Ramble Report March 8 2018

Today's Ramble was led by Dale Hoyt.

The photos in this post, except where noted, came from Don's Facebook album (here's the link).
(Note added after posting this page.
Don returned to the Dunson Garden in better (warmer) weather and got some spectacular photos of Trout Lillies and other spring flowering plants. View his album here.)

Today's post was written by Dale Hoyt.

26 Ramblers met today. Introduced were three new ramblers, Susie and John (who joined us last week), and AJC nature columnist Charles Seabrook.

Show & Tell: Sue brought in a Luna Moth cocoon that she recently found in Memorial Park. Luna caterpillars are polyphagic, which means that they eat the leaves of a variety of trees. I've reared them on Sweet Gum, but they have been recorded eating Hickory, Walnut, Maple, Ash and many others. Their preferences vary regionally.

Today's reading:

Avis read a Mary Oliver poem, Spring, from the collection titled Blue Iris: Poems and Essays.

Bob Ambrose recited another of his original creations, Reading on my Back Deck One Balmy Winter Day.

Today's route: We repeated last week's route to the Dunson Garden, then to the temporary pool in the power line ROW and back.

This morning was chilly, with temperatures in the low forties at the beginning of our ramble. Consequently some of the plants we saw last week refused to open their blossoms. This could be a way to protect their pollen supply when conditions threaten storms and insects are not active.

A question for my readers.

This is my 6th year writing this blog and I'm finding that it is becoming repetitious. Each ramble visits one of a small number of spots in the garden and we always come upon new and interesting things. But we also see a lot of the same stuff. Except for the new people, don't you get tired of stopping at the same Hophornbeam on the Purple trail and listening to the same spiel about Yellowbellied Sapsuckers and then reading the same words in this blog a few days later? Or is that repetition useful?

Don Hunter does a fantastic job of capturing images of what we see and he posts them in his Facebook album and, now, in the Nature Rambling Facebook group. This resource should be sufficient to document where we went and what we saw. 

I would like to abandon the chronological travelogue format that I've been doing the past five years and instead focus on interesting things that are related to what we see. These might be identification tips, or interesting life history quirks, or ecological perspectives related to what we see. This post is an example of what I'd like to do.

Please let me know what you think!

Yellow Trout Lily
The mottled leaves are the basis for the "trout" name.
The flower is closed because of the low temperature.

A colony of Yellow Trout Lillies is growing at the foot of a large tree in the Dunson Garden. Most of the plants in this group have a single leaf and do not flower. They simply bide their time, storing energy they accumulate during the few weeks they are able to bask unimpeded by the canopy of leaves overhead. When they have stored enough food in their underground corms they will produce two leaves and a single flower stalk. It takes 5-7 years to accumulate that amount of food. At any one time only a small fraction (1% or fewer) of the colony will be able to produce a flower. (A second species of Trout lilly, Dimpled Trout Lily is also found in the DNFG; it does not usually form such large colonies.)

Someone asked "Why are they called Trout lilies." Common names don't have to make sense and frequently they don't. In this case the name alludes to the mottling and shape of the leaf. It reminded someone of a trout. But that's not the only name by which these flowers have been (or are) known. Let me quote from Mary Durant's Who Named The Daisy? Who Named The Rose?, 1976, Dodd, Mead & Co., NY, pp. 199-201:

   Trout lily, however, is a fairly recent American nickname; so is fawn lily, given because the spots on the leaves can also be compared to the spotting on a fawn. This last originally referred to a California species, but is coming into use as a general name, as John Burroughs first suggested almost ninety years ago, though most wildflower guides have not picked up on it yet. Burroughs not only remarked on the fawn-spotted leaves but further wrote: "I have sometimes come upon a solitary specimen of this yellow lily growing beside a mossy stone where the sunshine fell full upon it. Its two leaves stand up like fawn's ears, and this feature, with its recurved petals, gives it an alert, wide-awake look."

   Two early nicknames still with us are adder's tongue and dog tooth violet, both choices due to that "reckless fashion" of christening New World plants with Old World names . . . There is nothing about these lilies to suggest an adder's tongue, but it obviously was the nickname for some European plant or other that seemed similar. Nor is there anything to suggest the teeth of a dog, and these flowers are lilies, not violets. A Eurasian variety of trout lily has dog-toothed roots (its early Latin name was dens canis), and the flower is violet, so dog-tooth violet became a catch-all English term for the entire family and was given to the American species when they were first discovered.

Red Maple staminate (male) flowers; 4-5 flowers have emerged from a single bud.
Stamens extend far out from the petals; petals are reduced in size and don't interfere with pollen dispersal by wind.
(photo by Dale Hoyt)

Staminate (male) catkins of Hophornbeam.
Each "bump" is an unopened flower and will release pollen to the wind when mature.

Wind pollination

With their display of showy petals the wildflowers that have been blooming in the last few weeks are attempting to attract a pollinator. In a few weeks more the trees will begin to leaf out, but many of them will flower first. Some, like Red Maples already have. In last week's Oconee Rivers Audubon Society meeting the speaker mentioned that most of the native trees in the Eastern Deciduous Forest of North America are wind pollinated. At today's ramble, Tim asked me if I thought that was really true, so I've started to research this topic. It turns out that there are a lot of interesting facets to the subject. Here are the results so far.

Wind-pollinated trees in our area.

The kinds of native trees in our area that are wind pollinated: ashs, elms, beech, oaks, hazel, alder, birch, walnut, hickory, chestnut, hackberry, mulberry, sycamore, sweetgum, hornbeam, hophornbeam and, of course, red cedar and all the different pines. The pines and red cedar and all are gymnosperms (non-flowering plants) but all the others are flowering plants (angiosperms).

Do wind-pollinated flowering plants have flowers?

None of the trees in that list have what you would normally think of as flowers, so where are they? Their flowers are just not very showy. Consider the oaks. Every spring, slightly before or just as their leaves begin to appear, the oaks produce "tassels," or catkins. These are long, greenish-brown fuzzy structures that hang from the twigs for about a week and then fall into the gutters on your house. Each tassel bears dozens of small, petal-less, pollen producing male flowers. And they produce prodigious amounts of pollen that gets carried by the wind. The lucky pollen grain comes in contact with the inconspicuous female flowers on other oak trees to set off the chain of events that leads to the production of an acorn. The oak is representative of many features of wind pollinated plants:

1.     Flowers emerge before the leaves.

2.     Petals are greatly reduced or absent.

3.     Production of copious amounts of pollen.

4.     Pollen grains are small, dry and easily dispersed in the wind.

5.     Flowers are usually unisexual. Either male (staminate, pollen producing) or female(pistillate, seed producing). The male and female flowers may occur on separate trees or both appear on the same tree, but in separate flowers.

What is a flower?

You may need to readjust your thinking about what a flower is. You probably learned that a flower has the following parts: sepals, petals, stamens and pistil. That's what a typical flower has. But the essence of a flower is the reproductive structures: the stamens and the pistil(s). A flower is a thing that can produce pollen or seeds or both. Sometimes it has pretty petals but it doesn't have to. In a wind-pollinated flower the petals just get in the way; getting rid of them exposes the pistil(s) to the pollen bearing breezes.

Wind pollination, latitude and elevation.

The proportion of wind pollinated trees increases with latitude and elevation. At the extreme, the boreal forest of Canada are composed of almost 100% conifers. This increase is also seen with changes in elevation. If you were to walk from the lowest elevations to the highest in the Great Smoky Mountains NP you would see the proportion of wind pollinated species increase from 17% to 71%. But that is just counting species. If you count the stems, the actual number of trees, not just tree species, the proportions range from 19 to 90%. (This excludes the uppermost elevations that are !00% spruce and fir.)

Conversely, as you travel to the tropics you find an increase in the number of trees pollinated by animal agents (insects, birds, bats and other mammals).

But why?

The really interesting question is why this pattern should be the case. Perhaps you can think of some reasons. (To be continued in future posts.)

Blueberries, like this Highbush Blueberry, must be pollinated by insects.

Blueberries and buzz pollination.

The Highbush Blueberries have been blooming for a least a week. In order to produce fruit the flowers need to be pollinated. In theory you just need one pollen grain per flower to produce a berry, but will be pretty small. It turns out that multiple grains of pollen produce berries with three or more seeds and the more seeds the larger the berry (within reason). So the efficiency of the pollinator is important. Blueberries are a native crop and there are many native bees that are effective pollinators. North Carolina State Extension service has a very nice page devoted to blueberry pollinators. Of all the native pollinators and the non-native honeybee the best is the Bumblebee and many blueberry growers supplement their fields with bumblebees. Bumblebees use a technique called sonication or buzz pollination to extract pollen from the plants they visit. The bee grasps the flower and vibrates its flight muscles without moving its wings. This produces a high pitched buzz and, more importantly, shakes the pollen out of the stamens. The Leonard lab at the University of Nevada, Reno, has excellent videos of bumblebee sonication.

Some plants are exclusively pollinated by sonicating bumblebees: members of the Nightshade family, Solanaceae; e.g., potatoes, tomatoes, peppers and eggplants. Members of this family have a specialized anther structure. Instead of splitting open along its length and revealing all its pollen, the solanaceous anther remains closed, except for a tiny opening at its tip. In addition, the pollen grains inside are dry and not sticky as the typical pollen grain of an insect pollinated plant is. When a solanaceous flower is sonicated a puff of pollen is shaken from the anther and is attracted to the furry body of the bumblebee by its electrical charge.

This Field Pansy has curled petals because it's so chilly this morning.

Field Pansies are delicate flowers that hide in the grasses of unkempt areas. As their name implies, they resemble tiny pansies. Linda showed us that they also harbor another surprise: scraping their root with your fingernail releases the scent of wintergreen.

The finger-like projections at the base of the leaf petiole are stipules.

She also showed us their unusual stipules, a pair of leaf like structures that arise at the base of the petiole, the point where the leaf is attached to the stem.

Field Pansies are surprising in another way: they have two ways of dispersing their seeds. Their seed capsule is made of three parts, each bearing a row of seeds.

A Field Pansy seed capsule opened and ready to squeeze out its seeds.
(photo by Dale Hoyt)

When they mature the capsule splits between each of the parts and opens out into a Y shape, with the seeds still attached to the capsule walls. Then the capsule walls begin to dry, folding and shrinking around the seeds. This squeezes the seeds tighter and tighter until they pop out of the capsular embrace. If unobstructed they shoot a distance of several feet from their parent. The force that propels them is like a child shooting watermelon seeds by squeezing them between thumb and finger.

Field Pansy seeds; the white structures are elaiosomes.
(photo by Dale Hoyt)

Now that they have been dispersed some distance from their parent plant a second opportunity to travel further is revealed. Each seed has an elaiosome, a fat and protein rich projection that is attractive to ants. When ants discover the seed they carry it back to their nest, remove the elaiosome and feed it to their larvae. The seed is carried to the ants refuse area and discarded beside the bodies of dead ants and other waste.

This dual method of dispersal is also found in the other kinds of violets, like the Common Blue Violet. You can bring one inside and set it on the dining room table. In a few weeks you'll be surprised!

SUMMARY OF OBSERVED SPECIES:

Allegheny Spurge	Pachysandra procumbens
Rue Anemone	Thalictrum thalictroides (= Anemonella thalictroides)
Chattahoochee Trillium	Trillium decipiens
American Trout Lily	Erythronium americanum
Bloodroot	Sanguinaria canadensis
Cutleaf Toothwort	Cardamine concatenata (=Dentaria laciniata)
False Rue Anenome	Enemion biternatum
Perfoliate Bellwort	Uvularia perfoliata
Golden Ragwort	Packera aurea
Trailing Trillium	Trillium decumbens
Dwart Trillium	Trillium pusillum
Virginia Bluebells	Mertensia virginica
Dimpled Trout Lily	Erythronium umbilicatum
Lanceleaf Trillium	Trillium lancifolium
Celandine (Wood) Poppy	Stylophorum diphyllum
Halberd-Leaved Violet	Viola hastata
Edna's Trillium	Trillium persistens
Sweet Betsy Trillium	Trillium cuneatum
Highbush Blueberry	Vaccinium corymbosum
Field Pansy	Viola bicolor
Black Cherry	Prunus serotina
Eastern Redbud	Cercis canadensis