I tried coreopsis 'Star Cluster' last year. It is among the "Big Bang" series, but this one is much shorter than 'Redshift' (which I also have). The 'Star Cluster' plants were tiny last year, but bloomed all summer long (zone 7b) until frost. The height was just under 2 feet and it is hardy to zone 5. This year, the foliage tripled in width! These plants are the hardiest coreopsis that I've seen. Mine are planted in good soil in my cottage garden, but didn't flop last year. The yellow is pale, not gold and it develops the burgundy "eye" as the weather cools. I have that first grouping planted with salvia 'Victoria Blue' and echinacea 'Pow Wow Wild Berry'. I added another grouping with eucomis 'Sparkling Burgundy' to echo the eye color and that group is backed by penstemon 'Husker's Red' with more echinacea to one side that is backed by monarda 'Raspberry Wine'. Cameron

I went out to look at mine, and it is clearly a montauk. Older books called it a nippon daisy. I saw one early in the season at a Farmer's market that was also mislabled as a shasta. The grower had grown it from seed sold to him as Shasta Daisy. Mislabled seed could be the source of the error.

I'm not familiar w/ the Marguerite, but I have a patch of Blackfoot Daisies that comes back every year. And every year is lovelier than the last! It does self-seed, but very slowly so not invasive. I have mine out in the H*** Strip where the concrete all around keeps it nice and toasty. I do water it everyday when it gets REAL hot, but otherwise don't do anything but cut it back a bit in the fall. It is blooming now and will bloom til Fall. I personally love this plant and get lots of compliments on it! I started out with two or three 4" pots and it is now a nice mound of white daisies! I'll post a photo later, can't find them now.

If the foliage looks "exactly" like that of shasta daisy, then chances are quite good it IS a shasta daisy!! As noted, there are multiple cultivars of yellow flowered shastas and they have gotten quite popular in recent years. In addition to those already listed, It could be 'Broadway Lights' or 'Cream Puff'.