ABSTRACT
Floriferous and colourful herbaceous borders are one of the major achievements of British gardeners. They require skilful understanding of the characteristics of annual, biennial and perennial plants. Environmentally, these plants are hardy, half-hardy or cold-sensitive, depending on seasonal low temperature conditions where they are grown. Differing types of herbaceous plant have their natural origins in a wide diversity of geographical zones and have been brought to gardens from around the world by plant hunters. Gardeners manipulate the husbandry of herbaceous plants in accord with these differing origins. Growing ornamental herbaceous plants provides examples of the intricate relationship between genotype and phenotype as moderated by the environment which gardeners increasingly seek to control. Understanding how control may be achieved is the basis of skilful husbandry.
Types of herbaceous plants are described, illustrated and listed. Their cultural requirements of each category of plants are discussed. Culture ranges from the production of plants from seed, module raised plants bought from garden centres and mail-order companies, using forms of protection and with several perennial plants requires facilities for growing to maturity in nursery beds.
The planning and planting of borders is discussed and related with using plants of differing seasonality as, for example, biennials which are raised from seed or purchased as modules or bare-root transplants. These may require overwintering which stimulates flowering in the following spring. The vegetative propagation of herbaceous perennial plants is described and illustrated by reference to Campanula spp. Herbaceous plants are used in the garden in borders, patio and piazza containers, hanging baskets and are increasingly popular as green walls.
A detailed description of the effects of day length, and more importantly night length, on flowering is provided and illustrated. These responses result from the perception of night and day length in processes termed “photoperiodism”. Short-day, long-day and day-neutral flowering responses are considered in relation to the interchange between the red- and far-red states of the hormone phytochrome. There is consideration of other environmental factors such as the availability of water and changes in temperature which also stimulate flowering. Acclimatisation (acclimation) and dormancy are discussed as reactions that alter flowering responses. Adverse responses caused by stressful environmental factors are discussed such as excess water or its limitation in droughts, light, high and low temperature, nutrient deficiencies and toxicities, absence of support and noxious gases. These result in stressful conditions which limit plant growth and productivity. Forms of stress are discussed and parallels drawn with similar symptoms and responses in animals, and in particular with humans.
