So oaks are great in the Midwest. You could try collecting acorns from nearby trees in the fall and tossing them over a fence to see if they grow.

However, if you live in a naturally forested area, it’s often more important to remove invasive species and prevent people from killing young trees than to plant new ones. If you see a lot or park that seems promising, see if you can connect with the manager of the space to see if they would allow you to clear out some weeds and give baby trees space to grow. You’ll need to learn to recognize the desirable and undesirable species to do this.

In more manicured, urban spaces, it’s often necessary to plant larger trees since smaller ones will simply get mowed over. Sometimes there are local orgs that give them away for free, or you can collect seeds and put them in pots to grow them out, though that does take an extra level of knowledge to do correctly.