Four O' Clocks, but some consider it invasive. They have a very nice fragrance, I like them and have them. My Zinnias stay open all the time, so do the roses, the Cosmos... Almost everything in the garden, what kind of flowers do you have? I can only think of 3 that aren't in bloom in the late afternoon, the Mexican Petunias (invasive), Daylillies, Morning Glories.

Datura for evening/night opening....usually not open till twilight.

I do have Mexican Petunias, they came w/ the house and I do like them. we bought the house last july and in the year the Mex Petunias have not "gone" anywhere, they have gotten leggy ( i think that is the term) but I did not cut them down during the fall/winter and right now I just love that they have flowers every day so I cant bare to prune them now, but I will once I notice less flowers!

I have Blue daze and they seem to close at night - well I think they "die" I think the flower is a 1 flower a day type thing and maybe the same about the Mex-P.

I have two Gaura (light and dark pink) but they seems to stay open, but they are small so I think when I look at the space I notice the closed looking flowers more then them (but I love them - hope they continue to grow and attract butterflies - I have a black mothy butterfly that hangs out in the Gaura).

I have a cucumber plant that has flung it's self out of it's lil pot, I fear I should not let it hang out w/ the other flowers, but it too have lil yellow flowers, so I have not moved it. It was just something my son did w/ the neighbor kids, we did not think the seeds would grow or that it would still be alive. I dont think it will stay, but I have not moved it (not sure what I should even do with it)

I have Aloe that is in bloom. I was thinking of moving them in the future, but now that they have bloomed (they did not do that last year when we 1st got the house) I think I will keep them there a little longer.

It is just a small space that only had the Mex - P and the Aloe, so I added the Daze and the Gaura just based on looks and price. I am slowly adding more things in and that is when I thought I should make a conscious effort to find something that likes the evening so I have pretties to say hello to when I get home.

in the front yard I am doing a tropical thing, so they are open all day/night, but in the back I want a lil flower/butterfly area.

Sweetmonkeycheese (gee, that feels a bit familiar to call you!): I sympathize with you.

You've probably done this already: visit a nursery after 6pm (usually a big box store) and see what is still open.

In my yard (I have both sun and shade), the best butterfly attractors blooming 24/24 all summer, are 2 woody stemmed bushes: fire bush (Hamelia patens) (orange/red flowers) and jatropa (red flowers).

Also awake are vines: bleeding heart (white & red, and pink /red/purple; passion flower (a purple and a red); and on the ground: beach daisy (yellow). Butterflys on and off.

Not BF attractors for me, but blooming 24/24 all summer:
Begonias (red, pink/white) - and their leaves are green on top and red beneath, so sun shining through can make for more color.
Pentas (pink and red)
Red salvia
Periwinkle (pink)
Sunshine mimosa (red powderpuffs).
Shrimp plant (red) (also comes in yellow).
Hibiscus (peach).
Crepe myrtle (pink; lavender)
Epidendrum radicans orchid (orange/yellow)
And...
Caladium (red&green leaves)
Orchids (blooming is sporadic).
Crotons (can be colorful, of course, but no blooms)

I hope this is helpful.
Irma