This section is from the book "Handbook Of Hardy Trees, Shrubs, And Herbaceous Plants", by W. Botting Hemsley. Also available from Amazon: Handbook of hardy trees, shrubs, and herbaceous plants.
Deciduous shrubs, differing from the last genus in having larger often sweet-scented flowers, 4 or 5 imbricate petals, numerous stamens, and slender filaments. The species, of which there are about twelve, are natives of Central Europe, Himalayas, Japan, and North America. The Greek name of a shrub. These beautiful hardy flowering shrubs are popularly known under the name of Syringa (Seringat, French) or Mock Orange.
1. Ph. coronarius. - This is the common European species, of which there are several varieties in cultivation, including a double-flowered one, and one with variegated foliage. It grows from 4 to 8 feet high, with ovate acuminate serrulate glabrescent leaves and racemes of creamy-white fragrant flowers, appearing in May.
2. Ph. Gordonianus (fig. 99). - A very handsome and desirable American species with flowers nearly double the size of those of the common one. This does not bloom till the latter end of June or beginning of July.
Fig. 99. Philadelphus Gordoaianns. (1/4 nat. size.)
3. Ph. grandiflorus, syn. Ph. speciosus, Ph. latifolius, etc. - A shrub 6 to 10 feet high. Leaves pubescent when young, ovate-acuminate or nearly rotundate, irregularly toothed.
Flowers white, large, sweet-scented, appearing in June or July North America.
4. Ph. inoddorus. - In this species the leaves are quite glabrous, very obscurely toothed, acuminate and ovate or lanceolate in outline. Flowers white, large, scentless, terminating the short lateral branches. This blossoms about the same time as the last. North America. Ph. Lewisii and Ph. hirsutus are also North American species. These have smaller flowers, and the latter is a very dwarf hairy shrub. Ph. Satsumi, syn. Ph. Chinensis, is a slender-growing species with long narrow leaves and large white flowers; from Japan.