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.
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| 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
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| 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.
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| Gyro-trac machines mulch shrubs, trees, and stumps to the ground. |
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| 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.
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| Thomas Peters created enormous piles of cut privet trunks, all of which decayed in a year or two. |
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| Within two years of Thomas's work, thousands of Butterweed plants burst into flower in the floodplain. |
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| 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.
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| Aerial view of the right-of-way in 2015 |
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| 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.
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| Silver Plume Grass is flourishing in the newly created Piedmont Prairie in the right-of-way |
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| 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 |
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.
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| 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
