Answer: Magnolias have lots of surface roots and you won't want to dig into them or damage them in any way. Start by moving the mulch out of the way and then carefully digging down with a hand shovel. If the area is reasonably root-free, you can plant in that spot. I'd explore all the areas you wish to plant before purchasing plants so you'll know how many holes you can fill with new plants. Once you've chosen your plants, you can plant them in the native soil (no need to purchase top soil or potting soil). After everything is planted, water each of your new plants in well and then replace the mulch.
Best wishes with your new flowers!
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