Clematis x indivisa Avalanche

The Clematis Avalanche 'Blavaal' is undoubtedly the hardiest and most reliable of the evergreen New Zealand clematises, capable of surviving brief frosts of around -8 to -10 °C (17.6 to 14°F). This variety surprises with the abundance of its white flowering, reminiscent of an avalanche of small daisies with pale yellow centers in early spring. They bloom in clusters on two-thirds of the branches of this lovely bushy climber that reaches up to 3 m (10ft) in height. Its heavily incised foliage adorns bare shrubs in winter. Whether in the ground or in pots, plant it in full sun or partial shade, in well-drained but moist soil.

The Avalanche clematis is part of a group of hybrids resulting from crosses between different species native to New Zealand (Clematis forsteri, paniculata, marmoraria), appreciated for their early and massive flowering and their highly incised, decorative foliage even in winter. These are the clematises of the cartmanii group, belonging to the Ranunculaceae family. Generally dioecious, these plants bear male and female flowers on separate individuals. The male flowers are the most spectacular, blooming on the branches of male cultivars like 'Avalanche'. For its ornamental qualities and performance in the garden, this variety has been distinguished by the Royal Horticultural Society in England.

It is a semi-woody, climbing or creeping plant that can cover an area of about 3 m (10ft) by 2 m (7ft). Its brownish branches weave and climb into neighboring plants, clinging to their support with the leaf petiole transformed into a tendril. They bear thick, deeply incised leaves, dark green and shiny, resembling parsley leaves. Flowering takes place in spring, usually in March-April, until May depending on the climate, for several weeks. Clusters of star-shaped flowers, 2 to 3 cm (1in) in diameter, with 6 petals centered on a yellow stamen heart, bloom on the upper 2/3 of the branches. The petals gradually turn from greenish white at blooming to pure white.

The Avalanche clematis thrives in the ground in our mild regions, but also grows very well in pots, which can be easily overwintered away from severe frost elsewhere. It can be used as a climber to cover small supports (trellises, obelisks, arches), as well as in containers or over walls, cascading in elegant waterfalls. It can also form a superb ground cover on a well-exposed slope, with herbaceous clematis or Sollya heterophylla, for example. Its branches like to wander in the vegetation of shrubs such as boxwood, roses, deutzias, or small conifers, which enhance its flowering.