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.
Annual or perennial herbs with cordate, sagittate or lobate leaves and solitary or racemose axillary showy flowers with or without conspicuous bracts. Corolla funnel- or salver-shaped, plaited. Capsule 2-celled; cells usually 2-seeded. A large genus comprising nearly 100 species, found in temperate and tropical regions. The name is from the Latin convolvo, to entwine.
Our native species of Convolvulus are all perennial and very handsome, though they are too common to gain many admirers. C. arvensis is the creeping species with white or pink flowers, often a great pest in cultivated ground; C. sepium is the large white-flowered plant of hedgerows; and C. Soldanella is a trailing maritime plant with pink or pale purple flowers.
1. C. tricolor (fig. 177). - This charming little South European annual is the Convolvulus minor of seedsmen.
Fig. 177. Convolvulus tricolor. (1/4 nat. size.)
Description is hardly necessary. Suffice it to say that it is a decumbent plant with silky foliage and large solitary tricoloured flowers. The centre of the flower is yellow, followed by a white band, and is bordered with deep blue in the common variety; but there are several garden varieties variously striped with some or all of the above colours, and others in which violet enters. There is also a double-flowered variety.
C. althceoides is a twining perennial species from the South of Europe, with silvery lobed or dissected leaves and delicate rose-coloured flowers borne in pairs. C. pubescens, syn. Galystegia pubescens, is another twining species with hastate downy leaves and large flesh-coloured flowers. The variety in cultivation lias very double flowers and is very showy, but hardly suitable for planting in a border on account of its running roots. It is reported to come from China. C. Dahurica has cordate leaves and handsome deep rose-coloured flowers. The species formerly referred to Calystegia have two large leafy bracts overlapping the calyx.