Two Plants Built for a Windswept Border

If your garden faces the sea — or simply behaves as though it does — you will already know the frustration of watching tender plants shredded by salt-laden wind. The answer is not to fight the site but to plant things that evolved for it. Thrift (Armeria maritima) and sea holly (Eryngium) are two of the finest, and they look superb planted together: thrift's tight evergreen cushions of pink pom-poms low at the front, sea holly's steely blue collars and thistle-like cones rising behind them.

Both cope with poor, thin, gritty soil. Both shrug off gales and spray. Neither wants feeding or fussing over. Get them in the ground properly and they will reward you for years.

Getting the Soil and Site Right

The single most common reason these plants fail is soil that is too rich or too wet in winter. Think of a shingle beach: sharp drainage, full sun, very little organic matter. That is your target.

• Sun: at least six hours a day. Both will sulk and flop in shade.
• Drainage: essential. If your soil is heavy clay, dig in two or three generous buckets of horticultural grit per square metre and plant on a slight mound.
• Fertility: low. Do not add manure, compost or general-purpose fertiliser. Rich soil produces soft, sappy growth that snaps in the wind and flowers poorly.
• Mulch: a 5cm layer of gravel or shell grit around the plants suppresses weeds and keeps the collar of the plant dry.

Planting Thrift

Thrift is a British native, found clinging to cliff ledges and salt marshes around our whole coastline, so it is genuinely at home in the toughest spot you can offer. Plant in early spring or early autumn, when the soil is workable but not sodden.

Space plants about 30cm apart. Thrift forms a dense, mounded cushion, and a group of five or seven planted in a drift makes far more impact than a single specimen. Set each plant so the crown sits just at soil level — burying it deeper than it was in the pot is a reliable way to kill it. Water it in, then firm gently and top-dress with grit.

Named forms such as Armeria maritima 'Vindictive' or the white-flowered 'Alba' are worth seeking out, but the straight species is tough as old boots and self-seeds politely where it is happy.

Planting Sea Holly

Sea holly is the drama in the border: stiff, branching stems topped with cone-shaped flower heads surrounded by a ruff of spiny bracts, all in shades of silver, steel blue and amethyst. The flowers are superb for cutting and dry beautifully.

The key thing to know is that most eryngiums have a deep taproot and hate being moved. Plant them young, in their final position, and leave them alone. Space them 45–60cm apart, allowing for the spread of the flower spikes.

Our native Eryngium maritimum is a protected plant in the wild and rarely thrives far from shingle, so for garden borders look instead at E. variifolium, E. bourgatii, E. planum or the excellent hybrid E. x oliverianum 'Neptune'. All want the same conditions: sun, grit and neglect.

Watering Through the First Year

Once established, neither plant needs watering except in exceptional drought — thrift in particular will happily go weeks without. The first summer is different. Water deeply and infrequently, giving a thorough soak every ten days or so rather than a daily sprinkle. This encourages roots to travel downwards in search of moisture.

Stop watering entirely by early autumn so the plants harden off before winter. In their second year, leave them to it. If a sea holly looks limp on a hot afternoon, resist the hose; it will recover by evening.

Deadhead thrift lightly after its main flush in May and June to encourage a second, smaller flowering in late summer, but leave the last seed heads on the sea holly — they hold their shape well into winter and look spectacular frosted.

Dividing and Keeping the Display Going

Thrift is short-lived if left alone: the centre of the cushion goes woody and bald after two or three years. Dividing solves this neatly.

• Lift the clump in early spring, just as new growth starts.
• Break or cut it into sections roughly the size of your fist, discarding the tired woody middle.
• Replant the healthy outer rosettes into refreshed, gritty soil and water them in.
• Repeat every two to three years — you will never need to buy another thrift.

Sea holly is a different matter. Because of that taproot, division almost always kills it. Propagate instead by taking root cuttings in winter, or sow seed in autumn and leave the pots outside to be chilled by the frost, which the seed needs in order to germinate. Seedlings can be moved while tiny and planted out the following spring.

Get these two right and your coastal border will look after itself: silver, blue and pink, standing up to whatever the weather throws at it.