Question
I am anxious to find information on which plants grow well in window boxes. I have 3 very nice vinyl boxes in front of my house- they range from full sun to some shade. I prefer to plant pink, white and blue/purple shades and would like the plants to cascade over the boxes. Any information you could supply would be greatly appreciated. Thank you, E

Answer
Blue is the least common color for cascading annuals. I would not use perennials, if you want them to put on a long summer show. Perennials don't bloom long enough for a long colorful display.
Here is my list of favorites, all cascading:
Petunia (Wave, cascadia, superfina)
Million bells (best flowering) Also known as Calibrachoa
Bacopa (Small flowers)
Alyssum  (Small flowers)
Lobelia (blue)
Verbena (trailing) (Purple)
These flowers can take some afternoon shade, but will bloom much better with full sun.

Flowering may be more sparse when the summer temperatures are very high, but they will bounce back when it cools again. Do not fertilize when it is hot. The plants are in a heat dormancy, and can be harmed by the fertilizer.
Keep water on them, but don't let them drown. They will dry twice as fast in a window box, so check them every day. If it is hot, you may need to water twice a day. Be careful to put the water on the soil, not the flowers.
Use a good potting mix, with nutrients, and moisture retention in it, and good drainage.
Give the plants room to spread. Don't over crowd them or they will remain small and cramped.
I like to pick two or three large spreading plants and fill in the space between them with smaller less spreading plants.