They are too different species and M. didyma is red. I have seen M. fistulosa in shades from almost white to purple. I have actually not seen any pink ones.

If you get M. didyma 'Jacob Cline', it will be very red and have better mildew resistance than the species.

All of them are fairly aggressive about spreading when they are happy.

Monarda fistulosa is the native plant around here. It doesn't look like M. didyma covers much of IL at all, according to the USDA map. I prefer red too, however, I've never seen M. didyma at native nurseries I have to drive to, so I went with M. fistulosa. I'm not much of a pink person either (why are we females supposed to love pink?). When in bloom with prairie and meadow Liatris, Monarda fistulosa is really quite beautiful, IMO. I guess it's a matter of opinion and how native to your area do you want to be. Beggars can't be too choosy here, I have to drive hours to find a native nursery or order on-line.

There are cultivars (hybrids? I never could get that straight!) of M. didyma if your wife is set on red. 'Jacob Cline' is one I keep hearing about.

A hybrid is a cross between two species and is correctly noted with an "X" in the name:

Ilex x attenuata 'Savannah' is a cross between Ilex opaca and Ilex cassine, for example. A hybrid can be a cultivar - that is to say a "cultivated variety" - once a good form has been identified and named. In the case of Ilex x attenuata, several cultivars have been named from the many crosses and are in production.

But you can also have a straight species cultivar which is represented by using the whole name: Monarda didyma 'Jacob Cline'. In that case it is thought that the form is a natural sport of the species itself, not a hybrid cross between species. For example you might sow a lot of seed and one particularly beautiful, colorful or mildew resistant individual comes up and you select and name it.

Either way, once the selection is made and named, vegetative propagation keeps the cultivar consistent for nursery production.

At least that is my understanding!

thank you everyone for your help.

esh, come back! I know I've heard that a cultivar is a "cultivated variety". I thought a straight species was a straight species, not a cultivar, not a variety, no hybrid, nothing, just the straight species. I never understood what they called the other plant that they thought was a "child" from the straight species. Makes me want to pull my hair out trying to understand it all!! Since I like my hair, see why I don't understand it all Paul?