Sounds like allium, ornamental onions. The best way to buy them is as bulbs, in the fall. Aren't they fun? Here is a link that might be useful: Allium images

Token has it right, common names are evening primrose and nine o clocks. You can watch these flowers open, right before your eyes, as they open very quickly & sometimes they will even shake a bit-we always watched them as children & I still enjoy doing so. They get lanky & weedy looking but I always let some reseed to watch open & show others. Look for the fattest bud in the early evening, then check about dusk & you will soon have their schedule. Mine opened about 8:45 pm last night. The blooms close during the day but will linger if it is overcast or rainy. Susan

There's a lot of plants that look like this. If flowers have not been seen it may not be possible to tell what this is.

Thank you for the closer and clearer images - that makes the difference.