Theseand perennials are extremely well known, especially the bedding plants which are actually the least attractive.
Biennials are marketed in flower as early as late winter and are planted in formal patterns. Hardy perennial species are excellent border plants and make good ground-cover. They are more modest in appearance and their colours are more attractive.
Biennials will grow in any not too poor soil. The perennial species are fairly winter-hardy, but must be planted in a very well-drained, for instance on a slight slope. Like nutritious soil.
Biennials are sown in early summer in a shady spot. They are pricked out once and transferred to their permanent position in early autumn. Fi hybrids are sown in early winter in the, and will flower in the following summer. Hardy perennials are usually increased by division.
cornuta, horned : Hardy perennial, height 15-30 cm; flowering season late spring to mid summer, occasionally it again in late summer. The following are fine strains: ‘Anneke’, violet red; ‘Amethyst’, amethyst violet; ‘Blue Perfection’, pale blue; ‘Bullion’, deep golden yellow; ‘Hansa’, blue violet; ‘Purple Bedder’, dark purple, and ‘White Perfection’, pure white. odorata, sweet violet: Height 10-20 cm; scented blue or violet-coloured in early to mid spring, often sold in small bunches. There are also white and rose-red forms. A well known variety is ‘The Czar’, violet blue, strongly scented. It develops long runners, making it mat-forming. Provide some protection against severe frost. Viola tricolor: Biennial, height 15-30 cm; may flower as early as late autumn, but the normal flowering season is early spring to early summer. The season may be prolonged if all faded flowers are removed. Forms in cultivation are also known as wittrockiana hybrids, and occur in a wide variety of colours and shapes; usually the flowers are tricoloured, blotched or edged with a contrasting shade. Dutch and Swiss Giants are still in cultivation, but the ‘Vierlander’ strains: ‘Primavera’ and ‘Hiverna’ are more modern forms. As the names imply, these are very early flowering.