KYBBY ID Tips: Nabalus altissimus and Viola palmata Veg ID
Although the two are not closely related at all, basal leaves of tall rattlesnakeroot (Nabalus altissimus, Aster family) and palmate or early blue violet (Viola palmata, Violet family) can be mistaken for each other at first glance. Both species can be variably hairy, both have lobing that is highly variable, and they're both common across the state and are found in the same habitats. How's a botanizer to recognize each for what it truly is? Let's first look at the variability seen in each species, then I'll show you the easy, fool-proof way to tell these two apart.
Palmate or Early blue violet, Viola palmata
V. palmata is a "stemless blue" violet, a subgroup of violets that all feature basal-only foliage with usually blue-purple flowers, and there are around 10 constituent species of this subgroup present in Kentucky. This is what is known as a heterophyllous violet species, or one with different leaf forms (from Greek, heteros = different, phyllon = leaf). Typically, the earliest couple of leaves that emerge for this species are cordate (heart-shaped) and virtually indistinguishable from plain old common blue violet, Viola sororia. But each successive leaf that emerges is increasingly lobed and dissected, so by summer an individual plant may have a whole cluster of variably shaped leaves. Here's what that progression often looks like:
This rosette has several heart-shaped leaves, but the lower edges of the freshest-looking leaf held by @hbraunreiter are showing signs of what's to come.
Here in @biomania's photo you can see the leaves becoming distinctly lobed, although there are still one or two heart-shaped leaves present.
Finally, here's an example of a summer leaf seen by @destes, where the lobes are dissected all the way to the petiole. Sometimes the early heart-shaped leaves are still present, sometimes they disappear by this time.
Tall rattlesnakeroot, Nabalus altissimus
There are 7 Nabalus species present in Kentucky: four of them are rare, two are uncommon or only present regionally, and then there's Nabalus altissimus which is common and present throughout most of the state.
Similar to Viola palmata, the earliest leaves are unlobed, although for Nabalus they're a more triangular or arrow-shaped, and they usually have several widely-spaced teeth along the edges as seen in this observation from @emwachter
It doesn't take long for 3-lobed leaves to emerge, like the ones seen here by @mikaylagroce https://www.inaturalist.org/observations/22515308
The exceptionally variable summer foliage can look like anything from this 3-lobed specimen seen by @jmashburn, to this 5ish-lobed individual seen by @ecruz0911, to a skinny-minnie observed by @nyssa_ogeche, with A LOT of room for variation in between.
How we tell 'em apart
Given the wild variability and overlap in leaf shapes, what's the feature that removes all doubt? The answer takes us back to their familial connections: Nabalus is a member of the Cichorieae tribe (a taxonomic level between family and genus) in the Aster family. And all members of this tribe including notable species like chicories, lettuces, and dandelions have white, milky sap, while all violet species have clear sap. You can see easily see this by tearing piece off a Nabalus leaf; here's @etantrah capturing it emerging from a stem:
Hope this helps you the next time you're confronted with an ambiguous basal leaf that looks like it might be one or the other!
