Blue daisy bush

Aubrieta (Aubrieta deltoidea) is a low, mat-forming evergreen perennial in the mustard family (Brassicaceae), native to the rocky hillsides of southeastern Europe - primarily Greece, the Aegean Islands, Crete, and adjacent Mediterranean coasts. It is one of the most reliable spring-flowering ground covers for sunny, well-drained spots: cascading sheets of violet to deep pink four-petalled blooms from March through May, attractive to bees and bee flies. The honest catch is that without a hard cut-back immediately after flowering, plants become woody and bare in the centre within two or three years, collapsing from a tight carpet into a tired, gappy mat.

Campanula carpatica is a low, mounding herbaceous perennial native to the rocky subalpine habitats of the Carpathian Mountains, ranging across Poland, the Czech Republic, Slovakia, Romania, and Ukraine (Wikipedia). Its wide, upward-facing bell flowers in violet-blue, white, or pink appear from June through August, making it one of the longest-blooming edging perennials available, and it holds an RHS Award of Garden Merit. The honest catch is longevity: it tends to behave as a short-lived perennial, often thinning or declining after a few seasons, so gardeners should plan for regular division or fresh plants from seed to hold the planting.

Bulbine frutescens is a fast-growing, clump-forming evergreen perennial from southern Africa, grown for its grey-green, fleshy, almost grassy succulent leaves and near-continuous spikes of star-shaped yellow or orange flowers tipped with distinctive fluffy stamens. It spreads readily by rooting low stems to form a dense, drought-tough groundcover (roughly 4 to 20 inches tall but 3.3 to 4.9 feet wide), making it a strong choice for sunny borders, dry banks, gravel gardens and containers. The clear leaf gel is a well-known folk remedy applied topically to burns, blisters, insect bites and minor skin irritations, and the plant is regarded as non-toxic to people and pets. The load-bearing caution is frost-tenderness: RHS rates it H3 (hardy only to about 23 to 34°F), so outside roughly USDA zones 9b-11 it must be grown in containers and overwintered frost-free or treated as a tender bedding plant. It is not known to be invasive, though its vigorous self-rooting spread means it can colonise open ground quickly in mild, frost-free climates. Give it full sun and sharp drainage and it is otherwise low-maintenance, pest-free and disease-free.

Osteospermum jucundum (the trailing or delightful African daisy) is a low, mat-forming to sprawling evergreen perennial in the daisy family (Asteraceae) from the mountains of southern Africa, prized for its profusion of magenta-pink to mauve-purple daisy flowers with dark central eyes over a long summer-to-autumn season. It spreads by creeping rooted runners to form a groundcover or to cascade over walls and rocks, making it a strong front-of-border filler, edging, and container trailer. Note that Kew's Plants of the World Online now treats the accepted name as Dimorphotheca jucunda, with Osteospermum jucundum retained as a synonym and the name still in wide horticultural and RHS use. The load-bearing caution is frost-tenderness: the RHS rates it H3 (half-hardy, roughly USDA 9-11), so in cold-winter climates it needs a sheltered, well-drained spot or is grown from overwintered cuttings. It is only minor-toxicity (RHS lists it as potentially harmful if eaten) rather than seriously poisonous, and it is not known to be invasive, though it has naturalized locally in mild regions such as the Isles of Scilly and Tasmania.

Cheddar pink is a low, mat-forming evergreen perennial pink (a Dianthus, not a true carnation) native to calcareous rock ledges and cliff faces across western and central Europe, from the protected population at Cheddar Gorge in England east to Ukraine. Its intensely clove-scented, fringed rose-pink flowers and blue-grey foliage make it one of the finest front-of-border edging plants in a sunny, sharply drained garden. The honest catch is drainage: in any soil that holds winter moisture the crown rots reliably, so it fails in heavy clay or irrigated beds and thrives only where drainage is sharp and the site stays dry underfoot in cold months.

Chionodoxa forbesii (syn. Scilla forbesii) is a small bulbous perennial native to western Turkey - botanically recorded only from Babadağ Mountain in Muğla Province - producing loose racemes of up to 12 star-shaped, sky-blue flowers with white centers on 4 to 6 inches stems in early to mid-spring. It naturalises freely under deciduous trees and in lawns, filling gaps with carpets of colour before most other plants wake from winter, which is its genuine garden gift. The honest catch is its eagerness to spread: it seeds prolifically and the bulbs multiply quickly, so in a small garden or a formal bed it can crowd out neighbours and become hard to contain once established. All parts are toxic if eaten, and the bulbs need a dry summer dormancy or they rot.