Lobelia
On a walk to find butterflies, I found this flower:
If I’m right, it’s Blue Lobelia or Great Lobelia (Lobelia siphilitica). It that’s right, it’s a pretty good find, Lobelia siphilitica is a rare species in Massachusetts, but it may be common elsewhere.
Nature Diary 
That’s a good companion to its genus mate, the cardinal flower.
I know of only one location nearby for cardinal flower, I’d love to see one again. I should go visit the spot.
A few days ago I went to check out a place that had lots of cardinal flowers at this time last year. Unfortunately not a single one was there this year. I hope you have better luck when you visit your spot.
This species is listed as “present but rare” here — in two counties! We do have a couple of pretty versions; my favorite might be the L. puberula, especially when it turns up in a dark purple. The stripes on these buds are especially interesting; I don’t think I’ve seen those before. It’s interesting that they seem to begin as white buds and then darken. Is that a usual feature?
This is a new flower to me, I don’t know its habits yet. I made an ID query about this photograph, but they respondent wants more information. Alas, I didn’t photograph the foliage. Hope it’s still blooming when I go back!
I just checked my files, and my best photos of Lobelia were taken in east Texas in — November! Even adjusting for latitude, it seems possible to me that yours will linger for a while.
So nice ! Lovely color.
It was such a nice discovery – right in the spot where the expected to find a rare butterfly.