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)


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.)

Species Introductions Are Accelerating

GR:  Invasive plants and animals are destroying native ecosystems. Some species that we take from their homes and release in other regions explode across the new habitat. Free from their natural competitors and diseases, the species are like Superman freed from Krypton’s light. Local species cannot compete and are replaced.  I’ve studied some of the plant species that do this. You can read what I’ve learned here.

My work focuses on invasive plants, but animals can be equally destructive. The Eurasian Wild Boar is a good example of the hundreds of species impacting North American ecosystems. Here’s a brief review of the history of its introduction and spread in the U. S.

Feral Eurasian Wild Boar

Feral Eurasian Wild Boar

Invasive species are second only to complete habitat destruction by roads and buildings as destroyers of nature. Global warming will take their place over the next few decades, but that doesn’t mean that we can ignore invasives. Protecting nature requires that we tend to all our destructive behaviors. My articles include suggestions and references to other resources for invasive plant control.

The article below from the National Geographic Society Blog reports that the invasive species problem is growing. Humans really began spreading species 500 years ago when they began crossing the oceans. It surprises me that we’ve left anything behind, but apparently we left enough invasive species behind to continue and even accelerate this form of the human impact.

“A study released this month has illustrated that the rate of species introductions to locations outside their native range is increasing faster than ever. Hanno Seebens and many others used the date of first records of introductions to plot the total number of new non-native species records every year since 1500. They show that this is not only increasing, but accelerating, with no signs of saturation. The increase was particularly marked since the 1800s. This global exchange of species is not good news, as although it increases species richness at the regional scale, globally the species richness of our planet declines as species go extinct.

Global temporal trends in first record rates (dots) for all species (a) and taxonomic groups (b–q) (Source: Nature Communications)

“New Zealand was singled out as one country whose trend was negative compared to the rest of the world. As any traveller to New Zealand will have encountered, the biosecurity importation laws and policing are rigorous and every passenger is screened. In tandem with a ‘white-list’, where only certain non-native species are automatically permitted entry, and all others must be assessed, has clearly assisted in protecting New Zealand’s biodiversity and primary industries from the global trend in accelerating species introductions.” –James Russell (Continue reading:  Species Introductions Accelerating – National Geographic Society (blogs).)

Behind New Zealand’s wild plan to purge all pests

Invasive Species

GR:  After 1500 AD, sailing ships and then later on, motor-powered ships began transporting and introducing plant and animal species all over the globe. Freed from the predators and diseases of their homes, some of the introduced species became invasive–that is, they began spreading, replacing native species, and decreasing ecosystem stability and productive. This is not news, of course, biologists have long been aware of the devastation caused by invasive species.

Eradicating invasive species is very expensive and very difficult. National resolve and full public support are required. Eradication is something that we humans, who are responsible for spreading the invasive species, should be about everywhere.

However, it is essential to place greater focus preventing the initial introduction of non-native species. Prevention is cheaper and kinder than eradication. And again, prevention is not a new idea. Natural resource managers have known how to prevent invasions for the past century. In many instances, they just don’t take the necessary steps. Here are some articles on invasive plants.

New Zealand has one of the worst invasive plant and animal problems in the world. The article below describes an ambitious and necessary plan to do something about it.

New Zealand Eradication Plan

New Zealand has three invasive species of rat. The Pacific rat, or kiore (Rattus exulans), was introduced from Polynesia in about the twelfth century; the ship rat (Rattus rattus) arrived in the late 1700s; and the Norway rat (Rattus norvegicus) became established in the 1860s. All three prey on native birds, insects and lizards, and have been blamed for the decline or extinction of a variety of species.

“Razza the rat nearly ended James Russell’s scientific career. Twelve years ago, as an ecology graduate student, Russell was releasing radio-collared rats on to small islands off the coast of New Zealand to study how the creatures take hold and become invasive. Despite his sworn assurances that released animals would be well monitored and quickly removed, one rat, Razza, evaded capture and swam to a nearby island.

“For 18 weeks, Russell hunted the animal. Frustrated and embarrassed, he fretted about how the disaster would affect his PhD. “I felt rather morose about the prospects for my dissertation,” he says.

“Although there was a lot of literature on controlling large rat populations, little had been written about tracking and killing a single rodent, which turns out to be rather important in efforts to completely eradicate a species. “It demonstrated how hard it is to catch that very first rat as it arrives on an island — or, conversely, the very last rat that you’re trying to get off,” says Russell, now at the University of Auckland.

Brushtail possums are among the numerous invasive pests regularly culled in New Zealand.

“Razza’s escape became the subject of a paper in Nature1 as well as a popular children’s book. And now, with more than a decade of successful pest-eradication projects behind him, Russell is taking on a much bigger challenge. He is coordinating research and development for a programme that the government announced last July to eliminate all invasive vertebrate predators — rats, brushtail possums, stoats and more — from New Zealand by 2050 to protect the country’s rare endemic species.” –Brian Owens (Continue reading:  Behind New Zealand’s wild plan to purge all pests : Nature News & Comment)