The reliably hardy perennials

These are the salvias you plant once and forget about. Salvia nemorosa and its cultivars — 'Caradonna', 'Ostfriesland', 'Amethyst' — form tidy clumps that erupt in spikes of violet-blue from June through August if you deadhead them. They want full sun, tolerate clay and chalk, and ask only that you cut them to the ground in late autumn or early spring. Height sits around 45–60 cm. They are utterly unfussy.

Salvia × sylvestris behaves almost identically but flowers slightly earlier and holds its stems more stiffly upright. Salvia pratensis, the meadow clary, is the wild British native — taller at 90 cm, looser in habit, with paler flowers that seed about if you let them. Salvia verticillata 'Purple Rain' is the least formal of this group, with whorled flowers and a sprawling, cottage-garden charm. All four types are rated to -15°C or lower. They will survive a Yorkshire winter without mulch.

The maintenance calendar is minimal. In March, cut last year's stems to 5 cm above ground level before new growth starts. By mid-May, the clump is knee-high. After the first flush of flower in late June, shear the whole plant back by half — you will get a second, slightly shorter flush in August. No staking, no fuss, no lifting. These are the salvias that make you look competent.