This section is from the book "Beautiful Gardens - How To Make Them And Maintain Them", by Walter P. Wright. Also available from Amazon: Beautiful Gardens: How To Make And Maintain Them.
In their great range of height, season of flowering, and colouring, the Phloxes are almost unexampled among hardy flowers. While some forms are the neatest of rockery gems, others are the noblest of border plants. Some bloom in spring, others in summer and autumn.
While the tall, border Phloxes are poor, ineffective plants in hungry soils, they are magnificent when grown in a suitable medium. It is unfortunate that they are a little difficult to suit in respect to soil. They do not care for shallow soils on chalk, nor are they quite at home in clay. A deep loam suits them best. The author has had fair results on clay by thoroughly ameliorating it with burnt rubbish, decayed manure, and sand, especially, perhaps, with the coloured sorts. The whites have needed a good deal of nursing.
So beautiful are the plants when in health and vigour that it is well worth while to make special efforts to succeed with them. They look best in clumps of four or five plants. Specialists may make beds of them, and they are well worth it. If the soil is a well-drained, sandy loam, and is bastard trenched and well manured, few finer beds will be seen than those filled with the Phloxes. The tall varieties should be staked.
Propagation is easily effected, either by cuttings or division. Where the plants are quite at home, and form large clumps, the latter process is advisable; but where they are struggling for existence it is best to increase the stock by cuttings of the young shoots in spring. Even if propagation is not desired strong clumps should be divided occasionally, and the shoots thinned annually. The former prevents impoverishment of the soil, the latter ensures fine flowers.
The Phloxes have been a good deal intercrossed, but at least four sections stand out fairly clearly: (1) the annuals, varieties of Drummondii, which are best raised from seed in spring; (2) the dwarf Alpines or trailers; (3) the early summer border perennials, or suffruticosa section; and (4) the late perennials, or decussata section.
The dwarf, spring-flowering Phloxes are charming flowers for rockwork, edgings, or the fronts of borders. Divaricata is a pretty lilac blue, spring-flowering species, averaging a foot high; there are several varieties of it, including a white. Ovata, red, is a little taller, and also a spring bloomer. Reptans, violet, is a creeping plant, and flowers in spring. But the most valuable of the dwarf, early-flowering section is certainly subulata, for not only is it pretty in itself, with its abundance of pink flowers, but it has given us a number of charming varieties, such as alba, white; compacta, pink; frondosa, rose; grandiflora, pink with crimson eye; Little Dot, pale lilac; Newry Seedling, lilac; The Bride, white with rose eye; and Vivid, rose.
The early autumn border Phloxes, most of which grow from 2 to 3 feet high, are extremely useful, as they come into bloom as the spring sorts go off. Six good varieties are Attraction, white, red eye; James Hunter, deep pink; Magnificence, rose, crimson eye; Miss Lingard, white, with lilac eye; Mrs. Forbes, white; and The Shah, purplish red.
The late varieties follow, and carry on the display until late in September. It is in this section that cross fertilisation is most active, and consequently the annual flow of novelties is strong. Of established sorts, of proved merit, the following may be grown:
Archibald Forbes, salmon rose, crimson eye; L'Aiglon, rosy carmine, dark eye; Coquelicot, orange scarlet, purple centre, old, but one of the best; Espérance, mauve, white centre; Le Mahdi, violet and blue; Le Siècle, salmon rose, lilac centre; Mrs. E. H. Jenkins, white; Mrs. Oliver, salmon; Papillon, lilac; Rossignol, rosy mauve, white centre; and Tapis Blanc, white.