Plants That Bite Back – Part 2

It commonly chances that I make my most interesting botanical discoveries when I am in a thrilled and expectant mood…some rare plant which for some reason has occupied a strangely prominent place in my thoughts for some time will present itself. My expectation ripens to discovery. I am prepared for strange things.

~Henry David Thoreau, 1856

The strange and miraculous Venus flytrap was the subject of the last post. But, North Carolina is home to a variety of other carnivorous plants, and we saw many of them on our recent trips to the Green Swamp and Holly Shelter. Here is a quick summary of some of these amazing insect-eating flora…

Butterwort flower and leaves

Butterwort flower and leaves (click photos to enlarge)

Butterworts – Pinguicula sp.- Latin, pinguis, means fat. Common name refers to glistening leaves. Three species of this plant equivalent of flypaper are found in NC.

Purple butterwort  flower and base

Blue butterwort, Pinguicula caerulea

Pinguicula lutea flower

Yellow butterwort, P. lutea

_-5

Small butterwort, P. pumila

_-9

Basal rosette of butterwort leaves act like flypaper

The leaves of butterwort use two specialized glands, scattered across the leaf surface, for prey capture and digestion:

_-8

Close-up of butterwort leaves

1) a peduncular gland, consisting of a few secretory cells on top of a single stalk that produce a mucilaginous secretion that traps insects; 2) sessile glands, which lie flat on the leaf surface and release enzymes that digest soft parts of the insect body. These fluids are then absorbed back into the leaf surface through holes. Butterworts produce a strong bactericide which prevents insects from rotting while they lay exposed on the leaves and are being digested. This property has long been known by northern Europeans, who applied butterwort leaves to the sores of cattle to promote healing.

Bladderwort mass

An aquatic species of bladderwort

Bladderworts – Utricularia sp. – Latin, utriculus, meaning wine flask, leather bottle, bladder, small womb, or bagpipe; refers to the shape of the trapping mechanism.

Bladderwort traps

Bladderwort traps are small pouches attached to stolons

Bladderworts are the largest genus of carnivorous plants with over 200 species worldwide. About 16 species are found in NC with most found in the Coastal Plain. Most are aquatic or occur in wet soils. They lack roots, but they do have underground or underwater stolons (creeping plant stems) that behave as roots.

_-6

The most common bladderwort we saw was the tiny terrestrial species, U. subulata, that grows in wet sand

Bladders are scattered along the length of the plant under water (or wet soil) suspended from small stalks. Each is concave, under pressure, and sealed by a trapdoor kept watertight by a mucilaginous sealant. One touch of the tiny trapdoor trigger hairs, and the door swings open sucking prey and surrounding water into the low-pressure trap. Their traps suck in prey in less than one one-hundredth of a second, making this one of the speediest movements in the plant world. Once the prey is inside, a swirl of water pushes the door back again and the prey is trapped. Glands on the the inside of the bladder secrete enzymes that dissolve soft-bodied prey within hours. Other cells transport water back out of the trap, and it is reset.

_

Sundews in a roadside ditch

Sundews – Drosera sp. – Greek for dewy. One of the most abundant groups of carnivorous plants with over 160 species worldwide. There are five species in NC.

_-4

Close-up of a leaf of D. intermedia

Leaves lure, capture, and digest insects using stalked mucilaginous glands covering their leaf surfaces. These hairs trap insects in the sticky “goo”, and then proceed to digest them.

sundew with prey

Leaves often curl to help pool the released enzymes and nutrients

Sundews move their tentacles toward their prey, causing them to get even more stuck.

sundew flower stalk with insects 1

Even the flower stalks and buds of D. brevifolia seem to trap small flying insects

Enzymes dissolve the prey and released nutrients are then absorbed through the leaf surface.

Holly Shelter oitcher plants

Yellow pitcher plants at Holly Shelter Game Lands

Pitcher plants – Sarracenia sp. – After Michel Sarrazin (1659–1735), the first naturalist to send pitcher plants to Europe for study. Pitcher plants are passive pitfall traps (they don’t move). Pitchers are modified leaves and many species have lids or hoods which keep out rainwater.

unopened S flava leaf

Yellow pitcher plant leaf before the trap tube opens

Prey are lured by nectar and colors/patterns on the pitcher that mimic a flower. At least one species, S. flava, has a toxic alkaloid in the nectar that may intoxicate prey.

cut pitcher plant

Dissected pitcher showing downward pointing hairs and prey

Prey fall into the trap due to the slippery inner wall of the upper section. Narrowing diameter of the tube and downward pointing hairs in lower portions further inhibit escape. Digestive enzymes are secreted and nutrients are absorbed by the plant tissues.

Sarracenia purpure

Purple pitcher plants lack a lid and collects rainwater

Prey are believed to drown in the open pitcher of purple pitcher plants, S. purpurea. Microorganisms living inside the pitchers contribute to decomposition and nutrient uptake by the plant. If you look inside one of these pitchers, you may see things swimming in what you would think would be a deadly soup. We pulled a turkey baster full of liquid out of one pitcher and found both prey remains and living organisms that use it as a home.

Picture

The material siphoned out of a purple pitcher plant pitcher…yellow lines indicate a live mosquito larva and pupa; the blue line is a live midge larva

The larvae of a small, non-biting mosquito (Wyeomyia smithii) and a midge (Metriocnemus knabi) live in the liquid in the pitcher, somehow withstanding the digestive enzymes that kill other insects.

This has been a quick glimpse into the lives of these strange and wonderful plants. I have so much more to learn about these amazing plants and their specialized adaptations for surviving in nutrient poor soils in these intriguing habitats.

Green Shelters

The distinctive roar of the longleaf was the sound the evening breeze made, and the odor of pine resin was the smell of the countryside…It was so much a part of their lives, so wound up with everything it meant to be southern, that it was as impossible to discern its influence as it was to imagine a world without it. Only when it was reduced, almost entirely, to a sea of stumps could we begin to get our arms around it.

~~Bill Finch in Longleaf, Far as the Eye Can See

These past few weeks have flown by with so much happening both at work and home. Highlights have included a couple of trips to a region of North Carolina that is quickly becoming a favorite, and is home to extensive longleaf pine savannas and their associated diversity of plants. The place is southeastern North Carolina, and the destinations are the Green Swamp Preserve and Holly Shelter Game Lands. One trip was with some of our trained volunteers from the NC Botanical Garden. The other was an educator trek highlighting the carnivorous plants of the region. Both were in collaboration with the NC Museum of Natural Sciences. Compared to our home here in the Piedmont, this land of longleaf really is a different world in the way it looks, feels, and sounds.Here are a few highlights from those trips (spoiler alert…more to come in future posts)…

Longleaf pine savanna

Longleaf pine and wiregrass along a road in Holly Shelter Game Lands (click photos to enlarge)

The classic longleaf savanna has a dense understory of wiregrass and a host of other herbaceous species under a canopy of tall longleaf pines. Variations of this conifer-dominated community once covered 90 million acres along the Atlantic and Gulf Coasts. Logging, the naval stores industry, land conversion, and fire suppression have reduced this once dominant plant community by 97%. Land managers are working to restore this treasure by using a tool that helped shape this diverse landscape – fire.

Grass stage of longleaf pine

Grass stage of longleaf pine following a prescribed burn

Scientists estimate natural lightning-caused fires once occurred on average every 3 to 7 years in much of the Coastal Plain. Years of fire suppression shifted the balance in plant communities to favor more deciduous species like turkey oaks at the expense of longleaf pines and the associated savanna species. Regular burns are helping turn this around, allowing the fire-adapted species to once again thrive. At both sites, we saw evidence of the adaptability of the many growth stages of longleaf to the effects of fire (see Melissa’s post from last year on longleaf). Plenty of singed needles, but the majority of growth tips survived, helping create a patchwork of green in the charred landscape.

Bottlebrush stage of longleaf after fire

Bottlebrsush stage after a fire

Looking down on growing tip of bottlebrush stage of longleaf aft

Growth tip of a longleaf pine in the bottlebrush stage

Bring the plants back and you start to bring back the animals as well.

Red-cockaded woodpecker nest cavity

Red-cockaded woodpecker nest cavity surrounded by sap flow

The federally endangered red-cockaded woodpecker depends on mature longleaf pine forests for its nesting cavities. They are the only woodpecker that regularly excavates cavities in living trees. As such, they are considered a ‘keystone’ species, because use of their cavities (either for roosting or nesting) by at least 27 other species of vertebrates contributes to the species richness of the pine forest. We saw numerous cavity trees scattered about the savannas. Most are marked in two ways – one human, one avian. Researchers monitoring the birds’ population regularly mark nest trees with two bands of white paint around the trunk of the tree. The birds drill numerous holes above and below the nest entrance, creating a sap flow that dries a whitish color and is visible at considerable distances. The sap is believed to help reduce the threat to eggs and nestlings from predators such as rat snakes.

_-5

Dwarf azalea in pine savanna

Flower buds of dwarf azalea

Dwarf azalea flower buds

Dwarf azalea

Dwarf azalea blossom

At our last stop in Holly Shelter, we enjoyed the beauty and fragrance of dwarf azaleas, Rhododendron atlanticum. This low-growing shrub makes an eye-popping display in the sea of wiregrass. A closer look revealed some other striking flowers under the pines.

Iris verna

Dwarf iris, Iris verna, in the Green Swamp

grass pink orchid flower

Grass pink orchid

The pine savannas are known for their unusual plants, including a host of native orchids. Early in the season, the grass pink orchids, Calopogon sp., dominate. The genus name is Greek for “beautiful beard”, referring to the cluster of yellowish hairs on the upper lip of the flower. This flower produces no nectar, but the bushy hairs resemble the pollen-bearing anthers of other flowers, thus fooling insects to land for a snack.

grass pink orchid flower showing hinged upper lip

What happens when a bee lands on the fake anthers of a grass pink orchid flower

The upper lip of the orchid is hinged at the base. When an insect lands on it, the lip drops, flopping the insect onto the reproductive parts of the flower (called a column) hopefully leading to pollination. In the photo above, the twig pushing down on the lip shows what happens when an insect, such as a bumblebee, lands on the yellow hairs – it is dropped down onto the column.

Fly on meadow beauty seed vessels

Fly resting on old seed pod of meadow beauty

We also saw a lot of other insects in the savanna including many Palamedes swallowtail butterflies. And where there are insects, there will be spiders, waiting…

Crab spider on flower

Crab spider awaiting its next meal

wolf spider with babies

Wolf spider with babies and egg sac

This mother wolf spider is carrying her egg sac on the tip of her abdomen while the spiderlings hatch and crawl onto her back. They will cling to her for a few days until their first molt.

wolf spider with babies close up

Hitching a ride with mom

Our savanna time was well spent and we all came away with a new appreciation of the magic of this habitat. The gentle roar of the wind in the pines is definitely a soothing sound.

Longleaf pines and sunlight

Longleaf pine canopy in the Green Swamp Preserve

And, if you take the time to stoop down and look closely, there are many marvels to see…

looking at flytraps

What are they looking at?

Stay tuned…

 

 

Where Insects Fear to Tread

There is no exquisite beauty …without some strangeness.

~Edgar Allan Poe

Part two of our quest for carnivorous plants took us first to the Green Swamp, a well-known NC Nature Conservancy preserve site in Brunswick and Columbus counties. It was getting late in the day, so we went straight to the main access point, a small parking area next to a borrow pit along Hwy 211. We hiked in along the trail, through a short stretch of dense pocosin vegetation, and out into the open longleaf pine savanna.

Longleaf pine savanna, Green Swamp

Longleaf pine savanna in the Green Swamp (click photos to enlarge)

What you find here often greatly depends on the fire regimen – the year after a burn can produce spectacular wildflowers and make it much easier to see any in bloom. From the looks of it, I am guessing it may have been over a year since this particular tract was burned, but we could see some scattered spots of color poking above the clumps of wiregrass, especially along the pocosin edge.

Gras pink orchid

Grass pink orchid, Calopogon sp.

In addition to insect-eating plants, these pine savannas are well-known for their gorgeous orchids. Calopogon comes from the Greek words meaning beautiful beard, and refers to the bushy, yellow protuberances on the lip of this delicate orchid. These are designed to attract pollinators, thinking there might be a pollen or nectar reward, but it is a deception. The lip of the flower is hinged at the base, and when an insect lands, the lip drops and traps the insect among the flower parts, forcing it to wriggle its way out, and, in the process, hopefully pollinating the flower.

Butterwort

Yellow butterwort, Pinguicula lutea

Scattered along the edges of the savanna are small, bright yellow flowers of a carnivorous species, the yellow butterwort.

Butterwort leaves

Basal rosette of a butterwort

The business end of a butterwort lies at the base, where a tight cluster of sticky leaves serves to trap small insects by means of tiny stalked glands covered in mucilage. Other glands release digestive enzymes to help dissolve the soft tissues of the prey, with the nutrient-rich juices being absorbed by the leaf to supplement its nitrogen supply in this nutrient-poor environment.

Sundew

Pink sundew, Drosera capillaris

A similar, but more active strategy, is employed by another insect-eater, the sundews. Tiny rosettes of red leaves covered in what look like dew-covered hairs dot the moist soil in the savanna, especially any place that is muddy along a trail or ditch.

Sundew with prey

Close-up of a sundew leaf with a trapped insect

When a potential prey touch the stalked glands, it gets stuck in the “goo”. Adjacent tentacles move toward the prey, further entrapping it. Digestive enzymes are released and the rest is history.

We finally had to head back to camp, but a good day of carnivorous plant exploration with sundews, two species of pitcher plants, butterworts, two species of bladderworts, and some Venus flytraps. The next day would prove to be even better.

Longleaf pine savanna Holly Shelter

Longleaf pine savanna in Holly Shelter

I had heard about Holly Shelter Game Lands for many years, but never managed to visit until now. It consists of over 63,000 acres of mixed forest, pocosin, and other wetlands in Pender County. Since it is turkey season, we were advised to visit on Sunday when there is no hunting. We drove along miles of dirt roads to several spots recommended by a friend for their plant diversity.

Carolina laurel

Carolina wicky, Kalmia carolina

Horse sugar

Horsesugar, Symplocos tinctoria

A few small shrubs adding splashes of color in the longleaf forests, including a Coastal Plain relative of mountain laurel, Carolina wicky (also known as Southern sheepkill). Small starbursts adorn another savanna shrub, horsesugar (aka sweetleaf).

Holly Shelter oitcher plants

Small pond at Holly Shelter surrounded by yellow pitcher plants, Sarracenia flava

Our first stop was amazing – hundreds of yellow pitcher plant flowers came into view as we approached a small pond. There was also the bright green of the emerging new leaves, so it was a perfect time to view this species.

Pitcher plant leaf before opening

An unopened pitcher leaf

It is easy to forget that in all of these carnivorous plants, it is the highly adapted leaves that are the trapping mechanism. In the case of the yellow pitcher plant, the leaf blade usually elongates a foot or more before the top splits open to form the deadly pitfall trap.

Pitcher plant opening

A leaf just beginning to split to form the pitcher

This pitcher has a hood (or lid) and usually has red veins that serve as nectar guides for potential prey, luring them deeper into the trap.

Fly going into pitvher plant

An open pitcher with an unwise fly

The trap is a simple one – lure your victim with nectar, a sweet reward concentrated along the rolled lip and down into the upper edges of the trap. Once inside, the walls of the pitcher change texture and become very slick, causing the insect to fall into the tube. Below the slippery zone, the walls have rows of down-ward pointing hairs that inhibit an upward escape. As the insect gets farther down into the trap, the tube narrows, making it more difficult for flying insects to use their wings to escape. Digestive enzymes at the base of the trap all but ensure the fate of the hapless insect.

Pitcher plant prey (2 pitchers)

Contents of two pitcher plants back at the NC Botanical Garden

A popular activity at work is for students to dissect old pitchers (last year’s leaves) and examine what the plant had for dinner. The enzymes only dissolve the soft tissues to release the needed nutrients, so the hard parts of prey remain – an assortment of wings, legs, and exoskeleton pieces. Coworkers gathered the insect parts from two pitcher plants in the Garden’s collection for the photo above: several moths (left side of photo); a cluster of flies (upper right); a wasp (top); some small beetles (lower right); and an assortment of unidentifiable wings, legs, and parts. A large amount of fine dust-like material from the trap is not shown in this picture. I need to collect a few dried pitchers from native habitats and see what the locals have been eating for comparison, but I have a feeling the menu could be similar based on that fly photo above. It was about to make a culinary misstep.

Purple pitcher plant

Purple pitcher plant, Sarracenia purpurea

Purple pitcher plants lack a lid and their pitchers usually contain rainwater. Prey fall into the pitcher and drown. Ironically, there is a species of mosquito, Wyeomyia smithii, whose larvae live in these pitcher plants and feed on the microscopic community that exists in the water.

Hybrid pitcher plant

Possible hybrid pitcher plant

We did see a few pitcher plant clumps that looked like hybrids between the purple pitcher plants and the yellow. The pitchers look like the S. purpurea, but are much more elongate, like an S. flava. The flowers also seem to be a combination of the colors of the two species – both maroon and yellow tints.

Sundew intermedia

Spoonleaf sundew, Drosera intermedia

Along the path were large numbers of the pink sundews we had seen in the Green Swamp, but the edge of the pond had another species. The spoonleaf sundew is more upright in growth form and seems to do well extending out into the water’s edge.

Sundew close up

A tiny insect trapped in the sticky goo of the sundew

I leaned down for a closer look and could see more victims that had fallen for the glistening droplets that adorn these deadly tentacles.

Purple butterwort  flower and base

Blue butterwort, Pinguicula caerulea

The Holly Shelter sites held two more species of butterwort – the blue and the correctly named small butterwort. The latter (which I failed to get a good photo of it turns out) has a pale, almost white flower, with a short flower stalk and a tiny rosette of leaves.

Purple butterwort group

Blue butterworts were very common

The larger, blue butterworts, were quite common and often occurred in patches of twenty or more individuals, scattered about the various sunny locations we visited.

Venus flytrap cluster

Venus flytraps, Dionaea muscipula, and a small purple pitcher plant

The Venus flytraps were amazing, as always, and abundant. Melissa mentioned all of these carnivorous plants in a recent post about one of her museum trips, so I won’t go into all the details of this, “one of the most wonderful plants in the world”, but I will share a few interesting tidbits.

Slide1

Close-up of a flytrap leaf, showing the trigger hairs

The trap is a modified leaf and has 2 to 3 trigger hairs on each lobe of the trap. Two triggers must be touched in succession within about 20 seconds for the trap to “spring” (or one trigger twice). Closing in less than a second, the Venus flytrap is one of a group of very few plants capable of rapid movement (other local rapid movement plants include Eastern sensitive briar, Mimosa macrophylla, and bladderworts, Utricularia sp.). The fleshy “teeth” along the edge of the trap mesh together to form a closed cage around any prey (usually crawling insects and spiders). The whole trap squeezes together more tightly when the prey struggles. Enzymes are then secreted by minute glands on the inner surface of the lobes and the victim is digested over the next few days. Afterward, the trap reopens, awaiting its next target (each trap can only spring a few times before that leaf dies).

Venus flytrap

Emerging flytrap leaves

The name, Venus flytrap, refers to Venus, the Roman goddess of love. The genus, Dionaea, refers to Aphrodite, the Greek goddess of love and the daughter of Dione. The species name, muscipula, is Latin for mousetrap. It really is remarkable that the only place this amazing plant is naturally found is in about a 70-mile radius of Wilmington, NC.  This trip proved to be one of strange beauties and incredible adaptations, and is definitely one we will do again.