Answer: Full sun all day or direct sun all afternoon are challenging hot and sunny locations for a window box. Morning sun is not quite as stressful, but would also require plants that like full sun. The deeper and wider the boxes the better as this allows for more root space and helps the soil stay moister longer. The type of soil is important in that it helps hold water and air for the roots. Use a soilless potting mix formulated for container plants and consider using a water holding polymer mixed into the soil to help reduce water stress. (Some potting mixes have it already added.) Some plants that work well would include marigolds, million bells (Callibrachoa), Wave petunias, dusty miller, annual salvias, sun coleus, the so-called spikes (actually a draceana), geraniums, lantana, and thunbergia (black-eyed Susie vine). Your local nursery staff may have additional suggestions. If you can use a trailing plant to help shade the south and/or west side of the box that can help. Make sure to water enough that the soil stays evenly moist (not sopping wet and never dried out.) I hope this helps!
Q&A Library Searching Tips