Subject: 9.34  Thorns aka Puncture Vine
From:  Jobst Brandt <jbrandt@sonic.net>
Date:    Thu, 21 Sep 2000 16:54:00 PDT

Not all riders suffer from thorns which seems mainly to be a function
of avoidance rather than luck or protective means in the tires.
Rather than searching for tires or sealants that will survive thorns,
recognizing the plant is a more effective step toward avoiding flats.
The plant is not mobile and does not propel its seed pods away from
its tendrils.  However, some riders think nothing of pulling thorns
from their tires and throwing them on the road as they patch their
tires.  This practice seems to be part of not understanding avoidance.
In my experience, riders who suffer most from thorns, have no idea of
the plants appearance or its habitat.  Most, think the yellow star
thistle is puncture vine which it is not and it cannot penetrating a
tire.

Puncture vine, tribulus terrestris, grows mainly on barren soil,
typically on roadsides that have been sprayed with herbicides to
prevent grass fires from discarded but burning cigarettes.  The plant
germinates after the heat of summer has begun and grows from a central
tap root that reaches as deep as three meters.  It has flesh colored
tendrils that radiate 30 to 50 cm with 1 x 3 cm dark green compound
filigree leaves that follow the sun.  Its 1 cm diameter blossoms with
five yellow petals produce spherical seed clusters that separate into
five hardwood seed pods when ripe.  Each pod or segment has two 6 mm
long thorns extending from the top of the arches so that gravity will
make one of the two thorns point upward.  The plant produces seeds
throughout its annual growth.

Some examples:

http://www.cwma.org/puncturevine.html

http://www.or.blm.gov:80/Prineville/weed/puncture.htm

http://tinyurl.com/d0xo