Wildflower or Weed?

 

Bird's Eye Speedwell (Veronica persica). A small, early spring 
wildflower from our yard.  Rowan County, North Carolina. 

Spring is upon us and in our yard delicate wildflowers are popping up and blooming.  Our lawn is not a smooth monoculture of Bermuda grass. The lawn does have some grass but it also has lots of wildflowers, that is weeds. A definition of a weed is "a plant that is growing where someone does not want it".  Lots of plants that we call weeds are adapted to living in disturbed habitats. Our lawns and roadsides mimic the natural environment where these plants thrive.   

Flowers and fruits of Cardamine hirsuta, Hairy Bittercress.
Rowan County, North Carolina.

An early and dainty wildflower is Cardamine hirsuta, Hairy Bittercress.  This small plant has flowers with flower parts in fours including its white petals.  The fruits of Hairy Bittercress, called siliques, are cylindrical and contain a single row of tiny seeds.  Cardamine hirsuta is in the family Brassicaceae, a group that includes many important vegetables including mustard, cabbage, broccoli and turnips.  Hairy Bittercress is native to Europe and has spread around the world, including much of the United States.   

 

Flowers of Hairy Bittercress with their four 
petaled flowers.  Rowan County, North Carolina.

Two other early lawn weeds are in the mint family, the Lamiaceae.  Lamium purpureum (Red-dead Nettle) and Lamium amplexicaule (Henbit) are both small herbaceous plants that make hooded, purple flowers.  Lamium flowers are bee pollinated and provide nectar for the early emerging insects.  The common name, Red-dead Nettle, refers to the superficial resemblance of Lamium purpureum to true nettles in the genus Utrica.  However, Lamium purpureum does not sting, hence the name dead-nettle.   Both these species of Lamium are found throughout North America but originated in Eurasia. 

 

The mint Lamium purpureum or Red-dead Nettle.
Rowan County, North Carolina. 

A large stand of Henbit, Lamium amplexicaule.
Rowan County, North Carolina. 

Our yard is graced by two species of Veronica in early spring.  The common name of Veronica is Speedwell and they are classified in the plantain family, the Plantaginaceae.  Veronica hederifolia, Ivy-leafed Speedwell is a small plant with tiny blue flowers.  Veronica persica, Bird’s-eye Speedwell, flowers are a little larger than the Ivy-leafed Speedwell and are also blue.  Both these Speedwells have darker blue lines on the petals called nectar guides.  Insect pollinators like bees can see ultraviolet and these lines are dark ultraviolet arrows pointing to the flower’s nectary.  As the bee is sipping nectar it picks up pollen and takes it to the next Veronica flower.  Both Speedwells were introduced to North America from Eurasia. 

Ivy-leafed Speedwell, Veronica hederifolia.
Rowan County, North Carolina.

 

Veronica persica, Bird's-Eye Speedwell. This species has
larger flowers than the Ivy-leafed Speedwell. 
Rowan County, North Carolina.

The white flowers of Common Chickweed (Stellaria media) also appear in spring.  Common Chickweed flowers have five petals but because each petal is two-lobed the flowers appear to have ten petals.  Stellaria media is in the Caryophyllaceae, the same family as carnations.  Chickweed is native to Asia and Europe and can be eaten raw in salads or cooked like spinach. 

 

Common Chickweed, Stellaria media, with its tiny white flowers.
Rowan County, North Carolina.

Sow Thistle, Sonchus oleraceus, like our native thistles, is classified in the Asteraceae, the sunflower family.  It is yet another spring weed that was introduced from Eurasia.  Sow Thistle grows in disturbed habitats. This plant is highly nutritious and eaten by people and pigs alike.  The flowers of Sow Thistle are yellow and resemble those of Dandelion (Taraxacum officinale).  The fruits of Sow Thistle are also like those of Dandelion and are dispersed on the wind. 

 

Sonchus oleraceus, Sow Thistle growing beside a road
in my neighborhood.  This member of the sunflower family is 
originally from Eurasia.  Rowan County, North Carolina. 

Close up of flowers and fruits of Sow Thistle.  The fruits of this plant can fly on the breeze. 
Rowan County, North Carolina. 

Azure Bluet (Houstonia caerulea) has delicate blue flowers with four petals and a yellow center.  Houstonia caerulea is a member of the Rubiaceae, a family that also contains the plants that give us coffee beans and quinine.  Unlike the other wildflowers already discussed in this blog, Azure Bluets are native to North American being found from Eastern Canada to the southern US.  

Azure Bluet, Houstonia caerulea growing in a lawn. 
Rowan County, North Carolina. 

A whole segment of the chemical industry is devoted to developing and selling weed killers.  We never apply them to our “lawn”.  After all, our yard is mostly weeds, or wildflowers.

Monarchs, Viceroys and Queens

 

A Monarch Butterfly (Danaus plexippus) feeding on 
Tropical Milkweed (Asclepias curassavica).
Rowan County, North Carolina.

I know, I know, another story about Monarch Butterflies.  I can’t help it.  Monarchs (Danaus plexippus) are large, brilliantly colored, poisonous and make an epic migration every year. Monarchs also belong to a mimicry complex, a group of butterflies that resemble each other.  This resemblance protects them from predators.  Monarchs are distasteful to birds because their larvae develop on milkweeds (Asclepias sp.).  Milkweeds make toxic compounds called cardiac glycosides that repel most insects but the Monarch larvae have evolved tolerance to these chemicals.  When a Monarch larva metamorphoses into the adult butterfly it retains the toxic plant compounds to repel birds. 

 

Monarch Butterflies migrating through the Black Mountain Gap below
Mount Mitchell, North Carolina.  These Monarchs were feeding on Aster sp. 
on their way to Mexico.  Yancy County, North Carolina.

Viceroys (Limenitis archippus) and Queens (Danaus gilippus) both bear a remarkable resemblance to Monarchs with their bright orange wings, striped with black and dotted with white.  Monarchs are found throughout North America and into Mexico.  Viceroys live in the eastern two thirds of North America and Mexico.  Queens have a more southern distribution along the southern border states of the US from Florida to California and into Mexico. 

 

A Viceroy Butterfly (Limenitis archippus) resting on a Tag Alder
(Ulnus serrulata). Viceroys and Monarchs are members of a mimicry complex.
Clayton County, Georgia.

The standard story of mimicry in these butterflies has the Monarchs being protected from bird predators by toxic cardiac glycosides.  Viceroys were supposed to be palatable to birds and avoid being eaten because of their resemblance to Monarchs even though they don't have chemical protection.  This type of mimicry, with a toxic model (Monarch) and a tasty mimic (Viceroy) is called Batesian mimicry.  Henry Walter Bates, a 19^th Century English naturalist who is the namesake for this mimicry, first described this relationship based on his study of South American butterflies. 

Recently researchers have shown the Monarch-Viceroy mimicry story is more complicated than originally thought.  Viceroy butterfly larvae often develop on willow (Salix sp.) leaves and can also be poisonous.  Willows contain toxic salicylic compounds related to aspirin.  The Viceroy caterpillars ingest these molecules and the adult butterflies may be unpalatable to birds.  Mimicry where two protected species resemble each other is called Müllerian mimicry, named for German zoologist Johann Müller.   Müller, like Bates, studied butterflies in South American in the 1800s and discovered this distinctive type of mimicry.  In Müllerian mimicry several protected species resemble each other and all are protected from predators.  Müllerian mimicry is why bees, wasps, yellow jackets and hornets all resemble each other. The yellow and black bodies of these insects send a clear message to leave us alone.  Monarchs and Viceroys (sometimes) are both chemically protected so their resemblance can be Müllerian mimicry.  

 

A Queen (Danaus gilippus) feeding on Oakleaf Fleabane (Erigeron quercifolius).
This butterfly is also a member of the mimicry complex with Monarchs and Viceroys.
Palm Beach County, Florida.  

Queens are closely related to Monarchs and their larvae develop on milkweeds and their relatives.  Queens are protected by the same cardiac glycosides found in Monarchs.  Viceroys were once thought to be Batesian mimics of Queens where their ranges overlap.  But since we now know Viceroys are chemically protected this is another example of Müllerian mimicry.   The Viceroy-Queen story in Florida is even more complicated.  In 2019 a group of American researchers found that in north Florida the Viceroy population is high and the Queen population is low.  There the Viceroys have a higher concentration of chemical defense compounds.  In south Florida Queens are abundant and Viceroys are rare and are not well protected.  But in central Florida both species are relatively abundant and the Viceroys have low concentrations of their protective chemicals.  With lots of Queens around, the Viceroys do not need as much of the toxic chemicals.  So, in central Florida, the Viceroy-Queen relationship changes from Müllerian to Batesian mimicry.  

 

A Monarch on Tropical Milkweed. 
Rowan County, North Carolina.

The work of both Bates and Müller on mimicry gave early, independent evidence for Darwin and Wallace’s theory of Natural Selection. This mimicry is on display for us to see in these brilliant butterflies.