A shrub of rounded, bushy habit, 6 to 8 ft high, and as much wide; branches graceful, slender, twiggy, and covered with down. Leaves oblanceolate, 3⁄4 to 11⁄2 in. long, 1⁄4 to 1⁄2 in. wide, entire, or with a few teeth towards the apex; of a lively green and glabrous above, slightly downy and rather prominently nerved beneath. Flowers 1⁄3 in. across, pure white, produced during April and May in fascicles of four to eight, each flower on a slender glabrous stalk 1⁄2 in. or so long.
A seedling of S. × multiflora (S. hypericifolia × S. crenata), raised some years before 1884; the other parent is thought to be S. thunbergii. It is the most beautiful of the spring-flowering spiraeas, being quite hardy and never failing to produce a wealth of blossom. The flower-clusters are crowded on the upper side of shoots made the previous year, forming snowy white wreaths from 6 in. to 12 in. long. It is most conveniently increased by means of layers, its slender lissom branches adapting themselves admirably to this method.
S. ‘Grefsheim’. – A shrub in the style of ‘Arguta’ but dwarfer, to about 4 or 5 ft and flowering somewhat earlier. Leaves on the season’s growths narrowly elliptic or lanceolate, narrowed at both ends, mostly quite entire, 11⁄2 to 13⁄4 in. long, about 3⁄8 in. wide, soft sea-green and at first downy above, permanently clad beneath with short appressed silky hairs. Upper flower-clusters sessile, the lower on definite leafy branchlets; pedicels downy. This spiraea arose in the Grefsheim nursery at Nes, Norway, as a self-sown seedling and was put into commerce in 1954. It is probably a hybrid between S. hypericifolia and S. cana (S. × cinerea Zab.). The spiraea grown as S. arguta nana or compacta is probably of the same parentage.