YOu will find small trees at most nurseries. There are so many...
Spme trees can be started with a stick...lile the Cuban Acacias, just stick a piece in the ground and it will grow.
Or you can grow your own avocado tree, if you have deep soil...google it to see how to sprout it.
You can grow your own coconut tree if you leave a coconut on the ground and dampen it regularly...
Mahogany will grow from seeds and they have pods with hundreds of seeds...
Where do you live? Since it is better to get a plant that is right for your area of the woods...not some import...
Some trees can become a bother...like laurels, almond or Norfork Pines...
HB