My favorites are snapdragons, calendula, and dwarf morning glories. Dusty miller grows wonderfully in my garden and looks great in fall and Christmas flower arrangements. If there is not many swelling buds, the tree may have some winter kill. When planting a tree or shrub, dig a hole twice as wide as the root ball but only as deep as the ball which should rest on a solid soil foundation. Experts now recommend that you not add soil amendments to the planting hole because a richly amended planting hole will act as a sort of container.
Plant roots have a hard time adapting to the native soil outside of an amended planting hole.
Remove the pot or if it's wrapped in burlap remove any wire and plant. Finish filling the hole with soil and then water again. Make a mound of soil in a ring around the tree to act as a reservoir and water one more time. Try to keep the soil around the tree moist throughout its first season to help it get established. I have to add to that as my personal fav, the variegated weigelia.