Flowering Dogwood ‘Rainbow’ · Cornus florida ‘Rainbow’

Cornus florida 'Rainbow' is a slow-growing deciduous small tree reaching 4 to 6 metres in height with a rounded, broadly spreading habit at maturity. The cultivar is distinguished from the species by its variegated foliage: leaves carry cream to yellow margins around a green centre, holding the variegation through the growing season before turning intense red and purple in autumn. White petal-like bracts surround the inconspicuous true flowers in mid to late spring, giving a second ornamental phase before the leaves fully expand.

The species is winter-hardy to approximately minus 26 °C (USDA zone 5b), but useful performance is limited less by absolute minima than by the need for warm, humid summers to ripen wood and by sensitivity to late spring frosts on the variegated foliage. Heat tolerance is moderate; performance above 35 °C requires root run in cool, organically rich soil and afternoon shade. Drought tolerance is low, and the species is sensitive to saturated soils, so site drainage and consistent summer moisture are both selection variables.

Reliable across Atlantic and warm-temperate continental Europe, including coastal northwest Europe, the Po valley, and warmer pockets of central Europe. Not recommended for the inland Pannonian basin or sites east of a line through Berlin without sheltered microclimate, nor for hot dry continental Mediterranean exposures without supplementary irrigation. Coastal positions exposed to salt-laden wind are unsuitable.

Crown density is moderate and the layered horizontal branching reads as architectural in winter, which suits specification as a courtyard or entrance specimen rather than a canopy tree. The cultivar prefers slightly acidic, well-drained loams in partial shade; alkaline or compacted urban soils shorten its useful life. Specifiers familiar with Cornus kousa will recognise the role; 'Rainbow' contributes variegated foliage and earlier flowering at a comparable scale.

Dogwood anthracnose (Discula destructiva) remains the principal disease pressure on C. florida in cool, humid conditions, with powdery mildew secondary; healthy planting stock and air movement at the site mitigate both. Specified as a focal specimen near patios, woodland edges, or small private gardens, the cultivar earns its place through sustained seasonal interest rather than canopy contribution.