must be borne in mind that, apart from some 'Duke' cherries, which
are a cross between sour and sweet cherries, none of the dessert
(sweet) varieties are fully self-fertile and a single cherry tree
is unlikely to set fruit without another nearby. As with other
fruit, pollinators have to flower at the same time. Also, some
cherries are incompatible pollinators with others, quite apart
from flowering time. Cherries fall into groups of mutually incompatible
pollinators, but the collection of data is very incomplete. The
situation is partly helped by a few cherries being universal pollinators,
pollinating any other cherry that flowers at the same time. Otherwise,
one has to select pollinators which are known to be in another
incompatibility group, and which also flower at a similar time.
It is confusing but we give a guide to suitable pollinators below.
Avoid the same incompatability group and choose from the same
or adjacent flowering time. Use a universal pollinator if needed.
Cherries are grafted onto Colt (semi-dwarf) rootstocks, or equivalents
like Pi-Ku, or dwarfing Gisela 5. Colt can still give quite large
trees – up to 20ft – if unpruned.