What size gaps are you talking about? And are you looking for perennials or annuals? What Zone are you in?

the gaps are a about a foot but there are several of them. Iam looking for perennials and i am in zone 6. As i mentioned earlier iam looking for something that spreads and attracts hummers.

greenthumb

Of ones I can think of that are perennial , spread and attract hummers are bee balm[the taller kind] and cardinal flower. Something else you might keep in mind that you could do with annuals that I did and it works. Another forum member had mentioned after a couple of frosts cut the annuals down to about 6 inches or less and cover the entire bed with a tarp or I used plastic[visqueen] and cover the edges with whatever bags of mulch, sheperds hooks , heavy rocks anything to seal the edges. Then dont uncover till it warms up april/may. Before I tried this method I had not had agastache tutti frutti come back for me here [tender perennial] but this year it did after covering. Also all the black and blues plus the new ones formed by the runners,, hope this helps.

Bee balm is a must have; Jacob Cline is gorgeous. It's not as aggressive as some people have complained about; I truly wish it were. Mine seem to be dying off and I've been on the hunt for new plants. I see them everywhere, but now that I need one or two, none of my local nurseries have them! I have also noticed plenty of activity on my Lychnis chalcedonica (Maltese Cross). I have 3 varieties and this is the first year they've been hitting it alot. They do tend to reseed, which isn't a problem for me (I love it), but is easity managable by removing the spent seed heads.