The Desert Flowers

 

Sonoaran Desert during the summer monsoon.  In the foreground is a low
growing Chollo cactus (Cylindropuntia sp.) backed by the spindly
Ocotillo (Fouquieria splendens) and numerous Saguaros (Carnegiea gigantea). 
Saguaro National Park, Arizona. 

Sonoaran Desert in the dry season.  Saguaro and
other desert plants show the effect of the lack on rain. 
Coronado National Forest, Arizona. 

The word desert conjurors up images of a sere landscape with scattered cacti and desiccated bushes.  For much of the year that description is accurate.  But sometimes, after a rain, the desert turns green and produces a riot of flowers. 

Sonoran Desert with a profusion of wildflowers including
Arizona Poppy (Kallstroemia grandiflora). 
Coronado National Forest, Arizona. 

In August, Diane and I visited the Sonoran and Chihuahuan deserts of Arizona.  When we told friends of our plans they looked at us like we were crazy.  They viewed going to the desert in August as bordering on reckless.  But late summer in Arizona is the monsoon season. Moist air streams north from the Pacific and Gulf of Mexico to drop over one third of the annual rainfall for the year during the summer months.  This rain causes a profusion of annual plants to germinate, flower and go to seed.  Perennial plants also flower with the summer abundance of water.  

Saguaros with arms, Ocotillo and Prickly Pear (Opuntia sp.)
Saguaro National Park, Arizona.

The Sonoran Desert is characterized by the iconic Saguaro Cactus (Carnegiea gigantea).  These giants reach heights of over 50 feet and may live hundreds of years.  A whole suite of other desert plants live among the Saguaros like Ocotillo, Acacias and many herbs. Desert plants often have spines to protect themselves and the water they contain from grazing animals.  Saguaros have vertical rows of spines and the trunk is pleated.  During dry times the circumference of the cactus decreases and pleats fold in.  When the rains come, the shallow root system takes up large amounts of water, the circumference increases and the pleats expand. 

 

A towering Saguaro cactus showing its pleats and rows of spines.
Saguaro National Park, Arizona.

Saguaro in flower with pollenating bees.
Saguaro National Park, Arizona.

Cactus Wrens (Campylorhyncus brunneicapillus) on top of a Saguaro. These
small birds live and nest on cacti, as their name suggests.
Maricopa County, Arizona.

The Chihuahuan Desert lies east of the Sonoran Desert and ranges from southeastern Arizona, southern New Mexico, west Texas and into the state of Chihuahua, Mexico.  This desert is generally at a higher altitude than the Sonoran Desert, with extensive grasslands and characteristic yuccas and agaves.   

Grassland in the transition zone between the
Sonoaran and Chichuahuan Deserts. This area was flush with green grass.
Las Cienegas National Conservation Area, Arizona.  

Soaptree Yucca (Yucca elata) flowering in the Sonoran Desert.
Portal, Arizona.

Yuccas and agaves are found throughout these deserts.  They are classified in the Asparagaceae along with that delicious food plant, asparagus. They have long leaves with spines along the leaf margins and a large spine on the tip.  Yuccas can flower many times but agaves flower once then die.  Agave americana, the Century Plant, is a native to the deserts of the American southwest and northern Mexico.  These plants can live for 20-30 years (not 100) and are the starting material for the alcoholic beverage mescal. A related species, A. tequilana, is used to make tequila. The last act in the life of a Century Plant is to send up a 30 foot flowering stalk with dozens of yellow flowers. These flowers are pollinated by bats, moths and hummingbirds.   

Century Plant (Agave americana).
This relative of lilies has large, pointed, succulent 
leaves.  It lives for 20 to 30 years (not 100) then sends
up a tall flowering stalk with yellow blooms. 
Portal, Arizona. 

Century Plant flowers.  
Saguaro National Park. 

Beside the majestic Saguaros there are many other cacti living in these deserts.  Some members of the cactus family, the Cactaceae, are cylindrical and others have flat pads.  The main body of a cactus is the stem which is photosynthetic with a thick waxy cuticle to retain water. The spines, for which cacti are famous, are modified leaves.  Cactus flowers come in many colors and are pollinated by insects, bats and birds.  

Brown-spined Prickly Pear (Opuntia phaeacantha) in flower.
Coronado National Forest, Arizona. 

Pincushion Cactus (Mammillaria grahamii) in flower.
Coronado National Forest, Arizona. 

Tree Chollo (Cylindropuntia imbricata) in flower. 
Saguaro National Park, Arizona. 

.

Wooden "skeleton" of Tree Chollo. 
The skeleton is the internal bracing that supports the plant. 
Saguaro National Park, Arizona. 

There are numerous shrubs and small trees in the desert and many flower during the rainy season. These plants produces leaves and flowers in response to rain. Most of these shrubby desert plants are protected by spines or thorns.

Ocotillo (Fouquieria splendens) branch with leaves. 
For much of the year Ocotillo looks like dead sticks.
Saguaro National Park, Arizona. 

Ocotillo with leaves and flowers. Although
they may look like it, Ocotillos are not cacti. 
Saguaro National Park, Arizona. 

Velvet Pod Mimosa (Mimosa dysocarpa). This member of the pea
family (Fabaceae) is a small tree with compound leaves, spines and pink flowers.
Coronado National Forest, Arizona. 

Sweet Acacia (Vachellia farnesiana) is another member of the Fabaceae.
The pods of this shrubby tree are sweet to the taste. 
Cochise County, Arizona. 

The non-native Bird of Paradise (Erythrostemon gilliesii) is yet
another member of the pea family.  The large blooms have
bright yellow petals and blazing red stamens. 
Portal, Arizona.  

Small perennial and annual herbs are well represented in the desert's flowering season. Some hug the ground, some are vines and ramble over other plants and some raise their flowers over the surrounding vegetation.  The growth of these plants cause an explosion in animal populations, particularly insects.  Many of the insects act as pollinators.  Insects are also hurrying through their reproductive cycles and need to make the next generation before the plants wither in the dry heat to come.  

Arizona Poppy (Kallstroemia grandiflora) puts on spectacular displays during
the monsoon.  It is not a true poppy and does not produce opium.
Coronado National Forest, Arizona. 

Prickly Poppy (Argemone pleiacantha) is a true poppy
but it does not produce opium. 
Coronado National Forest, Arizona. 

Rocky Mountain Bee Plant (Cleome serrulata) being pollinated
by Tarantula Hawks (Pepsis formosa). These large wasps lay their
eggs on tarantulas but the adults feed on nectar. This plant and insect are 
found throughout the desert southwest but these were seen at
Vermillion Cliffs National Monument, Arizona. 

Desert Marigold (Baileya multiradiata). These perennials are found throughout
the desert southwest and northern Mexico. 
Coronado National Forest, Arizona. 

Littleleaf Ratany (Krameria erecta). This interesting small shrub is a parasite,
drawing water and nutrients from the roots of nearby plants. 
It also actively carries out photosynthesis. 
Coronado National Forest, Arizona. 

Fruits of Clematis drummondii give this plant its 
common name, Old Man's Beard.  These fruits are
dispersed by the wind.
Patagonia Lake State Park, Arizona. 

Shrubby Purslane (Portulaca suffrutescens) is a perennial succulent with salmon colored flowers.
Coronado National Forest, Arizona. 

Punctureweed (Tribulus terrestris) is a low-growing
plants with yellow flowers.  The fruits have large spines and
any bicyclist who runs over this plant with have a flat tire.
Coronado National Forest, Arizona. 

Dakota Mock Vervain (Glandularia bipinnatifida) is a member
of the Verbena family and found throughout the west. 
Patagonia State Park, Arizona. 

Yellow-spined Thistle (Cirsium ochrocentrum)
in the sunflower family (Asteraceae), is well protected by prickly leaves
Coronado National Forest, Arizona. 

The desert flowers were a revelation.  These plants dash through their lifecycle in the summer rainy season in a race to reproduce before heat overtakes them. To see the the desert covered with bright green leaves and punctuated with brilliantly colored flowers gave us a whole new perspective on this ecosystem. 

The Lost Franklinia

 

Franklina alatamaha in flower.  
Rowan County, North Carolina.

The story starts with a father and son team of botanists in colonial America during the late 1700s.  The father, John Bartram, founded America’s first botanical garden just outside Philadelphia and undertook botanical explorations of the British colonies in North America.  John Bartram shared plants with many European scientists including the founder of modern biological classification, Carl Linnaeus.  He was appointed Royal Botanist in North America by King George III. The son, William Bartram was a botanist, ornithologist and natural history writer whose great work, Travels Through North & South Carolina, Georgia, East & West Florida, the Cherokee Country, the Extensive Territories of the Muscogulges or Creek Confederacy, and the Country of the Chactaws; Containing An Account of the Soil and Natural Productions of Those Regions, Together with Observations on the Manners of the Indians, or as it is commonly called, Bartram’s Travels, is still read today.

 

Franklina alatamaha lithograph from Bartram's Travels.
https://en.wikipedia.org/wiki/William_Bartram#/media/File:William_Bartram01.jpg

The Bartrams were making their first foray into the American south in 1765.  The father and son team was exploring the Altamaha River valley on the coastal plain of Georgia when they saw an odd, shrubby tree with white flowers. William Bartram returned to Georgia several times in the 1770s and found this plant growing only at this one location near Fort Barrington.  He was able to collect seeds from the shrub and return them to Philadelphia.  Bartram was not able to grow plants from the seeds he collected until after his father’s death, but these plants thrived in the botanical garden and flowered there.  After several name changes the plant became known as Franklina alatamaha to honor the Bartram's friend Benjamin Franklin and to commemorate the only location this plant was known to grow. The extra "a" in specific name for this plant reflects an alternative spelling of Altamaha that was current in the late 18^th century. 

Harper Lake just off the Altamaha River near Ft. Barrington.
McIntosh County, Georgia.

Franklin’s Tree, as it is commonly known, was seen growing in the wild along the Altamaha River during the late 1700s but the last know collection was made in 1803.  Franklinia was then extinct in the wild.  But Bartram shared seed and plants with many people and institutions and they shared and they shared.  Franklin’s Tree is now grown in botanical gardens, parks and yards throughout North America.  The cause of its extinction in the wild is a matter of debate.  First, the population of Franklinia alatamaha was already small when it was found by the Bartrams.  Perhaps it once had a wider distribution but in the late 1700s it was restricted to a small area thus limiting the number of plants.  Some scientists think the establishment of cotton plantations on the Coastal Plain of Georgia introduced a pathogen that reduced the already small population.  Others cite over-collection by botanists of the day.  Still others think a natural disaster like a flood of the Altamaha River eliminated the wild population. But whatever the reason, Franklinia was gone from its original habitat by the early 19th century.    

Franklinia alatamaha leaves and flower buds.
Rowan County, North Carolina. 

Franklinia alatamaha flower with Bumblebee (Bombus sp.) pollinators.
Rowan County, North Carolina. 

Franklinia is a member of the Tea Family, the Theaceae, that also contains Tea plants (Camellia sinensis), Flowering Camellias (Camellia sp.) and several American relatives including Loblolly Bay (Gordonia lasianthus).    

Loblolly Bay (Gordonia lasianthus) is in the same family as Franklinia.
The relationship between these plants is made clear by the flower structure.
Rowan County, North Carolina. 

One summer day I set out to find the original location of the lost Franklinia.  I left Atlanta just after dawn, hoping to arrive at Fort Barrington before the day got too hot.  Interstate driving made the first part of the trip go quickly.  Then on to a US highway with numerous small towns.  Then off the highway on a paved road, then a gravel road, then a road of fine white sand.  The further I went, the wilder the country became.  There were farms and paper company land with pine plantations interspersed with clear cuts.  One mile from Fort Barrington a sign next to the road proclaimed, “Private Property, No Trespassing”.  That brought my progress to a halt in a cloud of dust on the white sand road.  It seems Fort Barrington is now a private hunt camp and Bartram chasers are not welcome.  I backtracked a little and found a road called Barrington Park Road.  That sounded promising and it led to Barrington County Park, with its campground on Harper Lake, just off the Altamaha River.  

Live Oak (Quercus virginiana) hammock.
Barrington County Park, McIntosh County, Georgia.

Long Leaf Pine (Pinus palustris) savanna.
McIntosh County, Georgia.

Buttonbush (Cephalanthus occidentalis) flowering on Harper Lake.
McIntosh County, Georgia. 

As I walked around the park the heat was building.  I found Bald Cypress along the river and on higher ground Live Oak (Quercus virginiana) hammocks.  There were Long Leaf Pines (Pinus palustris) and Saw Palmettos (Serenoa repens).  There I could picture the Bartrams, walking these same woods and coming on one of the rarest plants in America.  A plant so rare that in a few decades it would be lost in the wild and exist only in gardens.  Franklinia alatamaha survives today through the extraordinary efforts of John and William Bartram.  They collected and propagated this rare plant and saved it for the world.

Arizona Reptiles

A coiled Western Diamondback Rattlesnake (Crotalus atrox)
showing its forked tongue.
Portal, Arizona. Photo courtesy of Matt McCluskey.

On a recent trip to Arizona, Diane and I got to see some fantastic reptiles.  We were with a group visiting the great birding spots in southeastern Arizona and western New Mexico.  While we were looking at birds these cold-blooded creatures kept popping up.

Desert Box Turtle (Terrapene ornata luteola).
Cochise County Arizona.

A Desert Box Turtle (Terrapene ornata luteola) was dashing across a gravel road near the settlement of Portal, Arizona in the Chihuahuan Desert. The Desert Box Turtle is a relative of the Common Box Turtle (Terapenne carolina) that we often see in North Carolina.  Both these turtles have a domed top shell, a hinged bottom shell and fierce yellow-orange eyes.  The coloring of the shell of Desert Box Turtles is more muted than that of the Common Box Turtle so it blends in with its desert environment. We piled out of the van, had a good look at the turtle and than moved it across the road.  The Desert Box Turtle faces a number of threats including habitat loss and over-collection for the pet trade.  It was a pleasure to see this turtle walk away from us and out into the desert.

 

Desert Tortoise (Gopherus morafkai).
Pima County Arizona.

Another turtle of the desert we saw was the Sonoran Desert Tortoise (Gopherus morafkai).  This tortoise also has an eastern counterpart, the Gopher Tortoise (Gopherus polyphemus) of the southeastern United States.  The Sonoran Desert Tortoise has a high domed shell and what is described as elephantine legs.  Their front legs are large and clawed and are used to dig burrows where they can shelter from the heat. Tortoise burrows are shared by a wide variety of other reptiles, birds, mammals and invertebrates.  Sonoran Desert Tortoises get most of their water from their diet of plants and are most active during the monsoon season in late summer. 

Sonoran Spiny-tailed Iguana (Ctenosaura macrolopha).
Arizona-Sonoran Desert Museum, Arizona. 

Lizards were abundant in the desert.  At the famed Arizona-Sonoran Desert Museum, they have a population of large lizards called Sonoran Spiny-tailed Iguanas (Ctenosaura macrolopha).  This lizard is native to the Sonoran Desert in Mexico and has become established at the Museum.  

Common Chuckwalla (Sauromalus ater). 
Chiricahua Desert Museum, New Mexico.

We saw two other large lizards outside their natural range at the Chiricahua Desert Museum in Rodeo, New Mexico.  A Common Chuckwalla (Sauromalus ater) was basking on a boulder in the outdoor exhibits of the Museum. This hulking reptile has wrinkled skin and a blunt tail.  The normal range for the Common Chuckwalla is northwestern Mexico, western Arizona, southeastern California and southern Nevada.  

Desert Iguana (Dipsosaurus dorsalis). 
Chiricahua Desert Museum. New Mexico. 

A second lizard at the Chiricahua Desert Museum was the Desert Iguana (Dipsosaurus dorsalis).  This iguana is as lithe as the Chuckwalla is chunky.  Its range is similar to that of the Common Chuckwalla so it was out of its range in the Chihuahuan desert. The Desert Iguana has a blunt face, spots on the body and rings on its long tail.  

Sonoran Spotted Whiptail (Aspidocelis sonorae).
Santa Cruz County, Arizona. 

Whiptails were the most common lizards we encountered.  A few inches long, they would race across trails and disappear in the brush.  We found a Sonoran Spotted Whiptail (Aspidoscelis sonorae) in the foothills of the Santa Rita Mountains, part of the Sonoran Desert.     

Clark's Spiny Lizard (Scleroporus clarkii).
Patagonia Lake State Park, Arizona. 

The most spectacular lizard we found was on the shores of Patagonia Lake, Arizona.  This man-made lake was formed by damming Sonoita Creek and is a magnet for wildlife.  A male Clark’s Spiny Lizard (Scleroporus clarkii) was walking along a dead willow branch.  He was trying to attract a mate by showing his iridescent blue belly and throat while doing pushups.  We never saw if he attracted a female but he sure caught our attention.

Elegant Earless Lizard (Holbrookia elegans). 
Patagonia Lake State Park, Arizona.

Another beautiful lizard from Patagonia Lake was the Elegant Earless Lizard (Holbrookia elegans).  As its name suggests this small lizard has no visible ear openings.  This male has bold orange and yellow markings on the side and chevron-shaped markings on the back.  

Some members of our group went out at night looking for rattlesnakes. They found several Western Diamondbacks (Crotalus atrox), a venomous snake that can reach five feet in length.  These impressive snakes hunt small mammals and were easily seen crossing the road.  Western Diamondbacks have large triangular heads that contain heat sensing organs they use to track their warm-blooded prey.  They have black, forked tongues they use to sense chemicals in their environment.  The defining characteristic of rattlesnakes is their rattle.  The rattle is made of keratin, the same protein that makes up the snake's scales.  Rattlesnakes shake their rattle to warn potential predators of their presence. Above the rattle the snake has several black and white bands on the tail.

Western Diamondback showing its large triangular head,
ringed tail and rattle.
Portal, Arizona. Photo courtesy of Matt McCluskey.

We had an outstanding snake encounter in Sabino Canyon near Tucson.  This recreation area is popular with hikers and families.  Just after sunrise, while we were walking among the cactus and acacia, we spotted a Western Patch-nosed Snake (Salvadora hexalepis) crawling down a burrow.  Nearby a Desert Kingsnake (Lampropetlis splendida) was coiled under a mesquite tree.  A half an hour later we passed the same spot again and the kingsnake and patch-nosed snake were locked in mortal combat.  The kingsnake was constricting the patch-nosed snake then the kingsnake began to consume the patch-nosed snake tail first.  The patch-nosed snake pulled its head from the burrow and the kingsnake began to eat it head first.  We left before the kingsnake had fully ingested the patch-nosed snake, but that single meal might last the kingsnake for several months.  

Western Patch-nosed Snake (Salvadora lexalepis) entering a burrow. 
Sabino Canyon, Coronado National Forest, Arizona.

Desert Kingsnake (Lamproetlis splendida)
pulling the Western Patch-nosed Snake from a burrow.
Sabino Canyon, Coronado National Forest, Arizona.

The heads of both the Western Patch-nosed Snake and Desert Kingsnake 
are visible as the kingsnake constricts the patch-nosed snake. 
Sabino Canyon, Coronado National Forest, Arizona. 

Reptile diversity is high in the desert and we were privileged to see a generous slice during our travels. While some of these creatures are feared and even hated they are fascinating and essential components of the desert ecosystem. 

 

 

Sea Oats, River Oats

 

Uniola paniculata, Sea Oats grow on the dunes
of the Southeastern United States.
Huntington Beach State Park, South Carolina. 

Sea Oats (Uniola paniculata) are spectacular plants of beach dunes in the Southeast.  These grasses can grow to six feet in height and thrive is harsh conditions of sunlight, heat, salt and drought.  The only source of fresh water for Sea Oats is rain and because of the sandy soil of their dune habitat that water drains quickly.  Sea Oats will not wilt until soil moisture reaches about 1% but recover quickly when water returns.  Too much water is harmful to Sea Oats.  If roots are waterlogged, even for a few days will cause the plant to die.  Sea Oats have extensive root systems and they are important plants in stabilizing dunes. The flowers of Sea Oats are born in flat structures called spikelets.  The spikelets give the plant their name because they resemble those made by oats.  Fruits mature in the spikelets and the seeds are carried away on the wind.  Marsh Rabbits (Sylvilagus palustris) that inhabit the dunes eat the fruits. Sea Oats are also a major food source for the Perdido Key Beach Mouse (Peromyscus polionotus trissyllepsis).  This federally endangered rodent is found only on Perdido Key in the panhandle of Florida where Sea Oats are abundant.  Sparrows and Red-winged Blackbirds (Agelaius phoeniecus) are also major consumers of Sea Oats.  

Sea Oats plant with mature fruits.
Palm Beach County, Florida.

Sea Oat fruits.
Palm Beach County, Florida.

River Oats (Chasmanthium latifolium) resemble Sea Oats.  River Oats are grasses that reach 3-4 feet and make oat-like spikelets bearing flowers.  As their name suggests, River Oats grow along river banks often in the riparian forest understory.  River Oats are very shade tolerant and are popular for landscaping shady areas.  River Oats are found from New York to Florida, from the Midwest to Texas and south into Mexico.   River Oats were once classified in the same genus as Sea Oats and the resemblance is striking, but are now recognized as distinct genus.  Many animals including; White-tailed Deer (Odocoileus virginianus), Northern Bobwhite (Colinus virginianus) and the larvae of several moths and butterflies consume River Oat fruits and leaves.   

River Oats (Chasmanthium latifolium) growing beside a creek.
Rowan County, North Carolina.

River Oat flowers.
Rowan County, North Carolina. 

Sea oats stand as sentinels on the dunes, protecting the shoreline.  They are often planted during beach restoration and are protected by law in many southeastern states.   While Sea Oats are on the front line of erosion control, River Oats grow in creek-side forests, their seed heads nodding as they watch the river flow.

River Oats.
Rowan County, North Carolina.

Why is a Flower Bed Like a Pandemic?

 

Pink Evening Primrose (Oenothera speciosa) flower.
Rowan County, North Carolina.

We have a small flower bed at the corner of our garage.  It is entirely enclosed by the driveway, a curving sidewalk and the garage.  In fall we plant pansies (Viola sp.) that flower through the winter and spring.  In spring, Pink Evening Primrose, Oenothera speciosa puts on a flowering show.  Early summer brings Bee Balm (Monarda didyma) with its purple flowers and the red, pink and white blooms of the exotic Impatiens balsamina.   So, this small flower bed blooms throughout the year.

 

Our flower bed with Pink Evening Primrose and Pansies. in flower.
Rowan County, North Carolina.

  

Time lapse video of Primrose flowers, mid-April to mid-June

Rowan County, North Carolina. 

I have always been impressed at how the number of Pink Evening Primrose flowers increase, reach a peak then fall off.  This spring I counted the Primrose flowers and photographed the bed nearly every day for almost two months.  By the middle of June, the blooms were tailing off and I graphed the number of flowers for each day. 

 

Graph of Pink Evening Primrose flowers per day 
from mid-April to mid-June.

The graph shows a rapid increase in the number of flowers with the peak flower number coming in the middle of May.  Around the peak, more than 300 flowers were open each day in this small bed.  The number of flowers started a gradual decrease as we got into June.  Flower numbers fluctuated from day-to-day after the peak. This was probably because of the natural variation in flower bud production by the Primrose and may have also been influenced by environmental factors like day length and rain fall.

I was struck by how this graph of flower numbers over time resembled the pattern of cases in an epidemic.  When a new disease enters a human population the number of cases rapidly increases.  The rate of increase depends on many factors like transmissibility of the infectious agent, the density of the human population and preventative measures. The numbers eventually reach a maximum then decline. 

Idealized graph of an epidemic.  
https://www2.palomar.edu/anthro/medical/med_3.htm

The ongoing COVID-19 tragedy is a more complicated situation.  A pandemic is a world-wide, long-term epidemic.  COVID-19 started in China in late 2019 and reached the United States and many other countries in the winter of 2020.  By March 2020, US case numbers began to increase.  The case numbers peaked in April and began a gradual decline as preventative measures like closing locations where people congregate, working from home and mask wearing was required.  During the summer of 2020 cases began to increase again as people traveled for business and pleasure.  The numbers began to decline again in late summer but as the weather cooled, people gathered inside and traveled for the holidays.  This caused another spike in the number of COVID-19 cases that reached their peak in January 2021.  Two vaccines were released to the American public in early 2021 and the number of COVID-19 cases began to rapidly decline.  This decrease has continued into the summer of 2021.

Number of COVID-19 cases in the United States, February 2020-June 2021.
New York Times. 

Both Primrose flowers and COVID-19 cases showed a similar pattern. Pink Evening Primroses in the flower bed next to our garage had a rapid increase in number, peaked, then as the days got longer flower production tapered off.  The United States population has suffered through several peaks of COVID-19.  Millions were sickened, hundreds of thousands died and while the virus is still circulating, it is now on the decline.  This welcome decrease in cases was caused by a massive public health response, natural immunity in recovered COVID-19 patients and the vaccination of millions of susceptible people. In many countries the pandemic continues to rage as their people await effective public health responses.  

So, why is a flower bed like a pandemic?  Well, it is not, except in a superficial way.  The dynamics of biological systems allow for exponential growth.  At some point, the growth is limited by intrinsic or environmental factors and the numbers decline. The real connection is that both the virus and the flower are governed by similar biological laws.  

Flying Seeds

 

Goat's Beard (Tragopogon dubius) head with many fruits. 

These flying fruits disperse seeds over long distances.  

Rowan County, North Carolina. 

 

Plants disperse their seeds in many ways. Seed dispersal is vital for plants to colonize new areas and so new plants are not in direct competition with their parent.  In flowering plants, the seed is part of the fruit, and the main function of the fruit is dispersal of seeds. Some seeds are wrapped in a tasty fruit and are carried away by animals and deposited in new locations.  Other fruits are hitchhikers that cling to the fur of animals or the bootlaces of unsuspecting hikers.  Still others have buoyant fruits and float away on ocean currents.  And some fruits fly.  

Fruits of Box Elder (Acer negundo). Like all
maples, Box Elder makes winged fruits called samaras. 
Rowan County, North Carolina. 

A single samara of Box Elder.  The seed is at 
the bottom and the wing is at the top of the picture.
Rowan County, North Carolina. 

Slow-motion video of Red Maple (Acer rubrum) flying samaras.

Rowan County, North Carolina. 

Flying seeds have two main strategies for dispersal, wings or parachutes.  Maples (Acer sp.) make a fruit called a samara with the seed at the end of a single, asymmetrical wing. When the fruit falls from a maple tree it helicopters down and on a breezy day it can travel long distances.  The wings of maple samaras are airfoils like those of airplanes.  The wing shape produces lift and allows the seed to remain aloft for a long time.

Winged seed of Loblolly Pine (Pinus taeda).
Rowan County, North Carolina. 

Pines (Pinus sp.) do not make fruits since they are Gymnosperms.  Gymnosperms have naked seeds borne on cones and are not part of fruits.  Pine seeds are very similar in appearance to maple fruits and fly in a similar manner.  Ash trees (Fraxinus sp.) also make samaras.  Ash fruits have a seed and an airfoil wing and they too are good flyers.  Long distance dispersal means these trees are often the first to colonize new open areas.  

Samaras of American Ash (Fraxinus americana).
Rowan County, North Carolina. 

Close-up of an American Ash samara.
Rowan County, North Carolina. 

Parachute fruits are made by some members of the sunflower family, the Asteraceae.  The best known of these is the Common Dandelion (Taraxicum officinale).  Everyone has picked a fruiting head of Dandelion and blown the fruits into the wind.  Dandelions are natives of Eurasia and have spread themselves across North America by means of these flying seeds.  Another member of the sunflower family that makes these flying fruits is Goat’s Beard (Tragopogon dubius).  This introduction from Europe is much taller than the Common Dandelion and makes large fruiting heads with abundant flying seeds.  The fruits of both these plants are called achenes.  They have the seed at the bottom, a stalk called the beak and fine cellulose fibers at the top, the pappus.  The pappus acts as the parachute and allows the fruit to travel long distances. 

Fruiting head of Common Dandelion (Taraxicum officinale).  Each achene
is made up of a seed, beak and pappus.
Rowan County, North Carolina.

 

Close up of a Common Dandelion achene.  The seed is at the bottom,
the pappus is at the top and they are connected by the beak.  
Rowan County, North Carolina. 

Bull Thistle (Cirsium vulgare) is yet another Asteraceae with parachuting fruits.  Bull Thistle grows to several feet in height, has spiky leaves and makes purple flowers.  Unlike Common Dandelion, Bull Thistle fruits lack a beak but fly just as well. 

Bull Thistle (Cirsium vulgare) leaves.
Rowan County, North Carolina.

Bull Thistle flower.
Rowan County, North Carolina.

Bull Thistle achene being released from a fruiting head.
Rowan County, North Carolina. 

Video of Bull Thistle achenes flying from a mature flower.

Rowan County, North Carolina.

On windy spring days the air can be filled with flying maple samaras or a summer walk through a meadow can bring clouds of parachute borne seeds of Dandelions.  All these seeds are trying for the same thing.  A fresh start for the plant in a new place.