To name some varieties suitable for Colorado. Bring in several different types of apples, preferably ones grown here in Colorado. Provide the students with fruit tree catalogs to look through. Dwarfing rootstocks are generally used for apple trees. There are many excellent apple rootstocks to choose from because of extensive research done since the early 1900's at the East Malling Research Station in England.
Pear trees are dwarfed with quince rootstock, which is an entirely different genus.
Dwarfed pear is often short lived. Peach and apricot dwarfing has not been commercially successful. There is a need for more research and development of dwarfing rootstocks for most trees, other than apple. The use of rootstocks to dwarf peaches and apricots has not been as well researched and developed as apples. Genetic dwarfs can be obtained from plant breeders.