Seems to me that you're making the (false) assumption that
gardeners can't be conservative.

That's a peculiar conclusion. It seems like an advisory statement to me.
"This is what I heard. If it bothers you then consider shopping
elsewhere"
It didn't preclude the possibility that someone would be conservative.

Being one of those mean rich conservatives myself, I'd be more inclined to
shop at HD if I really believed the initial premise that HD supports the
Republican party. However, most big businesses butter both sides of the
bread to help ensure their future regardless of who is in power; big bucks
from HD have probably made it into the hands of the Dems too, it just may be
hard to trace. I'm fairly confident Lowes does this too (no facts, just
presumption on my part).

If one wishes to choose a store based on reasons other than price, quality,
and selection of merchandise at each store (since the box stores are pretty
similar in most aspects), I'd suggest a more positive approach. Reward the
stores that help your community the most, and be very vocal about it so the
store managers know why you're shopping there.

For example, although Wal-Mart has become a China-product outlet mall, the
stores usually really make an effort to improve the communities they're in
(I know, blanket statement that will have plenty of bad examples; but there
are still plenty of parks and playgrounds that wouldn't exist if it weren't
for organized Wal-Mart employees volunteering and putting out a lot of hard
work). I know Lowes has received many non-monetary honorary awards for
their hiring practices. Although Lowes doesn't have an official policy of
hiring the disabled or handicapped, it seems they're far more likely than
most businesses to hire those people who are often discriminated against
elsewhere. I like that, so I lean toward shopping at Lowes, because I think
they're doing the right thing by helping those who have a hard time getting
hired anywhere. Lowes managers have said it's strictly good business on
their part (less employee turnover saves bundles on training losses, happier
stores bring return customers, etc.), but I say good on 'em for a history of
good hiring moves and being decent human beings. Plus, unlike other
companies that hire the disabled but then keep them hidden from the
customers like they're hiding a disease, Lowes just mixes the disabled in
with everyone else and doesn't try to hide them--they're just regular
employees like everyone else. To some people with mental disabilities the
whole concept of being treated the same as everyone else, being considered
just an average American by others, can often seem beyond their reach; but
Lowes has repeatedly proven it's not. (Search for the DC Melwood clinic
article about Lowes if you doubt my words).

So from this crusty, mean-spirited, rich, grouchy, middle-aged male
capitalist pig (never wore Birkenstocks in my life, probably never will;
only hug a tree when I'm climbing into my deer stand; go ahead and
stereotype me as you will), thank you Lowes and Wal-Marts of the world for
trying to do the right thing while still making a buck and surviving the
capitalist marketplace.