Sweet alyssum

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.

Heather, or ling (Calluna vulgaris), is the low, wiry evergreen shrub that colours the moors and heaths of Europe purple in late summer. It grows only 4 inches to 24 inches tall in dense, spreading mats of tiny scale-like leaves, and from July to September it is covered in spikes of mauve (wild) to white, pink, or red (cultivar) flowers that draw an intense traffic of bees - the source of prized heather honey. It is beautiful, wildlife-rich, and extremely cold-hardy, but it is also a fussy plant with two non-negotiable demands: genuinely acidic soil and cool summers. The honest catches: it will not thrive on chalk or in hot, humid heat (NC State advises against planting south of zone 6), and where introduced - notably New Zealand - it has become an invasive weed.

Trailing lantana (also called weeping lantana, purple trailing lantana, or creeping lantana) is a low, sprawling evergreen shrub or subshrub from southern South America - Uruguay, Paraguay, northern Argentina, Bolivia, and southern and eastern Brazil - named for Montevideo. Unlike common lantana (Lantana camara), an upright shrub with multicolored heads, it stays 12 to 18 inches tall and spreads 3 to 5 feet on vine-like stems, making a mat of dark green, coarsely toothed leaves covered in small clusters of lilac to purple-pink flowers with yellow throats from early summer to frost, and almost all year where winters are frost-free. It is winter hardy only in USDA zones 8a-10b (in zone 8 it dies back to the ground and resprouts in spring if well mulched) and is grown as an annual or container plant in colder regions. Two cautions come first. It is poisonous: NC State Extension rates it medium severity, with toxic fruits, leaves, sap, seeds, and stems, toxic to people, dogs, cats, and horses, and Weeds Australia reports it is suspected of poisoning cattle. And it escapes gardens: NC State Extension records it naturalized in the southern United States, Hawaii, New Zealand, and eastern Australia, Weeds Australia lists it as a declared weed in Queensland, New South Wales, the Northern Territory, and Western Australia, and the UF/IFAS Assessment of Non-native Plants predicts it to be invasive and does not recommend it anywhere in Florida.

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.

Felicia amelloides is an evergreen, woody-based perennial subshrub native to a narrow coastal strip of South Africa's Western and Eastern Cape, where it colonises stabilising sand dunes, sandy flats, and rocky outcrops at 0 to 3,280.8 feet. In the garden it delivers a near-continuous flush of sky-blue, yellow-centred daisy flowers on neat mounding growth, typically 12 to 24 inches but capable of reaching about 3.3 feet, making it one of the few true blue-flowered plants for sunny pots and borders. The honest catch is frost-tenderness: it survives only light frost in sharply drained soil and collapses below about 23°F, so outside USDA zones 9-11 it must be overwintered under glass or replaced annually - a real commitment in cool-temperate gardens.

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.