Weeds–Nature’s Emergency Technicians: No. 1. Alkali Heliotrope

Introduction to the Weeds

While I studied vegetation ecology at Arizona State University, my boys and I would sometimes walk the two miles from our apartment to campus to pick up mail and assignments. We lived just north of the Salt River, once a fine desert stream that modern dams and diversions turned into a dry riverbed. We would enter the river channel a few blocks from our apartment and amble along for a mile and a half until we neared the campus. That hike was one of our favorite times together. The channel held scattered and battered Cottonwood trees, Mesquite, Seepwillow, Acacia, clusters of Squawbush, Brittlebush, Ambrosia, thickets of Sunflowers, the mighty Mullein, patches of feathery Storksbill, curly Heliotrope, lots of bare ground, and a million stones rounded by their history tumbling down the river. I think it was during those hikes that my oldest boy (age nine) developed the accuracy and strength to pitch for a series of baseball teams.

Between rock throwing attacks on old tires and washing machines, we saw birds, rodents, and lizards, but no people. In all the times we walked down the river to the urban campus of 40,000 students and thousands of staff, we never met another human. People weren’t there because our society considers such places as the Salt River’s dry riverbed as unlovely wastelands. And the unique and fascinating plants living there are a universe away from the cars and streets and affairs that fill our time.

Weeds are the most dynamic members of the botanical world. The many ways they disperse their seeds and smite their competitors are often unexpected and enlightening. Weeds’ ability to colonize and thrive in damaged and hostile environments suggests that they will be the plants that survive the Anthropocene. Some weeds will make fine companions for any of us that survive, but some weeds would be inimical to humans and other animals.

Weeds evolved the ability to colonize and flourish after natural disturbances long before humans appeared. Natural selection polished the special traits of weeds for millions of years before we branched out in the primate tree and learned to herd, farm, and build. For weeds, the breaks in nature due to livestock trampling, plowing, and building are the same as natural disasters.

Weed traits include dispersal and growth mechanisms that let them succeed in damaged habitats. As the number of farms and domestic animals increase, the places suitable for weeds also increase. Once a small band of specialists living in the relatively tiny naturally disturbed sites, weeds have increased their numbers to become a dominant species group.

I want to report what I’ve learned about weeds, and I want to describe some of the weeds that live near my home. Here’s a link to some articles I’ve written about weeds. I don’t plan to use unusual words, but a few terms are useful. Here’s a link to weed anatomy drawings and definitions. The first weed I’m covering is:

Alkali Heliotrope (also known as Quail’s Delight).

Alkali Heliotrope (Quail’s Delight) Heliotropium curassavicum var. oculatum. A. Pair of flower spikes. B. Young fruits. C. Fruit composed of four small brown nutlets about 1/16 inch long. D. Single nutlet. Older flowers are at the fork of the uncoiling spikes. A native perennial, the plants spread to form protective carpets over bare ground. Drawing: Lucretia Breazeale Hamilton. Copyright (c) 1972 The Arizona Board of Regents. Reproduced from Parker (1972) with permission of the University of Arizona Press.

Alkali Heliotrope (Quail’s Delight)
(Heliotropium curassavicum var. oculatum ).

Alkali Heliotrope’s tiny fragrant flowers delight bees and gnats. The uncoiling spike, a flower-studded fiddleneck, reveals little beauties pure white with yellow-green eyes that purple in sunlight. This bluish green perennial grows to about one foot, but mostly it forms flat patches of overlapping branches up to four feet wide. The plants are hairless, but lightly dusted with a white powder that easily rubs off.

A native of arid North America, Quail’s Delight can edge into a lawn or garden. Removal by pulling is a simple cure, but the plant has no thorns or burrs and you might wish to leave it on unused sites where it will protect your soil from wind and water erosion.

The plants colonize exposed alkaline or saline soils and the banks of streams and washes in arid western U. S. and Baja California. You will find similar varieties around the world. I’ve seen this one growing beside a canal in Tempe, Arizona, and a very similar variety beside limestone rocks near Fourteen Mile Creek in Oklahoma.

Alkali Heliotrope flowers. © David Eickhoff (License: CC BY 2.0)

 

Weed No. 2. Annual Bluegrass (Poa annua)

Weed

A Spectacular Thug Is Out of Control

GR: As I’ve often reported, only construction and total habitat destruction have done as much as invasive plants and animals to reduce global biodiversity and productivity. Introduction of invasive species is continuing its impact and the rate is accelerating. Global warming is gaining fast, and will combine with the others of the human impacts to push the human impact on the Earth to extremes that will require millions of years of recovery after we are gone. Here’s a report by Paul Simons on an invasion that will take years of intense labor to stop.

Invasive rhododendron ponticum spreading on the Isle of Mull, Scotland. Photograph: Mark Boulton/Alamy Stock Photo

“Rhododendrons are flowering now in a magnificent springtime spectacle – but they are thugs, invading some of our finest and most precious countryside with catastrophic impacts on wild plants and animals.

Rhododendron ponticum was first brought to Britain, probably from Spain or Portugal, around 1763 for botanical gardens and used on big estates as cover for game birds. But the shrub has spread out of control with huge damage to many native woodlands, heaths and other wild places like the Snowdonia national park. The plant now covers 98,700 hectares, roughly 3.3 per cent of Britain’s total woodland, a report by the Forestry Commission found, and Scotland has been hit particularly hard, where it covers 53,000 hectares.

Rhododendron grows into huge bushes with thick vegetation that blocks out sunlight and smothers most other wild plants and trees, stopping them from growing or regenerating. Its leaves are toxic to animals and repels wildlife from earthworms to birds. Many bushes have become infected with the highly pernicious tree disease called sudden oak death that threatens many types of trees and shrubs. Outbreaks of the disease in the UK, especially on larch trees, have often been linked to Rhododendron ponticum.

“Each plant can produce one million or more tiny seeds each year that spread in the wind, and it also spreads with massive tangles of branches rooting in the ground. The plant is incredibly difficult to get rid of by digging up or using herbicides. Snowdonia national park and several other sensitive areas have tried to destroy the invading rhododendron involving hundreds of people over many years digging up the plant. It’s expensive, time-consuming and takes years to completely eradicate.” –Paul Simons (Source: A spectacular thug is out of control | Science | The Guardian.)

Rapid version of assessment tool provides easier way to monitor wetland quality

A modified or ‘rapid’ version of an existing wetland assessment tool can accurately assess the quality of wetlands, according to researchers. Using the rapid version of the tool, known as the Floristic Quality Assessment Index, can save time and improve upon wetland monitoring strategies. www.sciencedaily.com

GR:  This article gives citizen naturalists tools for assessing the health of their neighboring wetlands.

Theory of ‘smart’ plants may explain the evolution of global ecosystems

“It’s easy to think of plants as passive features of their environments, doing as the land prescribes, serving as a backdrop to the bustling animal kingdom.

“But what if the ecosystems of the world take their various forms because plant “decisions” make them that way? A new theory presented by Princeton University researchers in the journal Nature Plants suggests that in some cases that may be exactly what happens. In one of the first global theories of land-biome evolution, the researchers write that plants may actively behave in ways that not only benefit themselves but also determine the productivity and composition of their environs.

“Our theory explains biomes based on the new idea that we must consider plants to be smart and strategic,” said senior author Lars Hedin, a Princeton professor of ecology and evolutionary biology and department chair. “This is a global theory that explains why biomes differ in nutrient conditions and in their abilities to respond to disturbances and to absorb carbon dioxide from the atmosphere.”  From: phys.org

GR:  This article by reputable scientists and published by a reputable journal troubles me. Thinking back to J.P. Grime’s book “Plant Strategies and Vegetation,” I wonder if the authors simply overlooked relevant literature when the proposed and then interpreted their research.  Adding more life-history variations to Grime’s work would be preferable to striking out on an independent course to rediscover Grime’s ideas. This interpretive remark by one of the authors is especially troubling:   “Tropical nitrogen-fixing plants are smart enough to know when to use costly nitrogen fixation to compete with neighboring plants, and when to turn it off, as if they are sentient beings,” Hedin said.

Frederick E. Clements had edged toward the idea that vegetation behaved as an organism as it matured. I believe H. A. Gleason demolished this idea quite well in his 1926 paper:  “The Individualistic Concept of the Plant Association” (Bulletin of the Torrey Botanical Club).