Four O’Clock

So if the five petals of a desert sand verbena flower (see previous post) are not really petals, what are they?

In order to answer that, I’ll need to review some basic flower terminology.

The reproductive organs of a flower (the pistil and stamens) are usually surrounded by petals, which are modified leaves, often brightly colored. Collectively, the petals form an inner whorl of parts that is called the corolla.

There is usually an outer whorl, too. This consists of sepals, modified leaves that are often, but not always, green, and surround the flower bud as it forms. Collectively, the sepals are known as the calyx.

Taken together, the calyx and corolla are called the perianth.

In some species, there’s another set of modified leaves at the base of the flower, in addition to the calyx and corolla, that are called bracts. The bright “petals” of poinsettias and flowering dogwood are examples.

Detailed, technical descriptions of flowers in the Nyctaginaceae will mention the perianth, but say nothing of the petals, because there are none.

What looks like five petals on the sand verbena flower is actually a single five-lobed tube formed by five fused sepals. This is typical for flowers in the Nyctaginaceae. Some sources state that the perianth comprises fused tepals; think of a tepal as an intermediate between a petal and a sepal.

Flowers in this family often have bracts as well; Bougainvillea is an example. The reproductive parts usually consist of a single pistil and five stamens.

The inflorescence is typically a cyme. Most species are forbs, though there are a few shrubs, trees, and vines. There are about 300 species in about 30 families, found mostly in tropical and warmer temperate regions of the world.

Several species of plants from the Nyctaginaceae are found in the Sonoran Desert, including the following.

Allionia incarnata

Trailing windmills is a forb with a vine-like habit, growing along the ground. It can be either annual or perennial. The species is found in the Chihuahuan, Sonoran, and Mojave deserts, and the southern part of the Great Basin Desert. There are two varieties, incarnata and villosa. I believe this one to be the later based on location reports in CalFlora and the USDA PLANTS Database. I don’t have sufficient detail to identify it based on plant characteristics.

This flower consists of three clustered perianths. Unlike most other species in the Nyctaginaceae, trailing windmill flowers stay open all day. Most species in this family have flowers that open late in the day, hence “four o’clock”.


Mirabilis laevis

Depending on which authority you consult, there are four to six varieties of this small shrub, commonly called wishbone bush or wishbone plant. I believe this one to be  retrorsa, but lack sufficient detail to say for sure; it could also be villosa. Both have similar ranges in the Sonoran, Mojave, and Great Basin deserts.

Sand Dune Show

The Sonoran Desert’s wildflowers range from belly-flower sized to big and showy. Here are two of the latter. Although honestly, I took a lot of belly shots anyway. It was a sandy belly, sandy elbows kind of week.

Oenothera deltoides
dune evening primrose, desert evening primrose, birdcage evening primrose

There’s a native Oenothera species for every state in the Union except Alaska. Dune evening primrose is more widespread than many of them, and more widespread than many of the species I found in Anza-Borrego; it ranges from the Chihuahuan Desert north through the Sonoran and Mojave Deserts to the Great Basin Desert in Oregon, and also somewhat inland and along the California coast.

The plants I saw spread out along the sand maybe as much as three feet, and stood up to about a foot tall. I’ve read that in other parts of its range desert evening primrose can stand up to three feet tall. It’s described by various sources as both an annual and a perennial, so I’m not sure what to conclude there. One thing’s for sure, in Anza-Borrego at least it grows in association with this next plant. Almost any time I saw one, the other was there, too. Or close by.

Abronia villosa
desert sand verbena

Desert sand verbenas are not actually verbenas, which are in their own family. It’s in the four o’clock family (Nyctaginaceae). It is similar in size and growth habit to the dune evening primrose, but with a smaller range, being mostly restricted to the Sonoran and Mojave deserts, and some inland and coastal areas in California.

Take a look at the flowers. Looks like each has five petals, right? Not really. Another botanical oddity. More on that and other desert plants in the Nyctaginaceae next time.



There are at least six different species shown flowering in the first photo, and one plant not flowering but clearly a seventh species (not counting the dead ocotillo). Click on it to see it larger. This was one of the neat things about the super-bloom: so many different species growing together, forming crazy bouquets.

Odds and Ends

Two more plants I found blooming in Death Valley. At first I found neither of them interesting, but the more I read – or the more closely I looked – the more I liked them.


sticky ringstem, valley ringstem
Anulocaulis annulatus

This plant is endemic to the Mojave desert. It’s a perennial with a shrub-like growth habit. The flowers are quite small; you really have to zoom in to see them.








yellow nightshade groundcherry
Physalis crassifolia

There are several plants producing edible fruits in the genus Physalis: tomatillo and Cape gooseberry. Also “groundcherry”, which I’ve seen on menus (and my plate) in trendy restaurants, but I’d hesitate to say that this particular groundcherry is one of the edible ones. As with the Apiaceae, the Solanaceae (deadly nightshade family) has some tasty, culinarily important species as well as poisonous ones.

This range of P. crassifolia is limited to the desert southwest. Like sticky ringstem, it’s a perennial with a shrub-like growth habit.

Have a look at this abstract from the Journal of Natural Products; it seems that P. crassifolia can produce compounds showing “potent antiproliferative activity” that may some day be used for treating certain cancers.