Keeping fruit trees small through pruning can make them easier to manage, increase their yield, and make harvesting easier. Here is a guide on how to prune fruit trees to keep them small.

1. Choose the Right Trees: When selecting fruit trees for a small space, look for dwarf or semi-dwarf varieties. These trees are naturally smaller and require less pruning to keep them manageable.

2. Prune for Shape: When pruning a young fruit tree, begin by removing any broken, diseased, or crossing branches. Then, choose the main branches that will form the tree's structure and prune back any competing branches. Train these branches to grow in a spreading, open shape to allow sunlight to reach all parts of the tree.

3. Renewal Pruning: Every year, remove about 20% of the tree's oldest branches. This will encourage new growth and keep the tree small and manageable. Cut these branches back to the trunk or a main branch.

4. Summer Pruning: In the summer, when the tree is actively growing, remove any water sprouts or vertical branches that are growing too vigorously. These branches do not produce fruit and can shade out the productive parts of the tree.

5. Thinning: Thin out the fruit on the tree to reduce the weight on branches and avoid breaking them. Remove any fruit that is small, damaged or diseased. This will also allow the remaining fruit to mature and ripen properly.

6. Prune Annually: Prune your fruit trees annually to maintain their size and shape. Regular pruning will ensure that your tree stays healthy and productive.

7. Keep Tools Sharp: Make sure your pruning tools are sharp to make clean cuts and avoid damaging the tree. Use bypass pruners or a saw for larger branches.

Pruning fruit trees to keep them small requires regular maintenance and attention. By following these steps, you can keep your fruit tree healthy and productive, while making it easier to manage in a small space.