Puncture Vine

21 Jun

Tribulus cistoides




Puncture Vine (by John Bradford). The opposite (paired) compound leaves look ferny.

Puncture Vine (by John Bradford). The opposite (paired) compound leaves look ferny.

Friday John and George searched Halpatioke Park in Stuart Florida for botanical treats. They abound, including the parking lot weeds.  A striking non-native presence on the hottest driest sunbaked weedy sand is the botanical misfit known as puncture vine.  We’ve all seen it sprawling from a pavement crack across the asphalt with opposite ferny leaves and cheery yellow buttercup blossoms.  It is related to Vera Wood trees, similar in flowers and foliage.  Some may know Tribulus (terrestris) as a commercialized botanical “remedy” in a jar.  Others may know puncture vine from a foot stab mishap, the painful burr fruits similar in size, shape, and sensation to those from the sand spur grasses (CLICK).    An example of convergent evolution, as sandspur and puncture vine are unrelated despite superficial burr similarity.

Ouch.  Puncture vine fruit

Ouch. Puncture vine fruit

The puncture-prone fruits are armed to the teeth with teeth.  Another an apt name for the plant is caltrop.  A caltrop is an old fashioned device to hobble horses.  Anti-chariot technology. The puncture vine fruit is a little green caltrop.   It can poke a sneaker or a bicycle tire.  Even worse—the things you learn from Wikipedia—some warriors smear lethal arrow poison on the burrs and leave the deadly little booby-traps for unshod foes.

Caltrop (Google Images)

Caltrop (Google Images)


Let’s change the subject to something prettier. The attractive blossoms track the sun, all aligning toward the rays just like digitally coordinated solar collectors.



Why?  Explanations of floral solar tracking include the heat vaporizing floral fragrances, or to provide an attractive warm haven for pollinators.  Most solar tracking flowers live in cool places where such cozy advantages are obvious.   But why a solar-powered warm-climate weed?  I do not know.  Maybe extra heat helps at times even in warmer climates. It is not always hot year-round 24/7.  And maybe the species evolved in a cooler time or place. Or maybe the direct sunbeams somehow help bees orient to the flowers.   Yellow flowers commonly have UV patterns in the petals; bees see the patterns but we can’t—maybe those sun rays make the patterns pop to a busy bee.

tribulus Solar Dish Systems

The compound leaves and their leaflets track the sun too, ostensibly to maximize sun exposure for photosynthesis.  The entire ferny leaf orients toward the orb, and as a step further, the individual leaflets “cup” like tiny curved linear sun collectors.  In the image below the brown tilted stick tilts at the sun.  The leaves have the same inclination.

Leaves tracking the sun.  The stick (and leaves) pint to the sun.

The stick, flower, and leaves point to the sun.



tribulus pills


Posted by on June 21, 2014 in Puncture Vine, Tribulus


Tags: , ,

15 responses to “Puncture Vine

  1. theshrubqueen

    June 22, 2014 at 9:35 pm

    Trying to remember Botany 101…are these astic plants that bloom with the sun? I don’t think that is quite the right word..

  2. George Rogers

    June 23, 2014 at 10:19 am

    Well, that’s my word for the day. I teach Botany 101 (well, 1010 to be factual), and can’t bring the word to mind. Maybe nastic? Plants able to track the sun are generally called heliotropes.

  3. Chris Lockhart

    June 23, 2014 at 1:39 pm

    George, thanks for the interesting account on the heliotropic behavior of our beloved puncture vine 🙂 Another historic tidbit I recall from my Botany days at FAU – Dr. Dan Austin relayed that early populations were spotted near small airports. They may have been spread by the rubber airplane tires of the 1940s to their invasive status today. Despite their nasty burs, they still are a cool flower. I’ve got a Lignum vitae tree in my yard. Since they’re in the same family, I wonder if they also track the sun. Very interesting!

    • George Rogers

      June 23, 2014 at 6:17 pm

      Hi Chris, Sure…sticking to airplane tires is likely. And airstrips are perfect open, sandy, hot, disturbed low-maintenance habitats. The plant is all over parking lots and roadsides too…I doubt the burrs stick in the rubber that much, but probably jammed up in the treads, and there perhaps reinforced by the teeth. I’ve never heard of a sun-tracking tree, but that fact carries little weight, and you never know. And in the cuffs of my pants.

  4. Beth

    June 23, 2014 at 2:05 pm

    Fascinating once again. Thank you, George and John.

    • George Rogers

      June 23, 2014 at 7:30 pm

      Yo Beth, Your picture is still on our old website —

      • Beth

        June 28, 2014 at 3:26 pm

        (my only claim to fame 🙂 hey, I still think back to that day when I see Digitaria longiflora or Paspalum conjugatum, and many others

  5. theshrubqueen

    June 23, 2014 at 2:34 pm

    Heliotrope, Oh good, more latin words. I had Botany in 1980, so it is probably called 1010 now. I have been searching for my copy of Hortus Third, I will look for that word and let you know if I find it.

    • George Rogers

      June 23, 2014 at 7:30 pm

      Maybe the secret word is “nastic.” Nastic movements are non-directional, as opposed to tropisms, which are directional, as in sun-tracking.

  6. Chris Lockhart

    June 23, 2014 at 6:19 pm

    Thanks, George!

  7. uma Bhatti

    June 26, 2014 at 8:56 pm

    Puncture vine is my favorite. can i grow in my yard dr rogers?

    • George Rogers

      June 26, 2014 at 9:00 pm

      Sure—hot, dry sand. Do you see it ever in India?

    • Chris Lockhart

      June 26, 2014 at 11:08 pm

      While it is pretty and very adaptable, even in very disturbed areas, I would caution against planting it. It is a Category II invasive plant and has escaped and invaded our natural areas in many parts of FL, especially from the FL Keys to Palm Bay/Melbourne. Check out and zoom in to south FL to see.. There are many other areas that don’t get reported, too.

    • Chris Lockhart

      June 27, 2014 at 1:35 pm

      and save you having to deal with those nasty burs! 🙂

  8. George Rogers

    June 28, 2014 at 4:08 pm

    Beth, oh yea, let’s see, how DO you tell those apart….?


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s

%d bloggers like this: