Can you graft different types of trees together?

Orange trees are usually grafted onto lemon trees. Lemon trees are hardier.

I’m not sure how it works with different trees, but my grandfather grafted a pear branch into a large blackcurrant (or something similar) bush.

They have to be related to each other to a certain degree, as in being in the same botanical family. Citrus can be grafted on citrus, and you can even graft more than one type of citrus onto a particular root stock. For example, you might use Rough Lemon as the root stock and then graft a variety of grapefruit, an orange and a lemon all on the same base. The result is called a “Fruit Cocktail tree.”

You can graft plums, apricots, almonds, nectarines, and peaches on the same root stock, or you can graft different varieties of the same fruit on one root stock, in order to get fruit over a longer time period. Pears can be grafted onto quince to produce a dwarf pear tree, and apples can be grafted onto Crab apple to produce a dwarf apple tree, if you have a small yard but want fruit trees.

To summarize:

“Plants of the same botanical genus and species can usually be grafted even though they are a different variety. Plants with the same genus but of a different species often can be grafted. But the result may be weak or short-lived, or they may not unite at all.

Plants of different genera are less successfully grafted, although there are some cases where this is possible. For example, quince, genus Cydonia, may be used as a dwarfing rootstock for pear, genus Pyrus.

Plants of different families cannot be grafted successfully. Although it has been reported that relatively short-lived grafts of herbaceous plants of different families have been made, there is no successful practice for commercial or home grafting of woody plants of different families.”

Just don’t graft tomatoes onto their relative jimson weed or the result is a bevy of poisonous fruit!