An Asiatic group of deciduous shrubs allied to Philadelphus, but very distinct from that genus in having ten stamens with winged stalks, often toothed or forked at the top; in the starry hairs or scurf with which most parts of the plants are furnished; and in five (instead of four) petals and calyx-lobes. Leaves opposite. Flowers either in racemes, as in D. gracilis and scabra, or in corymbose panicles.
The deutzias are some of the most beautiful shrubs flowering in June. Nearly all the species mentioned in the following descriptive notes are quite winter-hardy; but, unfortunately, some deutzias are easily excited into growth by unseasonable warmth in the early spring months, and are often, especially in low-lying districts, injured and their crop of flowers ruined by late frosts. This is true in particular of D. gracilis. D. × lemoinei and D. setchuenensis. But D. longifolia, D. discolor, D. purpurascens, D. scabra and their hybrids give no trouble in this respect. Deutzias like a good loamy soil and plenty of moisture; most are lime-tolerant. The only pruning required is an occasional (say biennial) thinning out of the old worn-out branches. As they flower on the shoots made the previous year, no shortening back can be done except at the loss of bloom. They are very easily propagated by cuttings of half-ripened wood placed in gentle bottom-heat about the end of June or later.
The genus was named after Johann van der Deutz who lived at Amsterdam in the 18th century and was a friend and patron of Thunberg.
From the Supplement (Vol. V)
Some references are made below to the monograph of Deutzia by the Russian botanist T. I. Zaikonnikova, published in Leningrad in 1966. A translation of the key in this work will be found in Baileya, Vol. 19, pp. 133-44 (1975).