Crabapple trees grow best in full sun, but tolerate light shade. They prefer soil on the loamy side, but are comfortable with most soil conditions (even clay) as long as the soil is well drained. It should be on the acid side (pH 6.0 to 6.5). Avoid planting crabapple trees in a "frost pocket," where cold air flowing downhill collects behind large obstructions such as hedges or a low spot in the ground or where they will be exposed to excessive wind. This helps prevent winter damage. Make sure the site is well drained.
Stake a newly planted crabapple if there is any chance of its being blown over or uprooted before it becomes established. Sink three sturdy supporting stakes in the soil about two feet outside the dripline, equidistant from the tree trunk and each other. Loop cables wrapped with rubberized protection or soft clothesline material around the trunk and fasten each of them to a stake. Keep the cables a bit lax so the tree stem has a little leeway to move so it will grow strong. Check often to make sure the cables are not binding or injuring the trunk in any way. Remove the staking once the roots are securely anchored, in about 6 months. For more information see Planting A Tree