lithodora

Lithodora diffusa (Boraginaceae) is a mat-forming evergreen groundcover native to southwestern Europe, from northwestern France through the Iberian Peninsula. It grows less than 1 foot tall and spreads to form low, dense mats of small, dark green, hairy leaves. In May and June, masses of intensely blue, five-lobed flowers cover the foliage.

Lithodora requires sun to part shade and well-drained, acidic soil. It resents wet winter conditions and heavy clay. Moderate water and medium maintenance (occasional trimming after bloom to maintain density) keep it looking its best. The cultivar 'Grace Ward' is widely grown for its profuse, gentian-blue flowers and compact habit. No significant pest or disease problems are documented. Generally hardy in Zones 6 to 8.