Today's report was jointly written by Don Hunter and
Linda Chafin with additions by Dale Hoyt. Don's album of photos from today's ramble can be found here.
33 Ramblers today.
Today's readings:
Bob Ambrose recited one of his new creations: Reverie - Afternoon in the
Botanical Garden and Marguerite read Howard Nemerov's Trees.
Today's route: We began with an observation
of the Ginkgo trees at the Shade Garden arbor then walked down the Shade Garden
walkway to the Dunson Native Flora Garden. We walked through the Dunson Garden
to the head of the wetlands display and returned the same way back to the Shade
Garden arbor, and, for many, on to the Visitor Center to the Cafe Botanica for
socializing over food and drink.
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| Gingko short shoots and pollen cones |
Ginkgo
trees at the Shade Garden Arbor.
Ginkgo trees have a geological presence stretching back 270 million years. They are usually regarded as Gymnosperms very distantly related to pine trees or cycads and their relatives. Unlike angiosperms, their seeds are not enclosed by an ovary wall. Each tree is either male or female; the male plants produce cones that look something like a cross between a miniature pine cone and an oak catkin. Female plants are undesirable because their "fruit" smells horribly when stepped on. (The "fruit" is not a true fruit; it is a seed surrounded by a soft, fleshy tissue and a hard tissue.) Occasionally an otherwise male plant develops a branch that produces fruit, but this is very rare.
The pollen produced by the male cones is potentially
allergenic, but Gingkos are seldom planted in sufficient numbers to be a
significant source of hay fever.
The long branches bear numerous short shoots along their
length. Each
short shoot starts life as a lateral bud that fails to elongate. Each year a
new bud forms at the end of the shoot, so it continues to elongate over time.
Since the growth is minimal the shoot is composed of has a series of little
ridges along its length, each ridge indicating a year’s miniscule growth. The
“long shoots” continue to grow and lengthen a normal amount. Some of our native
trees, such as birches and hollies, also produce short shoots. These stubby
structures typically bear a cluster of leaves and flowers at their tips. One
theory about the adaptive value of short shoots is that the flowers and fruits
are held extra close to the source of their energy–the leaf cluster. Also short
shoots allow for additional spacing of leaves within the tree’s crown, perhaps
exposing more leaves to the sun’s rays. Interestingly, short shoots may change
into long shoots after a few years.
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| Red maples with different color seeds |
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| Red maple developing winged seeds (samaras). Note that the red color is fading from the wings. |
Red
Maples at the lower parking lot.
At the end of the central island in the lower parking lot are a group of
Red Maple trees. One tree displays red flower parts at the ends of its
branches, another, much taller, tree bears light tan-colored parts on its
branch ends and a third tree is devoid of any ornamentation. Our initial
thought was that we were seeing something like genetic variation in the
coloration. Most Red Maples produce red flowers but a few lack the intense red
and have flowers that are light orange or yellow in color. But after watching
the red maples in my neighborhood I have a different explanation. The trees are
genetically variable, but in development, not flower color. Not all the maples
flower at the same time, but when they do their floral parts are a deep
crimson. As the seeds develop the ovary enlarges and transforms into the
familiar "helicopter seed" (the actual seed is a swelling at one end
of the wing). This increase in size is accompanied by a decrease in redness,
almost as if the red pigment was being diluted. Finally, the mature fruit becomes
tan in color and is released from the tree and flutters to the ground.
My conclusion is that the tree with tan colored branch tips began to
flower earlier than the tree with red branch tips. We are looking at genetic
variation in flowering time, not color. We can tell is this idea is correct by
carefully observing these same trees next year.
Shade Garden
 | |
| Buckeye leaves emerging from bud |
 |
| Buckeye leaves expanding |
Bottlebrush
Buckeye terminal leaf buds are opening now. This species blooms much later
in the year and spreads clonally, as seen by the many stems nearby.
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| Haxelnut male catkins |
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| Hazelnut female flowers The red structures are the stigmas that receive pollen. |
American hazelnuts (filbert) are blooming now, with the
conspicuous tan catkins (that hold male flowers) hanging from the slender limbs
and twigs. We also saw the not-so-obvious female flowers, with their tiny,
minuscule explosions of fine, deep pink to red thread-like stigmas. The
dangling, flexible catkins indicate that hazelnut, like other catkin-bearing
plants (e.g. oaks, birches), are wind-pollinated. Though no one in the group
has ever eaten them, American hazelnuts are said to be quite tasty.
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| Aucuba flowers |
Japanese Aucuba
On our way back to the arbor several Ramblers stopped
with Linda to look at a large flowering shrub, the Japanese Aucuba. The four-petaled flower has a startling
resemblance to the flower of the purple bedstraw plant. These two plants are
not in the same families, but botanists consider the two families closely
related (bedstraw is in the Rubiaceae family and Aucuba in the Garryaceae
family.)
Dunson Native
Flora Garden
 | |
| Chattahoochee trillium |
Not long after entering the Dunson Garden, we began to
notice many of the long-stalked Chattahoochee
trilliums, most with tight, upright buds but some with fully open flowers.
Linda recounted the life history of trilliums. The seeds take 1 to 2 years to germinate and then produce a single leaf. In successive years,
they develop a healthy rhizome and produce two, then three leaves, which increases the amount of
photosynthesis the plant can conduct. The plants finally flower in year seven.
Flowering and fruiting are energy intensive processes and it takes a robust,
healthy rhizome with lots of stored starches to support reproduction. This
process may be expedited in more southern locations like south Georgia or
Florida, where plants may flower in year five. (Trout lilies have the same
basic process of rhizome development, single-leaf years, and delayed
flowering.) We saw, at one little
trillium patch, examples of one-, two-, and three-leaved plants growing
together. It is suspected that trilliums are able to live for at least 100
years.
 | |
| Sweet Betsy trillium |
Although most of the trilliums in the Dunson Garden are Chattahoochee trillium, there are
several other species found at various locations, including the Sweet Betsy trillium. It has an
upright, maroon or bronze-colored flower, with nearly closed petals. Like the
Chattahoochee trillium, its leaves are mottled, almost camouflage-like, but
lack the distinctive white to silvery stripe seen on along the mid-vein of Chattahoochee
trillium leaves.
We saw a small patch of Trailing trillium, growing flat to the
ground, and hiding their short (usually 1-2 inch) stems. The stem has a
pronounced S-shape, which results in the leaves and flowers being held at
ground level.
Trilliums can be divided into two groups: those with a
flower stalk and those without (sessile). Chattahoochee trillium, Sweet Betsy
trillium, and trailing trillium have flowers without stalks–their flowers sit
directly on top of the leaves. Others such as the Georgia Dwarf Trillium and
Catesby’s Trillium, have stalks that hold the flowers well above the leaves or
sometimes curve downward, creating a “nodding” flower. Sessile trilliums have
mottled, variegated leaves and yellow, maroon, or bronze-colored flowers.
Stalked trilliums have solid green, unmottled leaves and flowers that come in
various shades of white, pink, and maroon.
 | |
| Georgia dwarf trillium |
One of the highlights of the morning was the discovery that
the Dwarf trillium are blooming.
There is only one small location in the garden where this trillium can be seen
and there are generally only a few plants to be seen. The scientific name for
this plant will soon be officially changed to Trillium georgianum recognizing that it is a species separate from Trillium pusillum and acknowledging that
it is endemic to the state of Georgia. The common name has also been changed to
reflect its location; it is now Georgia Dwarf Trillium. The plants in the
Dunson Garden were rescued from the original discovery location, which is
threatened with development, in northwest Georgia near Dalton.
Painted buckeye buds have opened and the leaves are
just emerging.
 | |
| Spring beauty with closed flower bud |
Eastern spring beauties have begun to bloom. We have been
seeing the grassy foliage for several weeks but this week we now have flowers
showing up. We saw several plants with tightly closed flowers this morning. They
were just beginning to open and will be fully open later in the day when they
receive more sun and warmth.
All the spring ephemeral plants have a short period of time
in which they must attract pollinators and develop and disperse their seeds.
Spring beauty is visited by several fly and bee species and one of these, the
Spring beauty bee (Andrena eriginae),
is a Spring beauty specialist. It is a solitary bee that depends almost
entirely on gathering Spring beauty pollen to feed its larvae. In a single
visit the Spring beauty bee can remove ~65% of the pollen from a flower. From
the point of view of the plant this pollen is lost or stolen. The bee delivers
only about 2% of the pollen it has collected to flowers that it subsequently
visits. It would seem that the plant is a victim. But the bees stinginess is
compensated by the frequency of its visits. At the time of year Spring beauty
blooms the bee is the most abundant pollinator and responsible for most of the
seed set by the plant. The bee, by exclusively relying on a single pollen
source, stakes the life of its offspring on the success of its food plant. For
if Spring beauty plants are eliminated by habitat disturbance, grazing by deer
or competition from invasive species, then the Spring beauty bees will become
extinct in that local area.
 | |
| Early meadow rue |
Early meadow-rue has just emerged and a few flowers are
visible on the low mounds of vegetation. As the season progresses the flowering
shoots will rise to a height of 2-3 feet. This is a dioecious species, meaning that the sexes are found on separate
plants. When fully flowered, the male-flowered plants will delight us with a
display of hanging purple and gold tassels (stamens whose pollen is dispersed
by the wind). The flowers on the nearby female plant are really only
conspicuous once they have produced fruits.
 | |
| Trout lily leaves |
The large patch of the Dimpled
trout lily has leafed out beneath the large tulip tree.
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| Shooting star |
We were all very excited to see several Shooting star plants with an abundance of flowers in an umbel
gracing the tops of the tall, slender, leafless stems. At the base of the
stems, there is a rosette of spoon-shaped leaves. These are among the most
dramatic of spring ephemerals, with their brilliant white flowers, hanging
downward with their five petals thrown backwards to present the visual effect
of motion, thus the “shooting star.” The
scientific name Dodecatheon means
twelve gods in Greek and was conferred by Pliny who believed that the Primrose
family, of which shooting star is a member, was under the care of the twelve
main Greek gods.
 | |
| Cut-leaf toothwort |
Just beyond the shooting stars, we saw several examples of Cut-leaf toothwort blooming, with their
pale pink or white flowers.
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| Common blue violet |
Common blue violets were visible just about everywhere we
looked.
 | ||
| Dwarf pawpaw terminal leaf bud and flower bud |
 | |
| Dwarf pawpaw flower buds opening |
The warm weather has caused the flower buds of Dwarf pawpaw to swell and develop. The
flower buds are enclosed in hairy, bronze-colored scales that protect the
flower from drying and freezing during the winter. New vegetative growth
(leaves and stems) are not enclosed in bud scales and really only amount to a
tiny, brown, sharply pointed, undeveloped leaf on an even tinier future stem.
They are also minutely hairy, the hairs providing the only form of protection
from winter’s cold and drying winds.
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| Golden ragwort young flower shoot |
 | |
| Golden ragwort flowers |
Golden ragwort is present over much of the Dunson
Garden and has just begun to bloom. There were many plants sporting numerous
purple-colored buds. The purple color is due to the presence of anthocyanin, a
compound present in many plants, such as cross vine, that acts as a natural
“sunscreen,” protecting tender young leaves and flower buds from damage from
the sun. There were a few plants that had fully opened flower heads atop their
flower stems.
 | |
| Wild ginger immature flower buds |
Wild ginger leaves of various sizes and color are
scattered about the Dunson Garden. Linda and Don began pulling back the leaf
litter to look for the flowers, called “little brown jugs.” These flowers rest
at ground level and are covered by dead tree leaves and the plant’s own
evergreen leaves. We didn't find any “jugs” but we did find several white to
cream-colored buds that resembled tiny bowling pins or, as some think, little
pigs. One of the questions that arises from having flowers buried beneath leaf
litter is what pollinates them. An interesting article on the controversy
surrounding wild ginger pollination can be found here. A short summary: they
self pollinate.
 | |
| Alleghany spurge male and female flowers |
Just beyond the Georgia dwarf trillium is a large patch of
the sprawling Allegheny spurge with
large, mottled, evergreen leaves. Linda walked out into the patch and began
looking to see if any flowers were hiding under the leaves. Several male and
female flowers were found, in spikes 1 – 2 inches long; they may elongate up to
4 inches as spring progresses. Once fully developed, these spikes will give off
a sweet fragrance that can be detected many feet away. The female flowers are
found at the base of the spike and consist of 2-4 reddish to white bracts and a
white stigma and style. The rest of the spike consists of many male flowers
that consist of 4 white bracts and 4 – 7 stamens. Neither female nor male
flowers have sepals or petals. Since the flowers are buried under leaf litter
and the plant’s own evergreen leaves, there is still some question about how
they are pollinated (just as with the flowers of wild ginger). The Japanese species of Pachysandra is a rapid spreader, making
it popular as a commercial ground cover. Our native Allegheny Spurge spreads at
a much slower rate and, though much more attractive than the Asian species, has
not found a niche in the ground cover market. The Japanese species is also
budding at this time in the Shade Garden; its flowers are held above the leaves
in short but conspicuous spikes.
 | |
| Seersucker sedge male and female flowers |
We found several plants of Seersucker sedge in flower. Like most sedges in the genus Carex, the male flowers are held in
spikes at the top of the flowering stalks, with the female flowers in spikes
lower on the stalk. The male and female flowers mature at different times to
prevent self-pollination. It gets the name seersucker sledge from the pleated
appearance of the leaves.
The mature leatherwoods
are about to finish blooming for the season. We found only a few flowers on the
shrubs, with fruit starting to appear. Leatherwood has been spreading dramatically
in the Dunson Garden the past several years. Some ramblers pointed out several clumps
of densely packed, short, green woody stems of young leatherwood sprouts
arising from the rhizomes that run rampant through the Garden.
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| Spicebush female flowers |
 | |
| Spicebush male flowers |
Spicebush is now flowering. Spicebush is another
dioecious plant, with individual shrubs being either male or female. Only the
female plants will bear the bright red fruits later in the summer.
Running pine
(Southern) Running
pine (aka Common Running-cedar) is found along the base of the hill in the
lower section of the Dunson Garden. It is an ancient plant that reproduces by
spores, dating from the time of the dinosaurs and before the evolution of
flowering plants.
We were also fortunate to see the first bloom from one of
the two Atamasco lily patches in the
garden.
 | |
| Virginia blue bells |
Virginia bluebells are beginning to bloom, with their
pink buds and blue, fully opened flowers both present on each plant. In the
next week or so, the Virginia bluebell plantings should be awesome.
Kidney-leaf buttercup.
On a quick jaunt down to the river to look for yellow
fumewort, Don didn't find any Fumewort but did find kidney-leaf buttercup in
bloom on the Orange Trail.
SUMMARY OF OBSERVED SPECIES:
Ginkgo tree
|
Ginkgo biloba
|
Red maple
|
Acer rubrum
|
Bottlebrush buckeye
|
Aesculus parviflora
|
American hazelnut (filbert)
|
Corylus americana
|
Chattahoochee trillium
|
Trillium decipiens
|
Eastern spring beauty
|
Claytonia virginica
|
Early meadow-rue
|
Thalictrum dioicum
|
American (Yellow) trout lily
|
Erythronium americanum
|
Sweet Betsy trillium
|
Trillium cuneatum
|
Trailing trillium
|
Trillium decumbens
|
Painted buckeye
|
Aesculus sylvatica
|
Shooting star
|
Dodecatheon meadia
|
Cut-leaf toothwort
|
Cardamine laciniata
|
Common blue violet
|
Viola sororia
|
Dwarf paw paw
|
Asimina parviflora
|
Golden ragwort
|
Packera aurea
|
Leatherwood
|
Dirca palustris
|
Wild ginger
|
Hexastylis arifolia
|
Dwarf trillium
|
Trillium pusillum
|
Allegheny spurge
|
Pachysandra procumbens
|
Seersucker sedge
|
Carex plantaginea
|
Spicebush
|
Lindera benzoin
|
Running pine
|
Diphasiastrum digitatum
(= Lycopodium digitatum) |
Atamasco lily
|
Zephyranthes atamasca
|
Virginia bluebells
|
Mertensia virginica
|
Kidneyleaf buttercup
|
Ranunculus abortiva
|
Japanese aucuba
|
Aucuba japonica
|
