Siberian squill

A vigorous, semi-evergreen, clump- and colony-forming hardy geranium grown as one of the best groundcovers for dry shade under trees and shrubs. Its soft, deeply lobed, strongly aromatic leaves form a dense, weed-smothering carpet, many of them flushing red and bronze in autumn, and above the foliage rise loose clusters of magenta-pink (or white) flowers with prominent protruding stamens in late spring and early summer. It spreads steadily by thick surface rhizomes into a tough, low-maintenance, weed-proof mat that is easy to pull back and is not aggressively invasive. The aromatic foliage makes it markedly deer- and rabbit-resistant, and it is genuinely drought-tolerant once established. It is grown purely as an ornamental and is not a food plant.

A tough, aromatic garden hybrid (Nepeta racemosa x N. nepetella) that forms a low, spreading mound of scalloped gray-green leaves topped by raceme-like spikes of two-lipped lavender-blue flowers from late spring into fall. Sterile and clump-forming rather than weedy, it shrugs off heat, drought, and deer, draws bees all season, and is mildly attractive to cats - a workhorse for border fronts, edging, and dry sunny sites.

A sturdy, upright hardy perennial grown for the dense terminal heads - and tight axillary clusters - of upward- and outward-facing, deep violet-blue (sometimes white or purple) bell-shaped flowers it carries from early to midsummer above clumps of rough, oval basal leaves. POWO (Kew) gives its native range as a broad sweep of the temperate Northern Hemisphere from Britain across Europe and through temperate Asia to Japan and Korea (some 57 botanical countries), where it grows in dry grassland, scrub, and open woodland, often on chalky soils. It is one of the easiest border bellflowers: hardy in USDA zones 3a-8b and rated fully hardy (H7) by the RHS, which gives the rich-blue cultivar "Superba" and the pale "Caroline" its Award of Garden Merit. Plant it in full sun or light shade in ordinary, moisture-retentive soil and it will spread steadily by underground rhizomes to form a colony - vigorous and welcome in a relaxed border, but worth siting where it can run, or lifting and dividing to keep it in bounds. The open clusters are excellent for bees, worked above all by bumblebees. Sources give no edible use, so treat it as an ornamental only.

A low, clump-forming native woodland violet of eastern North America, grown for its early spring blue-to-purple flowers with conspicuous white throats held over glossy, heart-shaped leaves. It does not run, but self-seeds freely - to the point of being weedy in rich, moist ground. A larval host for fritillary butterflies and a nectar source for early bees and butterflies; the leaves are high in vitamins A and C.

Common houseleek, or hens-and-chicks (Sempervivum tectorum), is an evergreen alpine succulent that forms tight rosettes of fleshy, pointed leaves, each rosette (the "hen") ringed by smaller offset rosettes (the "chicks") on short runners. Barely a few inches tall, it spreads into a low mat and thrives in the harshest hot, dry, sharply drained spots: gravel, walls, sink gardens, and the tiled roofs it was once planted on. In summer a mature rosette sends up a stout stalk of star-shaped reddish-purple flowers, then that rosette dies, leaving its chicks to carry on. It is one of the toughest, most cold-hardy, most forgiving plants there is, asking only for sun and drainage and resenting nothing so much as wet, rich soil.

The true wild primrose of European woodland and hedge banks - low rosettes of crinkled, tongue-shaped leaves throwing up many single, pale soft-yellow flowers with a deeper yellow eye, one per slender stem, among the very first blooms of the year in late winter and early spring. This is the genuine species (gentle pale yellow), NOT the loud multi-coloured Polyanthus and Primula hybrids sold as winter bedding. POWO (Kew) places it native across western and southern Europe, North Africa, and southwest Asia; RHS holds it with the Award of Garden Merit and rates it fully hardy. Its flowers and young leaves are edible, and it is a crucial early nectar source for the first bees and butterflies.