Red annuals for window box...

I'm not a real expert on trailing/vining varieties, and my sister-in-law has asked for my advice. Can I in turn ask you all? She's looking for a red trailing flower that will give the desired "spill-over" look for full sun windowboxes this spring/summer. Any ideas? I've thought about some petunia, the red morning glory varieties, maybe nasturtium?. Zone 7a/6b; full sun. I do appreciate it.

million bells
fushia
lobelia- trailing types- but Im; not sure if there is a red

Zeppy,

Verbenas like sun and there is a red one. Not too trailing, but it will hang a bit and they love sun. The trailing Verbena is blue, at least from what I have seen....

Therer are also hanging Geraniums. Remember, that plants in window boxes have to tolerate crowded conditions and will need extra watering as they dry out qyickly. Feed them often.