Green where you live.
Whether you have a yard, forty acres or a fourth-floor balcony, there's a tree you can get in the ground this season, and usually someone who will help pay for it. Start with where you are.
Or use my location (we think you're around Columbus, OH).
I have a yard
One well-placed tree does more for a house than most renovations: shade in summer, a windbreak in winter, and something to look at for fifty years.
Pick the spot before the tree.
Look up for power lines and out for the mature spread, not the sapling. Large shade trees belong 4.5 m (15 ft) or more from foundations and walls; small flowering trees can sit closer. In the US, call 811 before you dig; it's free and it's the law.
Pick the tree for the spot.
Native and locally recommended species take less water and shrug off local pests. The tree directory below shows what's native, what does well, and what to avoid where you live.
Get it free or cheap.
Many cities, utilities and nonprofits hand out free or discounted trees to residents each planting season. Street-tree request lines plant on the public strip at no cost. The programs for your area are listed below.
Plant in the dormant season, then water like you mean it.
Fall through early spring in most climates. Dig the hole wide, not deep; keep the root flare at grade; mulch a wide ring, not a volcano against the trunk. Water deeply once or twice a week through the first two summers. Don't top it, ever.
I manage land
Acreage changes the question from which tree to which forest. Most places have a government forester who will walk the land with you for free.
Start with the goal.
Timber, wildlife, shade for livestock, erosion control, carbon, or just a woodland to leave behind: each points to different species, spacing and help.
Ask the state or provincial forestry agency first.
In most of the US a state forester provides a free site visit and a stewardship plan. Equivalent services exist in Canada's provinces, the UK nations, Ireland and Australia's states.
Use the cost-share.
Federal and state programs pay a share of planting and fencing: in the US, USDA's EQIP and the Conservation Reserve Program; in the UK, the woodland creation offers; in Ireland, the afforestation schemes. Deadlines are annual and paperwork is real; the programs below link to the current rules.
Buy seedlings by the hundred.
State nurseries and conservation districts sell bare-root natives cheaply in winter. Plant mixed species, protect from deer and drought the first years, and keep records: you'll want them for certification and for the next owner.
I rent, or live in an apartment
You don't need a yard to change the block. Most of the trees on a city street were asked for by someone who lived in an apartment nearby.
Request a street tree.
Many cities plant on the public strip at no cost, and renters can ask. Look for a 311 line or 'request a tree' page; they're in the list below where we have them.
Adopt the one that's already there.
Young street trees die of thirst, not age. Many cities and tree groups give watering kits and ask residents to take a tree. Twenty gallons a week in summer is the whole job.
Show up to a planting.
Volunteer days are the fastest way to put trees in the ground without owning any of it. The events page lists the ones near you with links to register.
Grow one on the balcony, and ask about the grounds.
Dwarf fruit trees, olives, figs or a Japanese maple live happily in a 60-litre (16-gallon) pot with sun and water. Building owners, HOAs, schools and congregations own a lot of lawn; most say yes when someone offers to organize the planting and the care.