Answer: It is difficult to grow hardy plants year round in this type of situation. A raised bed tends to dry out quickly and it is also subject to the freeze-thaw of oscillating temperatures during the colder months. Since the roots are not as well insulated as they would be in the ground, it is very stressful on the plants. Add to that the reflected heat from the stone patio and you have a very difficult spot. Generally speaking viburnums prefer an evenly moist organic and humusy root area so I do not think they would be such a good choice. The weigela is a possibility and is in my experience a much tougher and sturdier plant, however it is not very attractive in the winter time because the branches are coarse, it also leafs out very late in the season each spring. To some extent the best choice will depend on the size of the container/planting box, but you might like the new dark foliage elderberries such as Sambucus nigra "Black Lace" for a dramatic effect. Another option might be to plant something tropical there such as cannas or elephant ear or a purple fountain grass. The first two can be dug each fall and saved from year to year, they all like heat and sun and need a rich, moist soil. Another possibility might be to use a water feature there instead of a plant. I hope this gives you some ideas. Your local professional nursery staff may have additional suggestions based on a more detailed understanding of the planting area and your design goals.
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