I planted an Italian plum tree 5 years ago. It is now around 12 ft tall and flowers every year but bears no fruit. I think I need another plum tree to pollinate it, but do not know the variety. I do not want to graft unless you suggest I do so. I live in southern Ontario.
The European or Italian plum tree (Prunus domestica) should start to produce fruit 3-5 years after planting, although sometimes this may take longer. There are many varieties of the European plum tree. Most varieties are fully self-fertile (i.e., their own pollen fertilizes their flowers) or partially so (i.e., under the right conditions, they can self-pollinate), so do not need a pollination partner. However, an appropriate partner located nearby can encourage the plum tree to produce more and better fruit.
I suggest that you wait another year or two to see if the tree sets fruit. We’ve had challenging weather over the last two or three years – tree blossoms need to be pollinated, and late frosts can damage blossoms, preventing this. Also, if there is a frost just after pollination has occurred, the initial stages of fruit formation can be damaged.
If the tree does not fruit, then it may need a “pollination partner”. The pollination partner must be a different variety of European plum. It is important to consider that European plums can pollinate other European plum varieties, but do not cross-pollinate with Japanese plums (Prunus salicina) or American plums (Prunus nigra, Prunus americana)
The partner tree should be planted 12-18 feet from your tree. As well, the two varieties must have the same bloom times, so that the wind and insects can transfer pollen from the flower of one tree to that of the other. This is not usually a concern with European plum trees, as most varieties flower at around the same time, with good overlap for effective cross-pollination. If you do need another tree, speak with someone at your local garden centre to help select a different variety from your own.
As you suggest, another way of encouraging your tree to bloom is to graft a branch from a different European plum variety onto the tree. I’d suggest leaving this option for last. If you don’t want to plant another tree, when your tree is in bloom, find a compatible European plum variety (also in bloom) and cut a branch from that tree (you may have to scour nearby neighbourhoods, or ask your local garden centre if they can help). Put the branch in a container of water at the base of your tree. Bees should transfer the pollen to your tree.
As well, your tree may be putting a lot of energy into making leaves, so remember to prune the tree once a year, in early spring or late winter, to remove unwanted growth. This will also maximize fruit-bearing surface and permit sunlight and air to circulate through the branches. Bear in mind that flowers bloom on wood that is at least one year old, so proper pruning technique is essential. And once the tree starts to fruit, feed it with 10-10-10 fertilizer in early spring.