|The Question: This wildflower is new to me and not one I have ever seen before in the Texas Hill Country. The plants have invaded my garden and are very lush and hearty. I’ve not seen them anywhere else in the pasture. The plants are almost shoulder high and I was expecting a big bloom to follow the quick growth but instead there is only a small flower tassel. What is this plant is called?
Submitted by: Betsy, Texas, USA
The Short Answer: Thanks to Jay at wildflowersoftexas.com for identifying this as Oenothera curtiflora (formerly called Guara mollis or Guara parviflora), also known as lizardtail or velvetweed. It’s a member of the Evening Primrose family (Onagraceae). Oenothera curtiflora ranges across much of the southwestern U.S., and Texas.
More Information: There about 125 species in the genus Oenothera, many of which have flowers that open at night, hence the name Evening Primrose. The other interesting thing about this group is that many of them can “self,” the term botanists use for plants that can fertilize their own flowers. Self-fertilizing in plants, like asexual reproduction in animals, loses the genetic benefits of sexual reproduction, but it has its plusses. For example, botanists consider some plants to be “pioneer species.” These species take advantage of disturbed habitats, such as burned out fields or forests. Or areas where the soil has been disturbed and other plants removed – otherwise known as “gardens.” Pioneer species are the first to colonize habitats that have been stripped of other plants.
But there’s a problem with being a pioneer. If you are the first – and only – plant of your species to sprout and grow in a new location, let’s say because a bird dropped your seed there, or the wind blew your seed there, who will you “mate” with? If you need another member of your species to cross-pollinate, you may reach the end of your lifespan without ever reproducing. You could wait to see if another seed of your species ends up in the same place as you, but you may only have a limited time before the original stable fauna regenerates and your opportunity as a pioneer is gone.
If you are able to fertilize yourself, you can produce seeds, and soon the disturbed habitat (Betsy’s garden) is covered by your offspring. They will have little genetic variation, which has its downsides, but it’s better than dying without reproducing.
Most plants can’t self fertilize because they have physical or genetic mechanisms to prevent it. But in some plant families, the mechanisms against self fertilization seem to be susceptible to simple genetic mutations that deactivate them, allowing self fertilization. And sometimes, in those same species, it’s relatively easy for another mutation to turn the self fertilization off again. Over the eons, this might give some lineages of these plants an advantage – especially as pioneers. If they can switch back and forth between self fertilizing and sexual reproduction, they might gain the benefits of both.
That seems to be the case with the Oenothera. Dr. Kyra N Krakos of Maryville University in St. Louis studies the Oenothera (she confirmed that Betsy’s picture is Oenothera curtiflora). She believes the 24 species in the Oenothera lineage that includes O. curtiflora has switched from sexual reproduction to selfing at least six times.
“That many transitions to selfing in a small group of species suggests that breeding system in this group is highly changeable. And it may play a role in the high rate of speciation in the Oenothera. Oenothera curtiflora is a widespread species and it handles really tough environments (rough weather, low water, highly disturbed) so well. Those kinds of conditions favor selfing species. Basically, being self compatible is a good trait in stress environments, and the Oenothera in this group have an evolutionary history that suggests the ability to switch to selfing when needed.”
A garden is the perfect stress environment for a pioneer species. It is highly disturbed and the established plants have typically been removed. And yet, unlike the marginal habitats where pioneers usually find themselves, the garden is not dry or lacking nutrients.
And that, friends, is why gardeners fight a never ending battle against weeds (otherwise known as pioneer species).
Kyra Krakos. The evolution and reproductive ecology of Oenothera (Onagraceae). PhD Dissertation at Washington University in St. Louis. Downloadable at http://openscholarship.wustl.edu/cgi/viewcontent.cgi?article=1600&context=etd
USDA site with information on Oenothera curtiflora: http://www.ars-grin.gov/cgi-bin/npgs/html/taxon.pl?458529