This will take you through how to plant a bare-root tree sapling, which should ideally be done in spring or early autumn, to give the tree's root system time to establish itself before drought or frost hits.
If you're going to plant a lot of trees, I recommend investing in a dibble tree-planting tool. If you're just doing a couple or a handful, using a hand trowel (aka small shovel) will work just fine! I also have step-by-step photos of this process below these instructions, too, so feel free to peek at them for guidance :)
Do some basic research on the variety of tree you're planting, and choose a planting site that fits the requirements of your tree (aka full sun, or partial shade, etc). Spending 5 minutes to choose the right planting site greatly increases the long-term health of your tree.
Dig up some soil in the general area where you will be planting the tree. We will refer to this as 'native soil'. In a bucket, mix together 3 parts native soil with 1 part compost. Set it aside.
If you have a hand trowel, dig a hole that's about 4 inches in diameter and deep enough so that the tree's roots don't touch the bottom.
If you have a dibble, insert it into the ground at a 60-degree angle up until the hilt of the dibble. Push it forward to a 90-degree angle to create your hole, then remove the dibble. Make sure your hole is deep enough so that the tree's roots don't touch the bottom.
Hold the tree by the stem over the center of the hole, and make sure the area with roots is *just* below the soil line around it. You don't want any roots above the soil line, otherwise the tree will dry out. You also don't want any branches below the soil line, otherwise the tree could rot.
Now look at the bottom of the hole. If the root are dangling straight down into the hole, that's great. If the roots are touching the bottom of the hole, or caught on the side of the hole and forming a 'J' shape, take the tree out and deepen or widen the hole as-needed, and dangle the tree in the hole again until the roots hang straight down and don't get caught on the sides.
While holding the tree in place (still making sure the roots are *just* below the soil line) with one hand, use the other to start filling in the hole with the native soil and compost mixture.
Fill until the soil in the hole is level with the surrounding soil line. Pat the soil gently around the tree with the flats of your palms. If it sinks a bit, sprinkle some more native soil and compost mixture around the tree to make its level even with the surrounding soil line again.
Use more of the native soil and compost mixture to make a 1-inch high mounded circular border around the tree, about 3 inches away from the base of the tree. This will help the water stay around the tree when you water it, rather than just flowing away.
Water the tree with your watering can. Wait a few seconds for the water to drain, then water it again. Repeat one more time.
Sprinkle a a 1-inch thick layer of mulch around the base of the tree, going out 4 to 6 inches in diameter around the tree.
Use your pointer finger to nudge any mulch that's touching the tree's stem about 1 cm away. Ideally, you don't want a lot of mulch actually physically touching the tree because that can cause fungal rot, but you do want a good amount of mulch around the tree.
Now that the mulch is there, water it one more time. And that's it! You've successfully planted a tree!
Every tree has different hardiness levels, so do some research on the variety you're planting and follow the watering guidelines for that variety.