Hi, again. Thought I would come back & share what I tried. A recipe
I hadn't found online but which several people in town suggested, was
a 50/50 mix of borax & icing sugar. Since I read that carpenter ants
don't eat solid food, I put a little water in it to make a syrup, put
a teaspoon or 2 in some little yogurt containers with holes poked
around the sides & set them near the nests I found in a concerted
hunt. I "painted" a bit from the sides to the bottom to give them a
scent trail, & covered the tops with tinfoil to keep out rain. The
ants were into it quite rapidly.
Also used some of the "Ant-B-Gon" drops, in the little red bottle. It
has a guarantee, yet!! to eliminate the colony with just a few drops.
Very skeptical... but having found an entry point in the kitchen
cupboard, I put a little puddle of the stuff on a piece of tinfoil, &
within 20 minutes there were up to 20 ants all around it like zebras
at a waterhole. They had a binge for an hour or so. We have not seen
any in the kitchen since. Outside, there is much less activity in the
colonies I found. With a 2nd round of yogurt-pot traps I made the
syrup with the Ant-B-Gon drops, & the one trap in particular was
completely full of them in no time. I think it takes a couple of
refreshings of the traps before you get them all, but they do appear
to take the bait. Not sure how well it works if you don't put it
right at the nest -- it might kill the ants too quickly for them to
take any back to the nest.
There is a new(?) Raid product which is an outdoor nest-eliminator...
a spray can with a long tube that you stick down the holes; it sprays
foam into the nest. This appeared to work very well on another nest,
before I got into the borax.
And, having found some suspicious places where they might be getting
into the bedroom around the baseboard, I spent rather a lot of time
blowing cream of tartar into the crevices with a straw. Supposedly
they won't cross it. Haven't seen any there either.
I think the lull (?) in our invasion is the result of a combination of
all these things.
Not sure why the other person who posted recently hasn't had success
with the borax in the greenhouse, but if you haven't tried preparing
the stuff this way, you might want to try some of the above before you
get into toxic spray stuff.
Hope that will help someone with future ant problems.

Alison