Scutellaria drummondii vs Scutellaria wrightii

I find these two species can sometimes get confused in the Central Texas area... I myself didn't really understand these two very well, but I have a basic understanding of how they can be differentiated.


What to take photos of

To get the best evidence to ID these two, I would recommend taking a photo of:

  • a clear side/lateral shot of the flower, with corolla, calyx and stem in focus.
  • an overall shot to show the habit of the plant

Differentiation via the texture of the calyxes

S. drummondii will have long hairs, noticeable pubescence on the calyx ("spreading-pubescent or pilose" as Shiner and Mahler's Flora of North Central Texas says). S. wrightii will have short hairs; any pubescence is inconspicuous to the naked eye ("short-pubescent with inconspicuous hairs").

Left is S. wrightii; right is S. drummondii

This is my preferred method to distinguish these two species. However, if the calyxes are very out of focus it can be near impossible to tell.

Differentiation via the shape and orientation of the corolla

S. wrightii usually has a noticeable curve at the base "like a little pipe". The lower half of the corolla also remains very narrow, before it rapidly expands outwards. This also causes the corolla to be flexed upwards, so that it projects perpendicular to the calyx and almost vertical in orientation.
S. drummondii appears to lack this feature, projecting close to horizontal from the stem, and widens more gradually from the base, forming a sideways V-shape.


Differentiation via the size of the corolla relative to the leaves

This is from my own personal observations, so take this information with a grain of salt.
S. drummondii tends to have a corolla size that is not much larger than the surrounding leaves—at most I would say 1 1/2 times larger.
S. wrightii appears to have a corolla size that can often exceed the size of the leaves by a lot. This might be because the leaves at the end of the stems are younger and smaller than the base, and the large flowers tend to be clustered near the top. Or that since the corolla curves upward, it tends to extend up past a leaf node (or even two). Flowers further down the stem can be more proportional in size to the leaves. But often when looking at the plant, especially when well into bloom, the flowers really tend to dominate the scene.


Differentiation via the habit

When the plant is mature, the stems of S. wrightii are often densely clustered together, forming a tighter clump than S. drummondii does. S. wrightii is also a perennial—a woody perennial. On older plants, there will often be dead stems from previous seasons still visible. S drummondii is an annual, and, as far as I have seen, does not form woody stems.


Differentiation via surrounding soil

Alone this may not be a definitive ID feature, but it is a good clue.
S. wrightii is a inhabitant of poor, dry soils, often rocky and surrounded by bits of limestone. The soil color will usually be quite light in color. Apparently it can also be found on sandy soils as well. S. drummondii is less picky and will grow in clay and loam soils as well as sandy and limestone soils. You will probably not find S. wrightii growing on clay or loam... perhaps that's why it remains mostly limited to the Edward's Plateau... though its range does stretch upwards towards Dallas and Oklahoma.


Example observations:
S. drummondii:
https://www.inaturalist.org/observations/3020196
S. wrightii:
https://www.inaturalist.org/observations/4088602

Resources:
https://fwbg.org/research/brit-press/illustrated-flora-of-north-central-texas-online/ - Dicots: Fabaceae to Zygophyliaceae, page 778
https://www.inaturalist.org/observations/75992067#identification-84b1d42a-0054-4f8c-8f47-90742f13d4fc
https://www.inaturalist.org/observations/22646848

Also with the amount of times these can get mistaken for Texas Sage (Check out the Dave's Garden plant file!) I should add in a separate note about how to distinguish those too, but I can do that later.

Posted on March 27, 2022 04:30 AM by arnanthescout arnanthescout

Observations

Photos / Sounds

What

Wright's Skullcap (Scutellaria wrightii)

Observer

arnanthescout

Date

April 18, 2021 03:11 PM CDT

Description

This specimen has larger blooms than the others I'm used to.

Photos / Sounds

What

Wright's Skullcap (Scutellaria wrightii)

Observer

arnanthescout

Date

April 18, 2021 04:42 PM CDT

Description

Ok. This plant seems more massive, has larger flowers than Scutellaria drummondii. I think it's this species. Any other differentiating factors here?

Photos / Sounds

What

Drummond's Skullcap (Scutellaria drummondii)

Observer

arnanthescout

Date

April 2, 2022 05:15 PM CDT

Photos / Sounds

What

Drummond's Skullcap (Scutellaria drummondii)

Observer

arnanthescout

Date

April 11, 2022 05:34 PM CDT

Comments

Thanks, this helps a lot!

Posted by joefry about 1 year ago (Flag)

You're welcome @joefry! I'm glad this came in handy

Posted by arnanthescout about 1 year ago (Flag)

Thank you for this!

Posted by atlasmira 10 months ago (Flag)

This is terrific! Thank you. I have been scratching my head over these two species for some time and your post really clarifies things.

Posted by etlebsack 3 months ago (Flag)

Note: When one gets into the Rolling and High Plains area, you get a very similar species to Scutellaria wrightii, known as Scutellaria resinosa. They are apparently largely allopatric (ranges don't overlap) and can be only distinguished through careful study of the minute hairs on the stems and calyx (see Flora of North Central Texas for key and some discussion).

Turner's treatment and discussion: https://www.biodiversitylibrary.org/page/13797453#page/35/mode/1up
S. resinosa - 377
S. wrightii - 380
Range maps - 358, 360

In Central Texas/the Edwards Plateau (where I typically am) S. resinosa is not present and should not be of concern. I have suspicions that many observations around the Panhandle and into parts of Oklahoma that are S. wrightii might actually be S. resinosa but I haven't the heart to go through and check them all.

Posted by arnanthescout about 2 months ago (Flag)

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