Service horticulture

In contrast to the production of plants for food and flowers, those in service horticulture (embracing the many facets of landscaping, professional gardening and turf culture) are engaged in plant selection, establishment and maintenance. This will mainly involve:

• trees and shrubs;
• hedges, windbreaks and shelter belts;
• climbing plants;
• decorative annuals, biennials, perennial plants;
• ground cover;
• alpines;
• ornamental grasses and turf for lawns or sports surfaces.

Many will be involved in aspects of garden planning such as surveying and design.

Site requirements
For many aspects of this part of horticulture these will be similar to that for the production of plants, but it is much more common to fi nd that the choice of plants is made to fi t in with the site characteristics, i.e. 'go with the flow'. This is because the site (the garden, the park, the recreational area) already exists and it is often too expensive to change except on a small scale, e.g. for acid loving plants Rhododendron and Ericaceous species. The characteristics of the site need to be determined when planning their use and (as for outdoor production) this will include climate, topography, aspect, soil(s), drainage, shade, access, etc. However, there will often be more consideration given to view lines, incorporating existing features of value and accommodating utilities such as sheds, storage, maintenance and composting areas.

Design
Substantial plant knowledge is needed to help fulfil the principles of design which encompass:

• unity (or harmony); this is ensuring that there are strong links between the components, i.e. the individual parts of the design relating to each other. This encompasses all aspects such as continuity of materials, style or ideas (e.g. 'Japanese', 'chic' or 'rural');
• simplicity; to bring a sense of serenity, avoiding clutter by limiting the number of different materials used and repeating plants, colours and materials around the garden;
• repetition of shapes, materials, patches of colour to ensure unity, but also in order to introduce rhythm by the spacing and regularity of the repetition (see Figure 1.10);
• focal points are features of the garden that draw the eye, such as statues, furniture and individual plants, only one of which should be noticeable at a time. These are used to create a series of set pieces for viewing and to move the viewer through the garden;
• scale; plantings, materials, features, patio and path sizes should be in proportion with each other, e.g. only small trees are likely to look right in small gardens;
• balance can be achieved most easily by developing a symmetrical garden, but success with other approaches is possible by considering less formal ways of balancing visual components, e.g. groups of evergreens with deciduous trees; ponds with lawns; several small plants with a single shrub; open area with planted areas;
• interest; much of the interest is related to the selection and grouping of plants based on their form, colours and textures.

Decisions need to be made with regard to the overall style to be achieved. The need for unity suggests that mixing styles is to be avoided or handled with care. This is particularly true for the choice between formal and informal approaches to the garden or landscape.

Propagation
Nursery stock growers specialize in propagating plants which are sold on to other parts of the industry. Other parts of the industry may also propagate their own plants. Plants can be grown from seed, from division, layering, cuttings, micro-propagation, grafting or budding (see vegetative).
Sources of plants
The source depends on the type and quantity, but is usually from specialist nurseries, garden centres or mail order, including the Internet. Plants are supplied in the following ways:

• Bare rooted plants are taken from open ground in the dormant period. Whilst cheaper, these are only available for a limited period and need to be planted out in the autumn or spring when conditions are suitable; in practice this is mainly October and March. Roots should be kept moist until planted and covered with wet sacking while waiting. Plants received well before the time for permanent planting out should be 'heeled in' (i.e. temporary planting in a trench to cover the roots).
• Root balled plants are grown in open ground, but removed with soil, and the rootball is secured until used by sacking (hessian). This natural material does not need to be removed at planting and will break down in the soil. This reduces the problems associated with transplanting larger plants.
• Containerized plants are also grown in open ground, but transferred to containers. Care needs to be taken to ensure that the root system has established before planting out unless treated as a bare-rooted stock.
• Container-grown plants, in contrast, are grown in containers from the time they are young plants (rather than transferred to containers from open ground). This makes it possible to plant any time of the year when conditions are suitable. Most plants supplied in garden centres are available in this form.

It is essential that care is taken when buying plants. Besides ensuring that the best form of the plants are being purchased and correctly labelled, the plants must be healthy and 'well grown' ; the plants should be compact and bushy, free from pest or disease and with appropriately coloured leaves (no signs of mineral defi ciency). The roots of container plants should be examined to ensure that they are visible and white rather than brown. The contents of the container should not be rootbound and the growing medium not too wet or dry.