If you are not necessarily looking to grow an espalier fruit tree for its fresh fruit but rather for its ornamental value, go for a quince! They are undemanding, vigorous, low-maintenance, and thrive in partial shade -- a very interesting alternative to apples, pears, and other fruits. The fruit of the quince is not delicious eaten fresh, but make great specialty jellies and marmalade!
(lat.: Cydonia oblonga)
The quince is an undemanding fruit tree, but needs a well-aerated soil that is not too heavy. It loves the sun, walls in partial shade are sufficient when it is grown as an ornamental plant. Quince can be found in local tree nurseries or ordered online.
When cultivated on an espalier, quinces are treated as shaped trees. They can grow to a height of about 6 metres, with white large flowers in May / June. The fruits are strongly scented and become edible, if at all, only on southern walls in full sun, and then only in late October or November. In other, less optimal conditions, they are still loved as a (hard and tart) economic fruit for jelly, jam, 'quince bread,' etc.. The furry skin must be removed before processing. There are "apple" quinces and "peach" quinces, depending on the shape of the fruit. One pruning to thin out the branches per year is enough.
The table at the bottom of this page indicates which trellis designs should be used for a quince espalier. Choose a trellis in the heavy or massive wire rope ranges; for smaller espaliers you can also use a medium or easy basic trellis. Quince can also be grown on wooden trellises. The climbing aid needs to be strong enough for the tree once it has grown to size. The main axes of the trellis should be about 60 cm apart. Any distance to the wall can be chosen. More details under "shaped trees."