Horticulture, the branch of plant agriculture dealing with garden crops, generally fruits,vegetables, and ornamental plants. The Horticulture falls between domestic gardening and field agriculture, through all forms of cultivation naturally have close links.

It is divided into the cultivation of plants for food and plants for ornament. Pomology deals with fruit and nut crops. Oliericuture deals with herbaceous plants for the kitchen, including, for example carrots, cauliflower. Floriculture deals with the production of flowers and ornamental plants; generally, cut flowers, pot plants, and greenery. Landscape Horticulture is a broad category that includes plants for the landscape, including lawn turf but particularly nursery crops such as shrubs, trees, and vines.
The specialisation of the horticulture and the success of the crop are influenced by many factors. Among these are climate, terrain, and other regional variations.

HORTICULTURAL REGIONS :

TEMPERATURE ZONES :

Temperature zones for horticulture cannot be defined exactly by lines of latitude or longitude but are usually regarded as including those areas where frost in winter occurs, even though rarely. Thus, most parts of Europe, North America and Northern Asia
are included, though some parts of the United States, such as southern Florida, are considered subtropical.
The temperature zones are also the areas of the grasses – the finest lawns particularly are in the regions of moderate or high rainfall- and of the great cereal crops. Rice is excluded as being tropical, but wheat, barley, corn and Rye grow well in the temperature zones.
Plants in the temperature zones benefit from a winter resting season, which clearly differentiates them from tropical plants which tend to grow continuously. Most of the great gardens of the world have been developed in temperature zones. Particular features such as rose gardens, herbaceous borders, annual borders, woodland gardens, and rock gardens are also those of temperature zone gardens. Nearly all depends for their success on the winter resting period.

TROPICAL ZONES :

There is no sharp line of demarcation between the topics and the subtropics. Just as many tropical plants can be cultivated in the subtropics, so also many subtropical and even temperature plants can be grown satisfactorily in the tropics. Elevation is a determining factor. In addition to Elevation, another determinant is the annual distribution of rainfall. Plants that grow and flower in the monsoon areas, as in India, will not succeed where the climate is uniformly wet. Another factor is the length of day, the number of hours the sun is above the horizon;some plants flower only if the day is long, but others make their growth during the long days and flower when the day is short.
In the tropics of Asia and parts of central and south America, the dominant features of the gardens are flowering trees, shrubs, and climbers. Herbaceous plants are relatively few, but many kinds of orchids can be grown.

PROPAGATION :

propagation is the controlled perpetuation of plants,is the most basic of Horticulture practices . It’s two objectives are to achieve an increase in numbers and to preserve the essential characteristics of the plant. Propagation can be achieved sexually by seed or asexually by utilising specialised vegetative structures of the plant or by employing such techniques are cutting, layering, grafting and tissue culture

SEED PROPAGATION :

The most common method of propagation for self- pollinated plants is by seed. In self-pollinated plants,the sperm nuclei in pollen produced by a flower fertilize egg cells of a flower on the same plant. Propagation by seed is also used widely for many cross- pollinated plants pollen is carried from one plant to another.
The practice of saving seed to plant the following year has developed into a specialized part of horticulture. Seed technology involves all of the steps necessary ensure production of seed with high viability, freedom from disease, purity, and trueness to type. These processes may include specialized growing and harvesting techniques, cleaning, and distribution. Germination in such seed may be accomplished by treatment to remove these inhibitors. This may involve cold stratification, storing seed at high relative humidity and low temperatures, usually slightly above freezing. Cold stratification is a prerequisite to the uniform germination of many temperature-zone species such as apple, bear, and redbud.

VEGETATIVE PROPAGATION :

Asexual or vegetative reproduction is based on the ability of plants to regenerate tissues and parts. In many plants vegetative propagation is a completely natural process; in others it is an artificial one. It has may advantages. These include the unchanged prepetuation of naturally cross pollimated palnts and the possibility of propagation seedless progeny.
Vegetative propagation is accomplished be use of

1. Apomictic seed
   2. Specialized vegetatice structres such as runners, bulbs, corms, rhizomes, offshoot, tubers, stems and roots.
2. Layers and cuttimgs
3. Grafting and budding
   5. tissue culture.