Leader
for today’s Ramble: Gary
Crider, the Botanical Garden’s invasive plant control technician
Authors
of today’s Ramble report: Gary Crider and Linda
All
the photos
that appear in this report, unless otherwise credited, were taken by Don
Hunter. Some photos were also taken from the internet, with gratitude to the
photographers who make their work freely available to the public through
Wikimedia Commons.
Number
of Ramblers today: 10
Today’s
emphasis: The Garden’s invasive plant removal program
Reading: Gary read two quotes
that sum up the critical importance of controlling exotic species:
“…the two great destroyers of biodiversity
are first, habitat destruction and, second, invasion by exotic species.” E.O.
Wilson
“We
have allowed alien plants to replace natives all over the country. Our native
animals and plants cannot adapt to this gross and completely unnatural
manipulation of their environment in time to negate the consequences. Their
only hope for a sustainable future is for us to intervene to right the wrongs
that we have perpetrated.” Douglas W. Tallamy, Bringing Nature Home: How
Native Plants Sustain Wildlife in Our Gardens
Gary
also read the 1999 Presidential Executive Order 13112 that defined Invasive Plants: “Any plant species
that occurs outside its area of origin and that has become established and can
reproduce and spread without cultivation and causes economic or environmental
harm.”
Show
and Tell: Gary
brought in a specimen of Perilla Mint, one of the invasive plants he
attacks at the Garden. Perilla Mint is also known as Beefsteak Plant because it
is widely used as a culinary herb in Asia, where it is native. It is an annual
that spreads by seed, so killing plants before they go to seed is very
effective.
 |
| Perilla Mint comes in two color forms, green and purple. When green, it can be mistaken for Coleus and, when purple, for the Basil cultivar known as ‘Opal.’ |
Announcements/Interesting
Things to Note:
Gary
introduced his “Dirty Dozen + 2” of Georgia’s Piedmont Invasive Plants. He
noted that although Kudzu is considered to be the Poster Child for invasive
plants in the south it’s not on this list because it rarely spreads by seed and
is not sold in the horticulture trade. And kudzu seldom goes undetected, as it
requires full sun, limiting its ability to hide and proliferate in forest
interiors.
1. 1. Japanese
Stiltgrass (Microstegium vimineum)
2.
Perilla
Mint (Perilla frustescens) a.k.a. Beefsteak Plant
3.
Chinese
Wisteria (Wisteria sinensis)
4.
Chinese
Privet (Ligustrum sinense)
5.
English
Ivy (Hedera helix)
6.
Bush
Honeysuckle (Lonicera maackii)
7.
Autumn
Olive (Elaeagnus umbellata) a.k.a. Deciduous Elaeagnus
8.
Thorny
Olive (Elaeagnus pungens) a.k.a. Evergreen
Elaeagnus
9.
Nandina
(Nandina domestica)
10. Leatherleaf
Mahonia (Mahonia bealei)
11.
Japanese
Knotweed (Polygonum cuspidatum)
12.
Bradford
Pear / Callery Pear (Pyrus calleryana)
Plus two:
Mimosa (Albizia julibrissin)
and Chinaberry (Melia azedarach)
Today’s
Route: We left the Children’s Garden arbor and walked
down into the Shade Garden, then took the road to the powerline right-of-way
(ROW), and then the Orange Trail into the floodplain. We returned to the Children’s
Garden via the Orange Trail Spur to the White Trail and back through the hollow Chestnut Tree.
OBSERVATIONS:
We first visited two of the Garden’s biggest invasive removal success
stories – Chinese Privet removal in the Middle Oconee River floodplain and creation
of a Piedmont Prairie in the middle section of the Georgia Power right-of-way.
Both are landscapes that have been transformed by removal of invasives and are
well on their way to a high level of native species diversity and ecological
functioning.
Middle
Oconee River floodplain
 |
| Chinese Privet turned the Garden’s riverside trails into dark, claustrophobic tunnels. |
Over a period of many decades, the Middle Oconee River floodplain was completely invaded by Chinese
Privet, turning what should have been a species-rich environment into a monoculture so dense that it was impossible for humans to move through it without trails and for other shrubs or herbs to capture any sunlight. Privet removal at the Garden got underway in 2005, when Dr. Jim Hanula and Dr. Scott Horn, Forest Service research scientists, began a ten-year study of privet removal techniques at four sites in northeast Georgia, including one here
at the Garden. Dr. Hanula’s research team established three 5-acre plots in the
Middle Oconee River floodplain on the west side of the powerline ROW, which was
heavily infested with Chinese Privet. One plot served as the control with no
privet removal. In the second plot, privet was cut with machetes and chainsaws
and the cut stump surfaces were painted with herbicide. In the third plot,
privet was removed using a track-mounted mulching machine (Gyrotrac®) followed
by herbicide treatment of stumps. Stump sprouts and seedlings in treatment
plots were sprayed with herbicide a year later.
 |
| Gyro-trac machines mulch shrubs, trees, and stumps to the ground. |
Both
types of treatments were a huge success. Two years later, less than 1% of the area in
the treated plots were covered by privet compared to more than 60% in the plots
that were not treated. The results of the treatments were immediate and
dramatic: butterfly
and bee abundance and diversity nearly tripled and ground-dwelling beetle species diversity was
greatly increased. Native plant species diversity also
increased.
 |
| During their post-treatment surveys, researchers captured 32 species of butterflies, the most common being Carolina Satyr (upper left), Zabulon Skipper (upper right), Clouded Skipper (lower left), and Silvery Checkerspot (lower right). Photos by Judy Gallagher. |
Later privet
control efforts were conducted on the east side of the ROW by Thomas Peters, a
landscape architect student, who used hand tools to cut the privet at ground level and then applied herbicide to the cut stumps and leaves of sprouts.
 |
| Thomas Peters created enormous piles of cut privet trunks, all of which decayed in a year or two. |
 |
| Within two years of Thomas’s work, thousands of Butterweed plants burst into flower in the floodplain. |
 |
| One goal of the Chinese Privet project was to create habitat for native floodplain species, such River Cane. |
Gary concluded that the key to success on both sides
of the ROW was the targeted use of both cut-stump and foliar herbicide applications. Another key to success is that privet seeds are viable for
only one year which reduces the effort needed for long-term control. Privet
seeds are washed into the treated areas during periodic flooding of the Middle Oconee, which will
require ongoing monitoring and control.
Georgia
Power right-of-way
The
middle section of the ROW, between the Elaine Nash Prairie to the north, and the
floodplain south of the road, has undergone extensive change in the last three
years. Initially planted in ornamentals, perennials, and medicinal plants by
Garden staff in the 1970s and 1980s, this five-acre stretch was abandoned in
the 2000s. It became heavily infested with invasive grasses – Fescue and Bermuda – and a wide
variety of invasive exotic ornamentals.
 |
| Aerial view of the right-of-way in 2015 |
 |
| Right-of-way vegetation in 2015 |
Volunteers removed some of the old hardscaping and perennial beds,
and Georgia Power crews removed trees and large shrubs. But the dense sod of
Bermuda and Fescue remained.
In
2019, the Garden received a grant from the Wildlife Conservation Society’s
Climate Adaptation Fund to convert this area into a prairie to demonstrate that grassland restoration is an effective adaptation to climate change in the Piedmont. Walter Bland, a restoration expert, was contracted to do the conversion. Because Bermuda Grass
is notoriously difficult to eradicate, the site was first sprayed repeatedly
with a grass-specific herbicide.
Other non-native and undesirable woody species
and forbs were treated with glyphosate. After herbicide treatment, the native
grasses Broom-sedge and Little Bluestem were planted as both seed and
plugs. Seeds of 26 species of wildflowers and other native grasses were hand-collected
by Garden staff from local populations, grown up, and planted as plugs on the project site.
 |
| Silver Plume Grass is flourishing in the newly created Piedmont Prairie in the right-of-way |
 |
| Ramblers investigating Yellow Indian Grass in the Piedmont Prairie |
Ongoing efforts
Gary has worked diligently to control some of the worst invasive species at the Garden, including eradicating Thorny
Olive, Japanese Bamboo, and Chinese Privet patches throughout the Garden. Areas alongside and surrounding the ADA path and
the Orange Trail
have been recent targets of Gary’s effort to control Japanese Stilt Grass and Perilla Mint at the
Garden.
 |
| Japanese Stilt Grass and Perilla Mint often grow together in damp, disturbed areas |
Japanese
Stilt Grass is an aggressive, non-native annual grass that has been known to
completely replace native ground vegetation in 3-5 years. Over years of experience with this species, Gary has developed a
control method using a very low concentration of a grass-specific herbicide
that kills only Stilt Grass while preserving all surrounding vegetation,
including desirable grasses such as River Oats. We looked at a half-dozen
or more spots along the ADA path and the Orange Trail where Gary had sprayed
Stilt Grass the week before, with wilting or dying Stilt Grass surrounded by
healthy native plants. Ramblers were given this handout detailing pulling, mowing,
and spraying control strategies for Stilt Grass.
The Shade
Garden is home
to several robust plantings of a non-native fern (Mariana Maiden Fern) and an
aggressively spreading Coastal Plain fern (Kunth’s Maiden Fern, Southern Shield
Fern). Gary suggested that, short of removal from the Shade Garden altogether,
their spread into natural areas could be reduced by cutting back the fern
fronds before their spores form.
 |
| Kunth’s Maiden Fern (left) and Mariana Maiden Fern (right) |
A
NOTE ABOUT GLYPHOSATE: None of these restoration success stories would have happened
without the use of herbicides. The safest and most effective herbicide for
invasive plant control is glyphosate, widely known by the brand name Roundup.
This chemical has become the target of anti-chemical hysteria fueled by
ambulance-chasing lawyers and others with a profit or political motive. The many misdeeds of
its corporate creator, Monsanto (now owned by Bayer), have been conflated with
the product itself. There’s a lot to dislike about those companies and their products
and policies, but a lot to like about glyphosate–basically it’s the best and
safest (for humans and the environment) tool available to those of us trying to
restore habitat for native plants and animals. Here’s a good summary of this
conflict by a Nature Conservancy scientist.
Glyphosate is available now from many other sources
than Monsanto/Bayer and under various brand names, e.g. Rodeo, Kleenup, Accord,
Honcho, E-Z-Ject, Jury, Mirage, Protocol, Rattler, Ruler, Silhouette, Glypro,
Glyphomax, and many others. The active ingredient in all these products is glyphosate and (often)
a surfactant, a detergent-like material to help it spread over weed leaves. As
long as it is applied according to label directions, glyphosate is safe for the environment. In fact, it is used in
sensitive habitat by organizations such as The Nature Conservancy due to its
good environmental profile. Herbicides vary greatly in their characteristics,
and it is important to understand these properties so that good decisions are
made.
On a comparative
scale, glyphosate is of very low toxicity to mammals and most other animals. It
kills plants by blocking an amino acid synthesis pathway found only in
plants, not animals. It is not persistent in the environment like organochlorine
insecticides such as DDT. Glyphosate breaks down completely into natural
constituents over time, specifically carbon dioxide, water, nitrogen, and
inorganic phosphate/ phosphoric acid. In temperate climates, glyphosate’s
half-life is about a month. In the soil, glyphosate becomes tightly bound to
clay particles and is therefore inactive during its decomposition. Unlike about
half of all natural or synthetic substances known, which at some dose will
cause cancer in laboratory animals, glyphosate has actually been found to be
non-carcinogenic by world agencies that assess these characteristics.
NOTE: Herbicides
must be used in accordance with the label directions. Always read and follow label directions prior to use.
OBSERVED
AND/OR DISCUSSED SPECIES
Perilla
Mint Perilla frutescens
Chinese
Privet Ligustrum sinensis
Butterweed Packera glabra
Fescue
Grass Festuca spp.
Bermuda
Grass Cynodon dactylon
Broom-sedge Andropogon virginicus
Little
Bluestem Schizachyrium scoparium
Yellow
Indian Grass Sorghastrum nutans
Silver
Plume Grass Erianthus alopecuroides
Thorny
Olive Elaeagnus pungens
Japanese
Stilt Grass Microstegium vimineum
Mariana
Maiden Fern Macrothelypteris
torresiana
Kunth’s
Maiden Fern Thelypteris
kunthii, synonym Pelazoneuron kunthii