Site factors affecting the design of a local orchard include soil, climate, vegetation, wildlife, topography, aspect and exposure. If they constrain the design they can be mitigated to some extent by management. Site factors can operate on a local or small scale. It is quite likely that one part of a site, even if just part of a domestic garden, is more sheltered, sunnier, has deeper soil, is less prone to frost etc. than another. This variation is at least as important as larger-scale (regional) variation.

Soil

Fruit trees grow well on diverse soils provided that they allow good root development and are well aerated. Soils subject to summer drought may restrict fruit size. The worst soils are thin, compacted, poorly drained or subject to periodic waterlogging.

 To evaluate the soil look at the topography (steep or convex slopes have relatively thin soils, while gentle or concave slopes have deeper soils) and the growth of nearby vegetation (especially trees). Dig a soil pit: good signs include a dark upper layer (suggesting the presence of organic matter), the presence of earthworms, a good depth (say to 40cm) with an uncompacted or crumbly structure that allows easy root penetration, a texture that is neither too coarse (very sandy) nor too fine (dominated by clay), and no evidence (like bluish colours) of poor drainage.

 Climate

Wetter climates have relatively little sunshine, on average wetter soils, and a higher incidence of the apple diseases ‘scab’ and ‘canker’. Varieties are preferred accordingly. The growing season is relatively short in the north, and ‘early’ and ‘midseason’ varieties, which have relatively short growing seasons, are typically favoured there.

 Altitude and topography

These site factors influence (among other things) damage to blossom from spring frosts, the biggest weather hazard in the southern and eastern parts of the country. Wind frosts are worst on exposed sites while radiation frosts, which occur on still, clear nights, are worst in hollows or where some barrier (like a fence or building on the lower side of the site) impedes the drainage of cold air. A sloping site on the other hand allows air movement, while proximity to large bodies of water (including the sea) limits the occurrence or severity of frost.

 Exposure

Exposed sites are primarily windy. Wind causes physical damage, slows growth, is bad for pollinating insects and may cause the crop to fall prematurely. Aspect is relatively important if the slope is steep or exposed. For example, a south-facing slope is relatively hot and dry in summer while a west-facing slope is likely to be exposed to westerly winds. Fences, shelterbelts, other vegetation, walls and buildings can all provide shelter and may re-radiate the heat of the sun.

 Site amelioration

Soil can be improved for fruit tree culture by digging an over-large hole for planting then back-filling with soil mixed with compost, peat, fertilizer etc. There may also be root competition from nearby vegetation which you could get rid of or reduce, whether from grass and herbs close to the planting spot or taller woody plants further away.

The microclimate of a local orchard can be influenced in numerous ways, for example by reducing shade or providing shelter, whether to reduce exposure (shelterbelt or artificial windbreak) or to protect from rain or frost. Masonry walls absorb and re-radiate heat (as well as creating shelter), so that a south-facing wall is often said to be relatively warm, but it may also be very hot and dry in summer.