Wednesday, September 9, 2009

Virginia Creeper / Woodbine

Many people would look at the two photographs below and call both plants Virginia Creeper or Woodbine, Parthenocissus quinquefolia, without as much as a second thought. But let's take a closer look. Below, I will explain how these two plants can be morphologically separated into two distinct species.


The plant in the photograph above is Parthenocissus quinquefolia, while that in the photograph below is P. inserta (which is treated as a synonym of P. vitacea by some authors, though the nomenclature of these two is quite confusing).


One thing to notice is that the leaflets of P. inserta are more shiny above than those of P. quinquefolia, which often appear dull on the upper surface.


Looking at the undersides of the leaflets, those of P. quinquefolia (above) are almost always pubescent, while those of P. inserta (below) are more often glabrous. There is, however, a rare hirtellous form of P. inserta known as P. inserta f. dubia.


Another part of the plant to check is the junction of the petiolules with the petiole.


In P. quinquefolia (above), this junction is also pubescent; in P. inserta (below), the junction is glabrous.


Growth habit is yet another way to distinguish between these two similar species.


Parthenocissus quinquefolia (above) is often high climbing, but it can also be found growing at ground level. Parthenocissus inserta (below), however, sprawls over the ground, structures, or other vegetation.


The reason for this difference in habit is all in the tendrils...


The tendrils of P. quinquefolia (above) have several branches that end in dilated adhesive discs, which are used to attach to vegetation or structures, allowing the plant to climb. Those of P. inserta (below), however, have few branches and no adhesive discs, and it therefore does not have the ability to climb the way that P. quinquefolia does.


Finally, if you are lucky enough to have flowers or fruit, the distinction between these two species is simple. However, as Swink and Wilhelm point out in Plants of the Chicago Region, P. quinquefolia rarely produces fruit, while P. inserta produces fruit routinely.


As you can see in the photograph above, the inflorescence of P. quinquefolia has a distinct central axis, with 25-200 flowers/fruit in panicled groups of cymes. The inflorescence of P. inserta (below), however, is dichotomously branched and therefore does not have a central axis. It most often has 10-60 flowers/fruit per inflorescence. The fruit of P. quinquefolia are a bit smaller in diameter than those of P. inserta, as well.


It's as easy as that. There is no longer an excuse for lumping all members of the Vitaceae with five palmate leaflets into P. quinquefolia. Now that you can distinguish between mature plants of Parthenocissus, be sure to check The Vasculum to see how to determine the difference between Parthenocissus and Vitis in the cotyledon stage.

12 comments:

Keith said...

Wow, who needs a text book with Scott and Justin around? Excellent post, Scott, and excellent photos!

Scott said...

Thanks Keith. Glad you enjoyed the post and photos. It is helpful that both species are on our property so I can study them closely.

Justin Thomas said...

Sweet post, Scotellaria. I hadn't seen verifiable P. inserta until my trip to the dunes last spring. It is nice to see the characters so well explained.

Scott said...

Thanks Justin. That was also the first time I had felt good about calling it P. inserta, other than right along railroad tracks. Possibly the first time I have ever seen P. quinquefolia in fruit was when I took the photos for this post... that's part of what prompted me to post on this topic.

Justin Thomas said...

This post is probably too buried to comment on, but I just check USDA Plants Database and found that P. inserta is considered a synonym of P. quinquefolia. So that means it no longer exists and this post is moot (wrote in the tone of sarcasm).

Scott said...

I'd be interested to know where they are getting their information. They seem to be using the name P. vitacea for the entity I called P. inserta in my post. Several of my resources show these two to be synonyms. However, nowhere can I find a resource (other than the USDA database) that shows P. quinquefolia and P. inserta as synonyms. The USDA database shows both P. quinquefolia and P. vitacea in northern Indiana, so I'm pretty certain that they are recognizing what I am calling P. inserta (as P. vitacea). Of course, vPlants is down, so I can't see how they are currently handling these species.

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Scott Namestnik said...

Wow Nicole... I had no idea that my discussion on Parthenocissus would get you that excited...

Justin Thomas said...

Hilarious! To each their own.

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Thunderpaws said...

I have a woodbine and a Virginia creeper. Two differences that I noticed: 1) The woodbine grows its new leaflets on the old wood, yet my Virginia creeper restarts at the base each year, albeit a little fuller. 2) The woodbine is not nearly as colorful in the fall. My Virginia creeper turns very deep red and provides a short-lasting accent to my garden.

Scott Namestnik said...

Interesting observations... thanks for sharing these. I'll watch for these characteristics.