https://www.chrisbowers.co.uk/guides/cherry-trees.php Quote:Colt Rootstock
Colt has been fully tested in this country and has been proved ideal for a wide range of soil types previously too difficult for cherries. Fully establish 8 year old trees have been controlled to 12ft height, and this can be lower with pruning technique. The weight of the fruit and protection netting brings the branches down even lower, and allows picking from the ground. No ladders are needed. Trees on Colt rootstock fruit very early in life, often the first year after planting, and are in full fruit by the 3rd year. In our trials, cherries on Colt have proved far less susceptible to bacterial canker.
and
Quote:On Colt rootstock these can now be grown as a traditional fan against a 6 or 8' wall, or in the open as a pyramid, where the height can be restricted to about 9' with easy pruning. Both of these ways of pruning are very easy to net against birds. For fans and bush, the trees should be planted 15' apart and, for pyramid training in the open garden 12' apart.
Sounds good, bending the branches, no need for a ladder to pick, easy to net with height controlled easy enough. Colt also tolerates clay OK.
Another source says 2.5m (8') spacing apart.