My grandmother used citrus for a lemonade-like drink she called calamondins and I assumed were calamondin oranges (they're round, not squat). The fruit look like small oranges and have thick rinds and big seeds and have their own unique flavor. I bought two trees from Lowe's that were labeled calamondin oranges, but the fruits of those trees are like giant kumquats: they have thin skins and small seeds and they taste like kumquats. Was I wrong in thinking the fruit from my grandmother's tree were calamondin oranges, or did Lowe's rip me off?

I think you should share foto so that we can help you.

http://users.kymp.net/citruspages/kumquats.html#calamondin

Tiberian, a Calamondin is not an orange. It is exactly what Lowe's has sold you:

http://www.citrusvariety.ucr.edu/citrus/calamondin.html

They are quite sour like kumquats, and have kumquat in their genetics. Native to the Phillipines. The fruit is round and a little larger than kumquats. Perhaps your mom was calling another cultivar by an incorrect name?

I know a calamondin isn't an orange, but there are two types of fruits called calamondins: ones that are more squat like tangerines that are simply called calamondins, then there are ovoid ones called calamondin oranges. Here is one of the fruits from my grandmother's house. I don't have any of the ones from the Lowe's trees left.

Probably a kumquat hybrid (mandarinquat?) but definitely not a calamondin...

Broadly speaking Marc is correct it is a mandarinquat.

Within that group is the calamondin
This is thought to be a sour mandarin kumquat hybrid. It is zygotic so some variation is expected. Indeed the calomondin of s. China differs from the kalamansi of the phillipines and plants grown under that name in europe and america. Overall calamondin is a seedling grex showing differences in thornyness, precoscicity,fruit size and shape.

The term mandarinquat is liberally applied and usually has nagami kumquat as the seed parent, as the pollem parent is usually unknown they are sometimrs also identified as orangequats. Examples being indio mandarinquat or nippon orangequat.

Although the fruit from your grandmother"s tree does not look like the calamondin I see here in europe it or the plant you purchased from Lowes may be a seedling and still within the varieability of the grex.

You are absolutely correct as regards calamondin as it is available in europe where it looks like a small mandarin sometimes with a loose skin, sometimes adhering more tightly. Always acid and seedy. This type is propagated by cuttings and therefore quite uniform. It is comparable to the form found in s.china, hong kong,tiawan and surrounds. The plant you will find in the chinese markets around chinese new year and unbiquitously elsewhere. This I think is the lowes plant.

The fruit is at the other end of the grex and showing more kumquat characteristics. I am not that familiar with the kalamansi but think it is of that type. It also goes under different names such as phillipines orange which goes to explain the inclusion of orange along with calamondin. Marketing may be another way that orange gets included alongside calmondin, laziness nursery doesn"t have explain what they are selling.

Still think both plants are calamondin within the boundaries of the grex.

Tiberian Friend, can you compare the foliage of the two types?
Maybe post a photo?
Calamondin has fairly unique foliage, and leaf scent should be able to compare with the C.O. to see how close they appear.
ps Is your Gran's plant unique ? Surely if you propagate from it, you will get exactly what you are after?

I'll try to get some images of the leaves of the tree at my grandmother's house next time I'm there, but it'll be difficult to find ones that aren't disfigured by disease. I've seen similar fruits on Google image search, so I doubt it's a unique plant.

I bought the trees from Lowe's because they were already grown enough to flower. My sister is growing a tree from a seed of one of the fruits, but there are so many different citrus trees around, there's no telling what she'll get.