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.
Herbs or undershrubs, usually glabrous. Leaves alternate, opposite or radical, serrate or dentate; petiole often glandular at the base. Peduncles axillary, solitary, or fascicled, one or more flowered. Flowers irregular. Sepals 3, very rarely 5, coloured, imbricated, two lateral flat, two anterior when present small, the posterior or upper produced downwards in a spur. Petals 3, anterior outside, concave, lateral, bifid, formed of two united, the upper lobe exterior. Stamens 5. Capsule 5-celled, many-seeded, the valves opening with elasticity; seeds exalbuminous. About 140 species are known, chiefly from tropical Asia.
1. I. Balsamlna (fig. 61). Common Balsam. - This familiar annual is of Eastern origin. In a wild state it is a very hand-some plant with rosy-red flowers; but under cultivation it has given birth to a number of varieties differing to an almost incredible degree from the ordinary type. The flowers are regular and very double in the most esteemed strains; white, cream, yellow, lilac, violet, pink, rose to dark crimson in colour; and there are also striped and spotted varieties. Florists distinguish pyramidal dwarf and camellia-flowered races. This is sometimes employed for bedding or mixed borders in sheltered situations, and is very effective; but to get it in perfection it must be grown in pots.
Fig. 61. Impatiens Balsamina flore pleno. (1/4 nat. size.)
There are a few hardy annual species occasionally seen in gardens, but they are hardly worth cultivating, the flowers being small and the habit weedy. I. Noli-me-tangere, a tall yellow-flowered species, is the commonest.