Violet Confusion: Which Species Are You?

What color is the throat of the violets in these photos?

Wildflower identification can be frustrating. How difficult can it be to identify the genus and species of a violet? Well, it's difficult. These two white violets look like different species to me. They could even be wild hybrids. But my main concern is which of three species of the genus Viola they are:

• Viola canadensis (Canada violet) which has a yellow throat and purple veins?
• Viola blanda (sweet white violet) (which seems to hybridize easily) with reddish stems?
• Viola pallens (Northern white violet) that is smaller than the others?

The violet below is probably the common blue violet (Viola papilionacea) but I hesitate to identify it as such because the description says it should have a white throat. If the feathery center is the throat, it's a common blue violet. If the purple blob beneath the feathery middle is the throat, then it isn't. Does anyone have any ideas? Every place I looked on the Internet assumes you know exactly where the violet throat is.

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