- In the UK the most favourable sites are likely to be those at altitudes between sea level and 125 metres above sea level.
- Depending on site topography, wind speed tends to increase whilst temperature and sunshine decrease with increasing altitude.
- Although it would seem that crops such as sweet cherry grow better on south or south westerly aspects, there is no supporting evidence to suggest that apples are similar in this respect.
- A site with a slight slope is recommended, as this allows the steady flow of cold air down the slope away from the trees and gives some protection to their vulnerable flowers during frosty weather at flowering time.
- No barriers to this flow of air should be permitted, such as ill-sited windbreaks.
- Sites in valley bottoms (often called ‘frost pockets’) should be avoided, as these tend to be prone to frost damage in the spring.
- Sites close to lakes or other large bodies of water can reduce the incidence of frost damage.
Meteorological records taken in previous years can aid greatly in site selection.
- Particular attention needs to be given to the incidence of frost, likely wind speeds and daytime temperatures during the April and May flowering period.
- Temperatures at flowering time of less than -2oC, (at approximately 0.5m above ground level) cause significant damage to the flowers if sustained for one hour or more.
- Although some varieties will set fruits when daytime temperatures are as low as 5oC (e.g. Falstaff), the majority of scion varieties require daytime temperatures of 12-15oC for successful pollen germination and growth.
Previous successful fruit production on a site is not always a good guide for the future.
- Destruction of woodland or the removal of surrounding plantings of large trees or hedgerows in an area can change its climatic suitability significantly.
- Also, global warming is now recognised as a real phenomenon and this may, in future, change the suitability of traditional sites for apple production.
- Unfortunately, the anticipated consequences to weather patterns in the UK are less well known, currently.
- If future predictions suggest the incidence of stronger winds and/or more spring frosts, even more care will need to be taken when selecting sites.
Summary
- Choose a site which is between sea level and 125 metres above sea level.
- Choose a site which has a slight slope to allow the escape of cold air flows.
- Ensure that there are no barriers (buildings or windbreaks) which impede the movement of cold air off the site and create ‘frost pockets’.
- Sites close to large bodies of water tend to be slightly warmer and less sensitive to frost damage.
- Choose a site which is sheltered from strong winds.
- If available, study meteorological records taken on the site in previous years. Avoid low temperature sites.