Buy your Wych Elm tree. Make sure it does not have any blemishes on the bark of the trunk. Keep it well watered until you are ready to plant it. Typically, these are available for planting in the early spring, but before it has started budding. Otherwise, you can plant it in the fall a few weeks before any deep freezes.
Locate a site for the tree where it will have good rich soil with good drainage and plenty of sun. It will grow into a rather large shade tree with beautiful ridged leaves. It will not tolerate soggy wet soil.
Dig a hole that is bigger than the root ball or plant pot it came in from the nursery by about at least 6 inches in all directions, which would actually be 12 inches bigger than the ball or pot. Set the dirt on a tarp beside the hole so you can use it to refill the hole.
Throw a few shovelfuls of compost into the hole and mix it with a little dirt. Remove the tree from the packaging it came in from the nursery and set it into the prepared hole. Hold it straight up and fill the dirt in around it. Tamp it with the heel of your boot as you go until the hole is all filled and the dirt has been built up about 6 inches above the soil line.
Water the tree well for the next several weeks, making sure the soil does not dry out. Of course, if it is raining, there is no need to water. Water the area around the tree about 3 feet out in a radius from the trunk of the tree.
Clip some twigs in the spring when the buds are swollen to use in your decorations. Keep them dry and you can paint them with a little fingernail polish for a little more pop in the color and to prevent them from further budding.