it all depends on the weather. If you do it at the wrong time of the year it won't take. Every species has different requirements. Avocados for example, need to be grafted just as they're putting out new growth in spring or autumn and the new graft needs to be protected from direct sun. Olives are best grafted in the winter.

Plants of the same botanical genus and species can usually be grafted, some species are harder than others. Citrus can be grafted onto any citrus, and you can graft ten different types of citrus onto a single tree if you want. For example, you could use Bitter Orange or Rough Lemon as the root stock and then graft a variety of grapefruit, orange, lemon, clementine, lime all on the same base.

You can graft plums, apricots, almonds, nectarines, cherries and peaches on the same root stock since they're all related.

Quince is a common base for pears, loquat, hawthorne, choke berry, mountain ash, juneberry, german medlar. While apples can be grafted onto crabapple to control their growth. Some apple varieties can also be grafted to quince.

Some cultivars need an intergraft to succeed, so if you graft a compatible pear (like Doyenne Du Comice) onto quince as an intergraft, you can then graft any pear variety onto that. For apples, the recommended intergraft to quince is the "Winter Banana" variety of apple, then any apple can be grafted to that.