Ruellias in Central Texas

Adapted from somewhere else
Corrections are appreciated :)


About the Ruellias

Ruellias are sometimes called Wild Petunias, but they aren't Petunias so that's a LIE! They're named after Jean Ruelle, who was a French botanist and physician during the Renaissance Period. There are lots of plants named after botanists.
Most, if not all, will have the flowers that open for only one day—they open in the morning and fall off by the evening.

We are fortunate to have a great diversity of Ruellia species, some of which occur nowhere else in the 50 states. Take a look at these BONAP maps for a view of all the species and the ranges/distributions.

Important things to note

Key diagnostic characteristics

  • Inflorescence structure - axilary vs panicle topping the stem
  • Leaf texture - waxy, hairy, fringe on margins?
  • Leaf shape, oval vs ovate vs lanceolate


Left: Red circle shows where the stem tops off with a multi-flowered inflorescence (group of flowers). This will grow into a branched structure known as a panicle. There are some flowers coming from the nodes too, but it's the panicle coming out of the main stem that's important.

Right: Large blue circle shows one of the flower buds about to come out. Note that they are coming out at the same spot where the leaves come out, known as the node. The nodes are marked with the small blue circles. This arrangement is known as an axillary inflorescence. While these flowers aren't on a stalk (sessile, botanically speaking), sometime the flowers will be borne on a stalk, like on Mexican Ruellia.

Quick and easy-to-understand illustrated glossary of leaf terminology for your convenience

Most of these characteristics can be captured and seen within 1 or two photos. I would do one showing the flowering structure (inflorescence), and one showing the leaves and their texture/hairs. For leaf texture it might be good to note that down, but that's probably a bit excessive.

Here's a few example observations to look at:
Example 1
Example 2
Example 3
Example 4

Species Matrix

For those wanting to review in a glance. To be finished

Ruellia nudiflora Ruellia metziae Ruellia occidentalis Ruellia simplex Ruellia drummondiana Ruellia humilis
Inflorescence arrangement Terminal Terminal Terminal Axillary Axillary Axillary
Peduncled/stalked or sessile Peduncled Peduncled Peduncled Peduncled Sessile Sessile
Leaf shape Oval-ovate Oval-ovate-lanceolate Ovate, verging on deltoid Lanceolate-linear Ovate Oval-ovate
Leaf apex Rounded, sub-acute Rounded, sub-acute Sub-acute, often coming to a point; sometimes rounded Acute, often narrowly acute Acute to sub-acute Sub-acute to rounded
Stem & leaf indumentum Essentially glabrous; glabrescent Essentially glabrous; glabrescent Short-pubescence - canescent Essentially glabrous Short-pubescence Long-pubescence - pilose; margins cilliate
Corolla color Purple White, sometimes pale purple Purple Purple, pink, white, probably more (due to cultivars) Purple Purple to pale purple

I will organize the species based on whether the flowers are axilary or in a panicle.


Flowers on a panicle topping the stem


This is the most common of the Ruellias. Well, most common around here... outside of Texas they, occur sparingly in a few other states and down south to Mexico. You wouldn't know if you live within Austin or Dallas or anywhere in Texas deep within its range.
The flowers rise above the leaves in a flowering stalk, which is known as a terminal flower arrangement. Notice how the main stem continues upward and then branches out to multiple flowers.

Leaves are oval, with a waxy or glossy look to them. Essentially they are glabrous; they can have some hairs, but those hairs aren't very conspicuous or dense.


This species is named after Sister Mary Clare Metz, botanist and professor at Our Lady of the Lake University (OLLU). She has an interesting story: see here for more information.

This species looks exactly the same as Violet Ruellia... except the flowers are white. Actually, the corolla and calyx are also significantly larger than Violet Ruellia, though it can be difficult to tell from a photo unless one has a ruler on hand. Flower color is a relatively reliable way of IDing this one; I have heard that there is also a white form of Violet Ruellia, but I have yet to come across one.

R. metziae: corolla (fused petals) 5.5-6.5 cm long, calyx lobes 14-20 mm long when in flower:
R. nudiflora: corolla to 4-5 cm long, calyx lobes 10-15 mm long when in flower
Page 214 of Flora of North Central Texas, found here: https://fwbg.org/research/brit-press/illustrated-flora-of-north-central-texas-online/

Images showing difference in calyx size:


I plucked a Violet Ruellia flower just to make a point

The calyx lobes are almost always reliably longer for R. metziae, by ~5 millimeters.
Here's the calyx with a ruler beside it:

I collected some data on the size of the corolla and calyx and found that R. metziae flowers are indeed consistently larger than those of R. nudiflora See this observation for more information.

Detailed descriptions of both species:
Ruellia metziae
Ruellia nudiflora

Another feature which helps distinguish this species from R. nudiflora is the presence of long decurrent leaf bases (see the link for more info):

See that long "stem" that I pointed out with the bracket? That's known as the petiole, the part where the leaf connects to the base. Notice how long it is, maybe even half the length of the leaf it's part of! Decurrent is what you see in the red circle, outlined by the purple lines, where the leafy bits of the leaf runs down the petiole. Long decurrent leaf base. The leaves are also a longer sort-of elliptical/oblong shape, and might even look lanceolate. Check the illustrated leaf glossary if you need to check what those mean. If you look at the Violet Ruellia leaf image above, you can see how the leaves have a much shorter petiole and are more oval/short.


This species, like Metz's Ruellia and Violet Ruellia, has a terminal inflorescence, with its flowers coming out on a flowering stalk above the leaves rather than from the leaf nodes (axilary flowers). However, unlike the other two, the leaves are not glossy/waxy, but more matte in appearance, similar to Drummond's Ruellia. This is due to the presence of pubescence on the surface of the leaves. The leave blades are less oval in shape, and closer to an ovate/deltoid shape, wider towards the base and often coming to a pronounced point at the apex. They are also broader, generally about x1.25 or x1.5 longer than wide.

The flowering stalk is also densely covered in fine white hairs (canescent).

This species is rare in Central Texas, so if you find it that's a real treat! On iNat there are previous observations seen to the west, in Barton Creek and Emma Long Metro Park.


Flowers coming from the node (axillary)


This is a nonnative species from Mexico, the Caribbean, and Central/South America
It has been widely used as an ornamental and escaped from cultivated, where it is established in several southern states. It is considered an invasive in some places, particularly when it gets into riparian areas (areas near water).
Due to the many horticultural cultivars, the leaves can vary quite a bit, but typically are distinctly lanceolate (lance-shaped)


Notice how the flowers, while on a stalk, still come out of the leaf nodes

Sometimes they even tend to look almost grasslike.
(there are several cultivars)


https://www.inaturalist.org/observations/103579832

I see this plant every now and then in nurseries.


Named after the great botanist Thomas Drummond, who also has a lot of other plants named after him in Texas.

Drummond's Ruellia is a Texas endemic - aka, it occurs nowhere else but Texas. The species is mostly limited to Edwards Plateau and extending a bit up north to Dallas, as you can see on BONAP.

The leaves are ovate, rounded on one end and pointed on the other. They're covered in very fine hairs which makes them fuzzy to the touch.

The flowers also come out at the leaf nodes (where the leaf attaches to the stem) rather than coming out as a stalk from the top like Violet Ruellia. Note that they are practically sessile: no stalk/pedicel/peduncle, just coming straight out of the leaf axils.


Hairy Ruellia is, well, hairy. Hairy in a very conspicuous way. Each hair is long enough to pick out individually from both the naked eye and the camera. An easy way to see this is on the leaf margins (edge of the leaf) and the stem.

Publicado el septiembre 19, 2022 06:57 TARDE por arnanthescout arnanthescout

Comentarios

Thanks again for the great journal entry! One point of confusion I ran into initially was the calyx lobe length; it looks like you swapped the calyx lobe lengths for R. metziae and R. nudiflora when transcribing from FNCT.

Publicado por joefry hace más de 1 año

@joefry Oh no, I did! Ok, I fixed that up now, thanks for catching that. I've had problems mixing up character traits before... I still say alternate instead of opposite sometimes.

This journal post's a bit crude, but I figured it's better to get something out first and then improve it rather than spend forever perfecting it. Hoping I can update it (and some of my other ones) later.

Publicado por arnanthescout hace más de 1 año

Very nice summary.

Publicado por centratex hace 10 meses

Thank you. I'm usually a bit perfectionist when it comes to writing things, so while there are things to be improved I'm glad you approve of it :)

Publicado por arnanthescout hace 10 meses

I am curious about several oddball R. strepens observations in the area and have been doing a little digging. Just reading, not physically digging.

Publicado por centratex hace 10 meses

Yes, I have noticed some observations clustered in the SE side of Williamson county. I am not familiar with that species and don't recall how to differentiate it from R. drummondiana. I left them out from this post since they seemed very rare and restricted in location within the Austin area & Central Texas. Let me know if you find anything interesting, I am also curious about it.

Publicado por arnanthescout hace 10 meses

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