Duckweed Arrives

 

Duckweed (Lemna minor).
Catawba College Ecological Preserve.
Salisbury, North Carolina. 

The Emerald Ash Borer (Agrilus planipennis) has hit our area hard.  The swamp forest of the Catawba College Ecological Preserve in Salisbury, North Carolina has lost almost all its White Ash (Fraxinus amercana) trees to this invasive insect.  Emerald Ash Borers are small beetles that burrow into the trunks and kill the mature trees.   This massive die off of large trees has changed the nature of the swamp.  Where once a solid canopy of leaves shaded the swamp, now sunlight floods in.  Herbs, shrubs and trees are growing, and tiny floating plants are thriving between the trunks of the dead ash trees. 

 

Swamp forest with floating plants and dead
White Ash trees (Fraxinus americana) .
Catawba College Ecological Preserve.
Salisbury, North Carolina. 

Galleries dug by Emerald Ash Borers (Argrilis planipennis)
in a dead White Ash tree.
Catawba College Ecological Preserve,
Salisbury, North Carolina. 

Dead White Ash trees and the open canopy.
Catawba College Ecological Preserve.
Salisbury, North Carolina. 

Duckweed (Lemna  minor) is one of these small plants.  It is among the smallest of flowering plants with leaves just a few millimeters long. Each plant bears a single root that grows straight down in the water.  They carry out their whole life cycle floating on the surface of still, fresh water.  Duckweed is classified in the family Araceae, a group that also contains Philodendron and Jack-in-the Pulpit (Arisaema triphyllum).  Lemna minor is found on all continents except Antarctica with the Australian population consisting of introduced plants. 

Duckweed with its roots hanging in the water.
Catawba College Ecological Preserve.
Salisbury, North Carolina. 

Male Mallard (Anas platyrhynchos) with Duckweed.
Mecklenburg County, North Carolina. 

Three Duckweed plants on my
 fingertip each with a single root.
Catawba College Ecological Preserve,
Salisbury, North Carolina.  

While Duckweed is a flowering plant, but it rarely flowers.  Plants grow and divide asexually. It is carried to new habitats as whole plants by birds, often clinging to the feet or feathers of their namesake ducks.  Ducks are probably how Duckweed was introduced to the Catawba College Ecological Preserve swamp.  

Greater Duckweed (Spirodela polyrhiza) with the
smaller Lemna minor.
Catawba College Ecological Preserve.
Salisbury, North Carolina. 

Greater Duckweed on my
fingertip showing multiple roots. 
Catawba College Ecological Preserve, 
Salisbury, North Carolina. 

Another floating plant in the swamp is Greater Duckweed (Spirodela polyrhiza).  Its leaves are larger than Lemna minor and each plant has multiple roots.  Greater Duckweed is common in the northern hemisphere worldwide but is rarer in the southern hemisphere.  

People have found many uses for Duckweed.  It is used as a fertilizer, as a high protein animal feed and in wastewater treatment.   Duckweed is also highly efficient at removing and concentrating toxic metals from water.     

Carolina Mosquito Fern (Azolla cristata) and Duckweed.
Catawba College Ecological Preserve.
Salisbury, North Carolina. 

Another small floating plant that is now common in the swamp is the fern Azolla cristata or Carolina Mosquito Fern.  These tiny ferns have fronds that are covered with fine hairs that give them a velvety appearance.  The fronds may be green but can turn red in winter. The roots of Carolina Mosquito Fern harbor a symbiotic cyanobacterium Trichomus azollae.  This photosynthetic bacterium fixes nitrogen and supplies some of the organic nitrogen to the fern.  Because of its high nitrogen content some species of Azolla are used as biofertilizers.  

Duckweed and Greater Duckweed.
Catawba College Ecological Preserve.
Salisbury, North Carolina. 

It was tragic for this swamp to lose one of its predominant trees to an invasive insect.  But my friend, Dr. Jay Bolin has studied the effect of Emerald Ash Borers on the White Ash trees.  He says “There are winners and losers in any ecological change”.  The losers are clearly the ash trees and the winners are the the tiny aquatic plants that are thriving in the newly illuminated understory of the swamp.  

The Ancient Caledonia Forest

 

Scots Pine (Pinus sylvestris) in the
Ancient Caledonian Forest.
Loch Garten Nature Reserve, Scotland. 

The forests of Scotland are wreathed in myth and mystery.  The Romans built Hadrian’s Wall to protect Britannia from the wild Picts lurking in trees to the north.  Shakespeare’s Macbeth was certain of his rule until Birnam Wood marched on Dunsinane.   Robert Kirk, a 17^th century Scottish minister and folklorist, wrote of a Secret Commonwealth of elves, fauns and fairies that inhabited the Highland forests. 

Video of the Ancient Caledonian Forest.

Loch Garten Nature Reserve, Scotland. 

One of these Scottish woodlands is the Ancient Caledonian Forest.  It once covered much of Northern Scotland and was called the Great Wood.  The Ancient Caledonian Forest’s signature tree is the Scots Pine (Pinus sylvestris).  This tree and other species that populate this forest colonized the Highlands after the last ice age and comprise a unique assemblage of plants and animals.  We were able to hike in the Ancient Caledonia Forest during our recent trip to Scotland.  Here are some of the things we experienced. 

Scots Pine bark. 
Loch Garten Nature Reserve, Scotland. 

Scots Pine needles and immature female cones.
Loch Garten Nature Reserve, Scotland. 

Scots Pine mature female cone. 
Loch Garten Nature Reserve, Scotland. 

Scots Pine is found in the boreal forests of Eurasia and Scotland is the westernmost natural outpost of this tree.  People have transplanted it around the world for timber, pulp wood and as Christmas trees.  Plantation grown Scots Pine has a straight trunk and can reach over 100 feet.  Scots Pines growing in the wild on poor, acidic soil and exposed to the harsh weather of Northern Scotland are often gnarled and twisted.  They are a long-lived species with some surviving for more than 300 years.  As we walked through groves of these great trees we found ourselves speaking in hushed tones as if we were in a cathedral.  

Rowan (Sorbus acucuparia) tree.
Loch Garten Nature Reserve, Scotland. 

Rowan in flower.
Loch Garten Nature Reserve, Scotland. 

Another tree in the Ancient Caledonian Forest is Rowan (Sorbus aucuparia).  This is a small tree with compound leaves and when we saw them in June, they had white flowers that by fall would develop into red fruits.  

Common Juniper (Juniperus communis).
Loch Garten Nature Reserve, Scotland. 

Common Juniper (Juniperus communis) is a coniferous tree of the forest understory.  It has short, sharp needles and separate male and female trees.  Female trees bear fleshy cones called juniper berries.  The berries are added to gin, contributing to the drink’s distinctive flavor.  

Silver Birch (Betula pendula) leaves.
Loch Garten Nature Reserve, Scotland. 

Silver Birch bark.
Loch Garten Nature Reserve, Scotland. 

Betula pendula or Silver Birch has white papery bark and pendulous triangular leaves.  They were growing among the Scots Pines. 

Lichens.
Loch Garten Nature Reserve, Scotland. 

Lichens.
Loch Garten Nature Reserve, Scotland. 

Lichens are abundant on the ground, on rocks, tree trunks and branches in the forest.  These symbionts consist of a fungus and a photosynthetic alga living as a single organism.  Lichens are extremely sensitive to air pollution and their abundance in the forest was clear indication of good air quality.     

Bracken (Pteridium aquilinum).
Loch Garten Nature Reserve, Scotland. 

Bog Cotton (Eriophorum angustifolium) fruits.
Loch Garten Nature Reserve, Scotland. 

Smaller plants in the forest include Bracken (Pteridium aquilinum).  This fern has large leaves that turn golden-brown in the fall.  Bog Cotton or Cotton Grass (Eriophorum angustifolium) is a sedge found in northern regions of both the New World and Old.  It makes tufts of white fruits that resemble cotton bolls.  While this plant is not used for textiles, the fruits were once used to make bandages and paper.  

Common Chickweed (Stellaria media).
Bogach, Scotland. 

Common Chickweed’s (Stellaria media) white flowers were in the forest understory.  This is the same chickweed we have growing in our yard and came to us from Eurasia.  It was a treat to see Common Chickweed in its native habitat.  

Black Slug (Arion ater).
Bogach, Scotland. 

There were animals too, both large and small.  We found several Black Slugs (Arion ater) in the forest.  These impressively large gastropods can reach six inches in length and are shiny black.  Black Slugs are hermaphrodites with both male and female genitals.  They consume dead plant material, mushrooms, carrion and decomposing plant material.  Authorities claim Black Slugs are edible but taste horrible.  Echoing the adage that everything is edible, once.  

Common Chaffinch (Fringilla coelebs).
Bogach, Scotland. 

Common Wood Pigeon (Columba palumbus).
Loch Garten Nature Reserve, Scotland. 

Birds were abundant in the forest.  Some of the birds we found were Eurasian Chaffinches (Fringilla coelebs) and the plump Common Wood Pigeons (Columba palumbus). 

Spotted Flycatcher (Muscicapa striata). 
Loch Garten Nature Reserve, Scotland. 

Spotted Flycatcher on nest. 
Loch Garten Nature Reserve, Scotland. 

Willow Warbler (Psylloscopus trochilus). 
Loch Garten Nature Reserve, Scotland. 

Common Sandpiper (Actitis hypoleucos).
Loch Garten Nature Reserve, Scotland. 

A Spotted Flycatcher (Muscicapa striata) was tending its nest and Willow Warblers (Psylloscopus trochilus) sang from the trees. Common Sandpipers (Actitis hypoleucos) perched along the shore of the loch and probably had a nest nearby.   

Mistle Thrush (Turdus viscivorus). 
Loch Garten Nature Reserve, Scotland. 

We found a Mistle Thrush (Turdus viscivorus) feeding in a clearing.  This large thrush looks much like our American Robin (Turdus migratorius) in form but is spotted on the breast.  

Red Kite (Milvus milvus).
Arabella, Scotland. 

The most impressive bird we found was the Red Kite (Milvus milvus).  These large raptors feed mostly on carrion but will also take small animals.  They were mercilessly persecuted for hundreds of years and became extinct in Scotland in the 19^th century.  In the 20^th century Red Kites were protected by law and have been reintroduced over much of their former range.  One of the Red Kites we saw had a radio transmitter on its back to monitor its movements and activities.  

Red Deer (Cervus elephus).
Insh Marshes Nature Reserve, Scotland.

Mammals also inhabit the Ancient Caledonian Forest. Red Deer (Cervus elaphus) are native to much of Europe and Western Asia and have been transported around the world as game animals.  We found a young buck browsing in a meadow.  

River Otter (Lutra lutra) with fish.
Loch Garten Nature Reserve, Scotland. 
 

River Otter.
Loch Garten Nature Reserve, Scotland. 

We had the good fortune to see a Eurasian River Otter (Lutra lutra) swimming in a Loch.  This charismatic animal declined in much of Great Britain during the 20^th century due to pollution and habitat loss, but their numbers remained strong in Scotland.  Dave Cullen our guide to the Ancient Caledonian Forest, had been a ranger at this preserve and knew otters were present but he had never seen them.  He was quite excited when we spotted this one.  When a guide is impressed by a sighting you know it is significant.  

Steve and Diane Coggin in the
Ancient Caledonian Forest.
Loch Garten Nature Reserve, Scotland. 

Today the Ancient Caledonian Forest is a shadow of its former self.  It probably reached its greatest extend about 5000 years ago.  Then the climate began to warm and became wetter.  People felled the trees for timber, and created agricultural and grazing land which diminished the forest further.  By the mid-20^th century only about 1% of the forest remained.  Now a movement called rewilding is going on in Scotland.  It seeks to bring back the forest by replanting the native flora and reintroducing keystone animals.  This is an admirable effort to undo some of the damage we have done to the Ancient Caledonian Forest over the millennia.

Whence the flowers?

 

Zebra Swallowtail (Eurytides marcellus) on
West Indian Lantana (Lantana camara).
Rowan County, North Carolina.

High summer is upon us, and the flowering abundance of spring is behind.  But our yard still has some plants in flower.  They bring color to the yard and food for the small creatures that live among us.  Some of these plants are natives but many of the summer bloomers are introduced from somewhere else in the world.  As I was admiring the summer flowers I was inspired to explore the geographic origin of our plants.  

Common Zinnia (Zinnia elegans).
Rowan County, North Carolina. 

Common Zinnia (Zinnia elegans) comes in many colors and sizes.  It originated in dry tropical regions of Mexico and Central America but is now planted in gardens throughout the world.  A wide variety of insects sip the Zinnia's nectar while gathering pollen.   

Purslane (Portulaca sp.).
Rowan County, North Carolina. 

Purslane. 
Rowan County, North Carolina. 

Purslanes (Portulaca sp.) can be found in both the Old World and the New.  These drought and heat tolerant plants are succulents and the flowers open only on sunny days for a few hours after sunrise. 

Shasta Daisy (Leucanthemum x superbum).
Rowan County, North Carolina. 

Shasta Daisies (Leucanthemum x superbum) have an interesting history.  It is a hybrid produced by American plant breeder Luther Burbank in the late19^th century.  He crossed, in succession, four different species of daisies from Europe and Asia to make this tall, hardy and prolific plant. 

Purpletop Vervain (Verbena bonairensis).
Rowan County, North Carolina. 

Verbena bonairensis or Purpletop Vervain is a tall spindly plant that makes clusters of small purple flowers on the tips of the stems. It originated in South America and is now widely grown in gardens.  Purpletop Vervain is a favorite of pollinators including butterflies and bees. 

Common Milkweed (Asclepias syriaca).
Rowan County, North Carolina. 

Butterfly weed (Asclepias tuberosa).
Rowan County, North Carolina. 

Monarch Butterfly (Danaus plexippus) caterpillar 
on Common Milkweed.
Rowan County, North Carolina.

Two native species of milkweed flower throughout the summer in our yard.  The tall, purple flowered Common Milkweed (Asclepias syriaca) and  the short, orange flowered Butterflyweed (Asclepias tuberosa) attract pollinators and provide food for Monarch Butterfly (Danaus plexippus) caterpillars.  

Balsam (Impatiens balsamina).
Rowan County, North Carolina. 

Balsam (Impatiens balsamina) is an annual with thick, succulent stems. Flowers range in color from white to red.   Balsam makes large fruits that explosively scatter seeds when touched giving rise to another common name, Touch-me-not.  Balsam is favorite of hummingbirds in our yard. 

Scarlet Beebalm (Monarda didyma).
Rowan County, North Carolina. 

Scarlet Beebalm (Monarda didyma) is a member of the mint family (Lamiaceae) and is native to Eastern North America. It produces abundant red flowers.  As the name Beebalm suggests they are pollenated by bees but they are also attractive to hummingbirds.   

West Indian Lantana with yellow and orange flowers.
Rowan County, North Carolina. 

West Indian Lantana with yellow and purple flowers.
Rowan County, North Carolina. 

West Indian Lantana (Lantana camara) is related to Verbena bonairensis and it also originated in tropical America.  Its abundant flowers and drought tolerance have allowed it to spread around the globe as a garden plant.  Flowers are borne in clusters on the ends of branches. The newest flowers are at the center of the cluster and older flowers to the outside. We have two different colored Lantana flowers in our yard.  One type has flowers that open yellow and turn orange as they mature.  Another starts yellow and turns purple.  With these brilliant flowers West Indian Lantana is a favorite of wide variety of insects. 

St. John's Wort (Hypericum calycinum).
Rowan County, North Carolina. 

Hypericum calycinum or St John’s Wort is a small shrub.  Its natural range is Turkey and Southeastern Europe.  St. John’s Wort makes large, yellow, five-petaled flowers with many stamens.  This is another widely planted species and is found in gardens in temperate regions. 

Bottlebrush Buckeye (Aesculus parviflora).
Rowan County, North Carolina.

Bottlebrush Buckeye (Aesculus parviflora) is a small tree native to the Southeastern United States.  It naturally grows in rich woodlands but is widely planted as an ornamental.  Bottlebrush Buckeye flowers in summer and produces a spike of white flowers. 

American Beautyberry (Callicarpa americana).
Rowan County, North Carolina. 

American Beautyberry (Callicarpa americana) flowers in midsummer and its white flowers come in clusters born at the base of the opposite leaves.   In the fall American Beautyberry makes beautiful purple berries that are a favorite food of wildlife.  This handsome shrub is native to the Southeastern United States. 

As I work on this blog the outside temperature on the Piedmont of North Carolina is about 100 degrees.  All the plants, animals and people are stressed by this heat.  We have a number of plants native to this part of North America, but it is striking how many of the flowers are of tropical origin or from dry environments.  I expect plants that tolerate our hotter and dryer environment to be more and more common in our gardens as the climate changes.