenty metres from the shingle takes far more punishment than one tucked behind a hedge two streets back. Match the plant to the spot:

• Front line, salt and wind: prostrate broom, Cytisus decumbens, or dwarf forms of Cytisus × praecox. Keep them low and let the wind pass over.
• Mid-border: 'Boskoop Ruby', 'Allgold' and 'Andreanus' all flower freely and stay manageable at around a metre to a metre and a half.
• Back of a border or against a warm wall: taller Cytisus scoparius selections, though be aware they may need replacing after a decade.
• Chalky soils: choose with care. Broom prefers acid to neutral ground and can yellow on very alkaline chalk. If that is what you have, work in plenty of leaf mould and consider a raised bed.

Planting: Getting It Right First Time

Broom has a long taproot and resents being moved, so the planting hole is the one chance you get. Buy the smallest plant you can reasonably handle — a nine-centimetre pot will usually overtake a three-litre one within two seasons and establishes far better.

Plant between October and March, but wait for a mild, dry spell rather than working in sodden winter ground. Dig a hole a little wider than the rootball but no deeper, and mix in a couple of handfuls of garden compost or leaf mould. Do not add fertiliser. Rich soil makes broom sappy, floppy and reluctant to flower; lean conditions are exactly what it wants.

Set the plant so the top of the rootball sits level with the surrounding soil, firm it gently with your boot rather than your thumbs, and water well. On an exposed site, stake with a short cane for the first year — enough to stop the roots rocking, not so rigid that the stems cannot flex and toughen.

Watering, Feeding and Aftercare

For the first summer, water thoroughly once a week in dry spells. After that, established broom rarely needs watering at all, and overwatering is far more likely to kill it than drought. In heavy clay, plant on a slight mound so the crown never sits in standing water.

Mulch in spring with two to three centimetres of gravel, bark or well-rotted compost, keeping it clear of the stems. That is the whole feeding regime. If a plant looks tired and pale, a light scatter of general-purpose feed once a year is plenty; more than that does harm.

Broom is short-lived by nature — ten to fifteen years is a decent innings. Take cuttings in late summer, or collect seed in August, so you always have a replacement coming on. Do not try to divide or move an old specimen.

Pruning for Shape and Longevity

This is where most broom is lost. The rule is simple: prune immediately after flowering, and never cut into bare, leafless old wood. Those old stems will not reshoot.

• Start in the plant's second year, trimming flowered shoots back to within a few centimetres of the older framework.
• Work with secateurs rather than shears, so you can see where each cut lands.
• Remove one or two of the oldest stems at the base each year to encourage fresh growth from low down.
• Deadhead spent flowers if you want to reduce self-seeding about the garden.

Light shaping in the first two or three years builds a dense, bushy plant that flowers from top to bottom. Miss those early years and you will be left with a leggy specimen that only performs at the tips.

Troubles, Pests and Good Neighbours

Broom is largely trouble-free, but watch for broom gall mite, which causes knobbly, tufted growth on young shoots, and for aphids on soft tips in early summer. A sharp spray of water usually deals with the latter; badly affected stems are best cut out and binned.

Companions should share its tastes: sharp drainage, sun and lean soil. Rosemary, lavender, sea buckthorn, tamarisk, hebe and ornamental grasses all knit together well. Underplant with thyme or stonecrop to cover the ground while the broom's woody base thickens up.

With the right spot, a careful first planting and a firm hand with the secateurs each June, broom will give you decades of reliable spring colour in conditions where little else dares to grow.