Kallstroemia parviflora hugs the ground with hairy to glabrous stems and leaves. Golden-yellow flowers appear from July through October. Fruits are ovoid and hairy with a persistent beak longer than the the fruiting body.

The plant at first glance might be taken for Tribulus terrestris (see below), but Kallstroemia's leaflets are wider, the fruit splits into 10 instead of 5 nutlets, and the fruit is not spiny.

The plant was named and described by Scopoli in 1777 and the genus name honors Scopoli's contemporary, Anders Kallström (1733-1812). "Parviflora" means "small flower".

Zygophyllaceae has many genera outside of the United States, but here in the U.S. it has just five genera and but one famous member, Larrea tridentata, Creosote Bush.

Kallstroemia parviflora was first collected by E. Wilkinson in Texas in 1897 and was named and described by J. B. Norton in 1898.

Kallstroemia parviflora (Caltrop)
Zygophyllaceae (Caltrop Family)

Semi-desert. Openings, disturbed areas. Summer, fall.
San Juan College, New Mexico, September 20, 2013.

Stems are most often hairy, stiff, and reclining. Five petals are golden yellow and longer than the five sepals which are hairy. Stamens are 10.

The white arrows point to the green stipules (leaf-like appendages at the base of a leaf petiole).

Tribulus terrestris (Puncture Vine, Goathead)
Zygophyllaceae (Caltrop Family)

Semi-desert. Openings, disturbed areas. Summer, fall.
Above: Canyons of the Ancients National Monument, August 9, 2016.
Left: Near San Juan College, New Mexico, September 20, 2013.

This alien plant spreads quickly over large areas. Its leaves are divided into small leaflets, flowers are attractive yellow, and its seed pods are horrific. Notice the sharp points developing on the seed pod immediately to the left of the yellow flower in the photograph above.

Although Tribulus terrestris is similar to its cousin shown at the top of this page, it differs in several ways: leaflets are about half the size of Kallstroemia parviflora, it has 5 instead of 10 nutlets, and its nutlets are terribly spiny (hence the common name).

Tribulus terrestris is an invasive species that should be pulled out and burned or placed in the garbage. Seeds are viable for almost a decade, so don't compost the plant. As the map below indicates, the plant is on the noxious weed list in many states.

The genus and species were named by Linnaeus in 1753 from southern European collections. "Tribulus" is from the Latin and Greek for "three-lobed", as in the caltrops weapon, three-spiked iron balls used in warfare. Individual seed capsules of T. terrestris have two or three spikes and are reminiscent of caltrops, hence the name.

Tribulus terrestris (Puncture Vine, Goathead)
Zygophyllaceae (Caltrop Family)

Semi-desert. Openings, disturbed areas. Summer, fall.
San Juan College, New Mexico, September 20, 2013.

Plants spread low to the ground.

Tribulus terrestris (Puncture Vine, Goathead)
Zygophyllaceae (Caltrop Family)

Semi-desert. Openings, disturbed areas. Summer, fall.
San Juan College, New Mexico, September 20, 2013.

Flowers have attractive arrangements of ten stamens in two ranks surrounding the five-parted, green, inflated ovary which is topped by the yellow/green inflated stigma.

Tribulus terrestris (Puncture Vine, Goathead)
Zygophyllaceae (Caltrop Family)

Semi-desert. Openings, disturbed areas. Summer, fall.
Canyons of the Ancients National Monument, August 9, 2016 and
Near San Juan College, New Mexico, September 20, 2013.

In the top photograph at left you can see the green seed capsule beginning to dry with its sharp spines already drying to a light grey.

In the upper half of the second photograph at left, you can see the long, sharp, stiff spines of two dry fruit capsules -- lurking in the sand, waiting for a bicycle tire, hungering for humans on a picnic. Of these painful projections Stanley Welsh writes, "This tribulation of the earth is a vicious weed, leaving in its wake a refuse of punctured tires and painfully injured feet; it is indeed adequately named scientifically". Welsh tells us that the earliest Utah record of this tribulation was found along the railroad in Salt Lake City in 1920. Ninety years later it made its way into southwest Colorado.

Range map © John Kartesz,
Floristic Synthesis of North America

State Color Key

Species present in state and native
Species present in state and exotic
Species not present in state

County Color Key

Species present and not rare
Species present and rare
Species extirpated (historic)
Species extinct
Species noxious
Species exotic and present
Native species, but adventive in state
Eradicated
Questionable presence

Range map for Kallstroemia parviflora

Range map for Tribulus terrestris