Spiraea thunbergii
Also known as Baby’s breath spirea is a graceful and wispy little shrub with a very fine texture – even by spirea standards. The slender wiry branches arch outward and nod downward, forming a twiggy, multistemmed mound 5-6ft (1.5-1.8 m) tall and about as wide. The semideciduous pale green leaves are thin and wispy, too; they are almost linear, a little more than 1 in (2.5 cm) long and 1/4 in (0.6 cm) wide, with a few coarse teeth along the margins. The dainty pure white five-petaled flowers are borne singly or in clusters of two or three along the stems. They are about a 1/3 in (0.8 cm) across and appear before the new leaves in late winter or early spring, often covering the whole shrub.
Yukiyanagi means snow willow in Japanese. Also known as Spirae thunbergi native to Japan. In bloom everywhere, and in our garden too.
Baby’s breath spirea blooms on the previous season’s growth, so do any pruning immediately after flowering, before next year’s flower buds develop. Remove old, nonproductive stems at ground level to stimulate vigorous new growth and to keep the plant from becoming too leggy and open. Never shear a spirea across the top. Cut out dead stem tips anytime of year.
Baby’s breath spirea performs best in full sun, but does quite well in partial shade, especially in warmer climates. Baby’s breath spirea likes a well drained soil and has ordinary water requirements. It tolerates summertime dry spells well. Baby’s breath spirea is an extremely hardy little shrub and one that may not lose its leaves in mild winters. This spirea blooms most profusely in cooler climates, usually flowering all at once in a splendid profusion of white blossoms. In the South, baby’s breath spirea tends to start blooming sporadically in January or February and the flowering season is more spread out.
Spireas are easily propagated from cuttings of green tip shoots taken in late spring and summer and rooted with bottom heat in a closed container; or from mature wood cuttings taken in autumn and rooted in a cold frame. Baby’s breath spirea also can be propagated by dividing the root clump.
Baby’s breath spirea is a long lived little shrub with a very fine texture in the landscape. It forms a beautiful mound of gracefully arching stems covered, in late winter or early spring, with tiny snow white flowers. In the summer, the pale, almost yellowish green foliage contrasts nicely with that of darker green shrubs. Any of the spireas are excellent in mixed shrub borders. Baby’s breath spirea is at its best as a specimen shrub alone or in a small group.
The genus is spelled Spiraea, but the common name drops an a and is spelled spirea. There are some 90 species of spireas occurring naturally in Europe, North America and Asia. Baby’s breath spirea is the earliest flowering of the spireas. Source: Floridata
NATURE IN JAPAN 
This is a great post in terms of information and writing quality!
… but it does leave me with a couple of questions. I don’t remember hearing of this variety before: is baby’s breath spirea also known as bridal wreath spirea – I do see you’ve got the latin name, so I guess I can look it up myself.
It would be helpful if you quoted the zones in addition to using phrases like ‘in the south’ and ‘warmer climates’.
Thank you for your comments! We don’t use zones because we’re located in Japan and the climate is somewhat different than in the U.S. Sorry!
Oh, well thanks anyhow. Since zones are used in the US and England as well as here in Canada, I’d sort-of assumed that they were an index used everywhenre.