Answer: It's really difficult to diagnose a plant problem without seeing it, but I'll try. Trees and shrubs can go through an adjustment period right after they're planted. They can look pathetic for a few weeks until the roots become established in their new home. It's important to water regularly (one-inch of water per week) during this adjustment period. Sometimes it's easiest to water if you build a water basin or water well beneath a newly planted tree by mounding up soil to create a large basin. Fill the basin with water, allow it to drain, then fill it a second time. This method of watering will ensure that the moisture is concentrated over the root mass and will trickle down and wet the entire root mass. At this point I'd simply water regularly (once each week) to encourage good root establishment. By next spring the roots should be all settled in and you should see some new growth.
Best wishes with your magnolia!
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