Sizing an espalier frame for fruit trees is an interesting task. And it partly makes you be honest with yourself when it comes to ‘how successful this project will be in the future”. At the start (assuming small young trees), you don’t need much strength. Its when the project is successful, in a few years, after a wonderful spring with lots of rain, resulting in a massive harvest that you REALLY need the strength for when the cyclone hits. Because once the frame breaks, there will not be any repairing – most likely a complete rebuild and replant (unfortunately).
So the Espalier Frame needs to be strong because trees are woody (heavy) and espalier (through trimming) takes away the tree’s ability to respond to stress/weight by growing appropriately. Ergo the wire and the mounting points must support a great deal of the tree’s weight – and its worse when a great fruiting season arrives…
So assuming solid end points, a low exposure profile to wind and rain, and a lateral/intermediate wire support about every 1M, then this is the recommended wire rope sizing sufficiency guide. If your exposure is high (top of a hill or in a known cyclone or storm area), then use the next size up recommended wire rope in the chart.
So If the tree is kept
- Small (< 1M), then use 2mm wire rope
- Medium (< 2M), then use ~3mm wire rope
- Large (< 3M), then use ~4mm wire rope.
- Huge (> 3M), then use ~5mm wire rope.