You can make up a small container of 1 part hydrogen peroxide 3% to 4 or 5 parts water and soak the plant in it for 20-30 minutes before planting. I also often rinse pond plants off well under tap water before soaking. You don't need to rinse them after the peroxide soak.
Also be aware if the plant was growing with just roots in the water it may or may not be fully aquatic. If it is fully aquatic the leaves will change from emersed growth to immersed growth. Also be aware you may or may not have enough lighting for plants grown outdoors in ponds.