Four Steps For Controlling An Invasive Tree In West Feliciana Parish, Louisiana

text / photos ©2006-2012 John Siebenthaler
June, 2006 (rev. 04/2008 | 05/2012) info

An Ornamental Nightmare Is Loose In The Landscape Download the Invasive Plant Guide on the control and destruction of invasives, developed by the Hillsborough County Parks, Recreation and Conservation Invasive Species Task Force in response to Florida’s critical problem of introduced plant exotics. Details the proper use of the most effective herbicides, depending on locale and situation. Download LSU Ag Center Forester Brian Chandler’s excellent field study on the efficacy of eight industrial herbicides in killing Chinese parasol. Very helpful for identifying the tree in various stages. Visit TexasInvasives.org for information on CPT and a variety of other plant, insect, and animal threats. The intentional use of CPT is typically in an urban environment — courtyard, backyard or commercial plantings as a fast-growing focal point. Unfortunately it’s a very short leap to the incredibily dense forest takeover that can quickly blanket and suffocate virtually every other understory plant in the woods. The occasional use of this tree isn’t the problem, but rather the source of the problem. Once CPT escapes using a very efficient system of seed distribution helicoptered into any surrounding woodlands, a well refined campaign of stealthy advancement begins. Left unchecked, the plant rapidly multiplies into a full blown invasion that’s difficult to control on a small scale and nearly impervious to modification in larger areas. Fine Gardening magazine explains the difference between aggressive and invasive, and includes a short list of invasives that are spreading out of control throughout the country.

(ST. FRANCISVILLE, LA) The introduction of Firmiana simplex, aka CPT — Chinese parasol tree, or just parasol – in West Feliciana parish is thought to have occurred sometime in the early to mid-20th century. The original source of the non-native hardwood infestation is believed to have started on – or near – Rosedown Plantation.

Factual or not that first innocuous planting, regardless of origin, marked the arrival of an invasive pest whose subsequent destruction of the environment everywhere it’s gained a foothold is astounding. (links)

The tree’s perfect camouflage lets it blend in undetected, rendering the damage invisible until the takeover is complete. When – not if – the tree escapes into the wild there’s little to slow it down.

Little more than half a century later numerous locations throughout the parish have been completely taken over by the aggressive invader, suffocating hundreds of acres of native vegetation and creating a control nightmare in the process.

Once able to recognize the distinctive crown, observers can easily detect the invader. In town, the CPT-infested woods bordering Commerce Street around Sullivan Dental Center and Wyoming Plantation illustrate both the extent of the problem and the extreme difficulty of selectively correcting the situation.

How tough are they? They survived the Hiroshima atomic bomb from a distance of 1.3 kilometers. Comparisons to kudzu are obvious. It’s probable that in a gardening shootout, the landscape strangling vine could emerge as the dominant invasive of the two, but CPTs ability to gain a formidable foothold in a variety of habitats remains impressive.

Setting The Stage

CPT may have once been aggressively planted as a quick source of forest revenue to augment the regional market’s soft and hardwood forestry products. Its growth benchmarks – fast, straight, self-limbing – that are responsible for the nightmare still look at first glance ideal for lumber or, as some recall, a failed pulpwood experiment.

Parasol quickly dominates any habitat it escapes to, and because as lumber it’s worthless — the wood is too light and soft – there’s no immediate reason for culling. This leaves West Feliciana and surrounding parishes suffering from the silent invasion with a super green removal headache unless a commercial value can be discovered. There may be a biological control that could be brought to bear but so far the only organic threat seems to be cottony scale at a young age, which when observed seems hardly to have had much impact. back to top

Seeds of Destruction: What To Look For

This well-adapted pest flowers in spring and early summer. Each bloom forms five fruits that end up splitting open like a leaf after first oozing a brown, tea-like liquid. The leaflike appendage bears multiple seeds that after launching flutter daintily earthward towards a soft landing in our welcoming West Feliciana habitat.

The seeds — unusual in that they’re arrayed around the perimeter of the ersatz leaf (left) — are well designed for widespread aerial dispersal from heights of 50, 60, 70 feet and higher. They drift down or are scattered by wind in overwhelming numbers that easily germinate in massive quantities, rapidly suppressing through sheer numbers even the hardiest plants. For a look at the tree’s growth and appearance characteristics, visit the LSU AgCenter/School of Renewable Natural Resources web site.

Hallmarks of the tree, with it’s signature parasol crown, include fast growing nurseries that quickly form a relentless suffocating canopy just a few inches off the ground. Notice the newly sprouted colony in the photograph at the top of the page. After the seed bearing parent trees were cut down these first-year seedlings germinated as soon as the sun hit them. Left untreated, they grow at a phenomenal rate and upon reaching maturity perpetuate the cycle.

Drought tolerant, this messy deciduous intruder quickly multiplies, becoming so dense in just a few seasons that what from just a few feet away looks like a healthy forest is in fact a single species monosystem, rivaling other despised and horrendously destructive pests like Chinese tallow, Brazilian pepper, and Melaleuca.

They’re Everywhere (You Just Can’t See Them)

Whether as seedlings, saplings or mature trees, they’ve evolved to successfully block light from reaching the forest floor regardless of growth stage, thereby preventing all but a few hardy indigenous species from surviving. A CPT takeover is powered by sheer numerical advantage that kills off most other plant forms by denying them the air, water, sunlight and nutrients necessary for survival.

A Designated Invasive Species

From Savannah west to Austin and Santa Barbara, this pest is recognized nationwide as a major biological threat in varying stages of prohibition and is listed by the U.S. Department of Agriculture as such on the invasive species web site. Unfortunately, Louisiana to date has yet to fully address the horrendous environmental and economic impact of this uncontrolled invader.

It continues to be a recommended landscape species by the LSU Ag Center in its downloadable (pub1622treesLOWRES.pdf) publication Trees for Louisiana Landscapes, as well as numerous other publications, even as the state provides CPT removal grants.

Other notes: native of China, naturalized across the southern United States from N. Carolina west to California, grown as far north as Washington, D.C. and readily available online and from nurseries.

That’s the background. For any successful reclaimation to succeed, mature seed producers need to be totally eliminated, and at nearly twice the commonly stated height of 40 feet and up to two feet in diameter, this can be a daunting, dangerous, expensive, and labor intensive task.

Hide And Seek Parasols escape detection by masquerading as a healthy forest. In the bottom photo, parasols were highlighted with surveyor’s paint, demonstrating how effectively CPT takes over wooded areas.

Our introduction to CPT began in 1999 on eight wooded acres just north of LA-10. Formerly part of historic Rosedown Plantation, we’d explored the property several times and, being unfamiliar with CPT, assumed it was part of a healthy hardwood forest ecosystem.

Natives Under Seige

Throughout the property there were ones and twos of other native varieties: sweetberry, a scattering of various oaks (Shumard, water, laurel, cow), ironwood, and two veteran magnolias. Old growth beech and plenty of sweet gum are the only species existing in any numbers, while patches of silver bell and dogwood manage quite well in the few areas of heavily shaded woods to escape encroachment.

But the overwhelming dominant tree throughout was Firmiana simplex, by the many hundreds of mature trees, thousands of understory saplings, and tens of thousands of seedlings on our acreage alone.

As Floridians new to the Felicianas, we’d been told by the realtor there was side money to be made were we to set up a stand for roadside sales out on the highway. To our continuing dismay we discovered that nurseries throughout the region, both wholesale and retail, still sell CPTs as being ideally suited for residential landscaping.

We quickly recognized the need to tackle the infestation, setting about the task with a lone 16-inch chainsaw, compound lopping shears, and an occasional three-gallon backpack full of herbicide. Make no mistake — once infested the process of clearing or controlling to the point of occasional maintenance is long and arduous. But it can be done. back to top

A Little Spray Goes A Long Way

Thanks to their large leaf area and rapid uptake, CPT is very susceptible to a good herbicide. The yellow foliage in a patch of sprayed seedlings indicates the very effective disruption of chlorophyll cells.

Our preferred procedure to date has been to first cut down mature seed bearing trees, and then spray the seedlings and smaller saplings with a 1.5% (2 oz/gal) Brushmaster® solution combined with a few drops of dish soap added as a surfactant and a few ounces (per 4 gallons) of ordinary rubbing alchohol (isoproponal) as a penetrant. We use the same solution to thoroughly saturate the surface of the cut stumps to insure they’re effectively destroyed. (Click here for the product description PDF.)

Pay close attention when using a chain saw around these unpredictable toothpicks — they can, and will, fall anywhere, anytime, without warning.

This combination herbicide features dicamba, a pre-emerge herbicide that acts as a disruptive growth hormone, and 2,4-D. Although deadly for the parasol it’s use is forgiving of non-weedy grasses that are essential to erosion control. Because it is a pre-emerge herbicide, it should be applied with caution around the roots of desireable trees and ornamentals should they be present. Fortunately, the wide leaves of the parasol are hard to miss and will retain most of the spray being applied. The relatively low dilution rate also minimizes the threat to desireables. Please follow all safety precautions when applying this or any other chemical control.

Delivery is straightforward: a medium to coarse mist from a backpack sprayer applied to the point of runoff. We also spray freshly cut stumps with the same solution, and when liberally applied there is virtually no residual suckering. Spraying the trunks of green bark saplings is especially handy in the ravines and prompts collapse without a trace within a season or two of treatment.

Although Brushmaster’s recommended only for April through August application, we’ve had excellent success regardless of the month. It’s also observed that even at this low concentration, liberal (drenching) spray coverage of any green bark has the desired effects.

The cut surface/basil bark application recommendation for this product is 10 oz/gal-diesel. We haven’t tried it but assume it’s very effective, especially using the hack and squirt technique on difficult terrain. back to top

Chemical Control Issues

We haven’t tried it, primarily because of sourcing, but Grazon® is another combination herbicide containing 2,4-D and the systemic picloram, often used by utilities for controlling brush along transmission lines. It also incorporates a small amount of isoproponal as a penetrant; stumps can rot in as little as six months post treatment.

Both the choices listed above are selective. Non-selective Glyphosate (RoundUp®) is familiar, commonly available, inexpensive in it’s generic form, and popular. But because it kills indiscriminately we’re hesitant to use it, particularly in the ravines where any loss of erosion control leads to negative consequences.

For an easy to understand overview on the implications of agricultural chemical management, visit Ohio State University’s web page on herbicidal properties and uses.

Chop, Saw, Mow, Repeat

Control begins with a chain saw attack on seed sources. I try to section the trees after felling as an aid to decomposition. The trunks are limbed and the debris stacked in piles (when possible.) The more cuts introduced, including a new strategy of slitting the bark lengthwise, the quicker moisture and insects can begin the process of recycling.

Hit ’Em Where It Hurts A back pack sprayer allows precise application to control seedlings and is especially useful on steep slopes where mechanical control isn’t practical. A few days after spraying, impact on second year seedling (above) is obvious.

Mowing and string trimming are very effective for plants in the nursery stage. Parasol bark, though, is extremely tough. We use a DR 5-hp walk behind string (.175mm) mower for manuverability in rough terrain and even that can’t cope with stems above 5/16" or so without stripping out the cord.

We soon added a 15-hp DR Field Mower which has no problem taking on the plant, including saplings up to two inches in diameter using the optional Brush Blade with its much heavier inertia.

Successful control takes more than one pass: there may be new suckering from cut stems, and any seedlings that were sheltered from the spray by the canopy will survive, but their numbers start to dimenish significantly once seed sources are eliminated.

Retreatments — spraying or mowing — will be required over several seasons until the residual seeds are no longer viable, all sources have been destroyed, and all seedlings are dead.

While mature trees (gray bark) require aggresive measures to bring under control, the green bark stage is easily subdued by sawing, cutting, spraying or basil bark treating. Generally one to three inches in diameter, they’re easy to snip using compound lopping shears. Cutting alone, regardless of tree size, needs prompt stump or followup foliar spraying because of the sucker growth that always occurs.

The Science of Parasol Destruction

The prolific and efficient production and distribution of Firmiana seed requires that seed sources be interrupted as the first step in bringing the pest under control. Little is known in this country of the overall characteristics of the plant. Germination rates, viability, life span – there’s just not much literature available for guidance.

The only field study on control was done here in West Feliciana by Louisiana State University’s AgCenter Area (Clinton office) Extension Forester Brian Chandler. Download his excellent 2001 controlled trial that evaluated the hack and squirt seasonal application of eight industrial strength herbicides.

Brian uses his tried and tested hack and squirt method of application to first slash the extremely tough mature bark and then spray a dose of full strength herbicide directly into the wound. With nothing but a sharp hatchet and a squirt bottle full of glyphosate (RoundUp Ultra) he covers ground quickly, allowing the tree’s own hydrology to distribute the chemical from the canopy to the roots for 100% die-off based on a single treatment that can be administered nearly any time of year. (Note: glyphosate is also available as a less expensive Monsanto-branded Honcho 41% solution in 2.5 gallon quantities.) back to top

The Problem Is Clear The photo clearly shows seed distribution in a heavily infested area. Removing the canopy allows thousands of fallen seeds to quickly germinate, while already sprouted seedlings and saplings react vigorously to their sunny new environment. Seedlings, once sprouted, are easily controlled using either spray or mechanical (mowing) methods.

This method is very efficient for treating larger trees, but there is one drawback to hack and squirt. The trees quickly die in place, but don’t decay as rapidly as when felled to the ground. Depending on your situation — and the size and height of your trees — the unpredictability of having 30 to 70-foot tall dead trees overhead, potentially numbering in the hundreds and ready to topple or collapse without warning, may not be a desired environment.

We also know that although the mature trees are dealt a death blow, their progeny will have to be sprayed several times. Doing so among a forest of ready to topple trees may present a problem, as could fire, with so much potential fuel stored vertically like a parade of matchsticks ready to ignite.

Compared to the alternative (chain saw) though, hack and squirt is definitely much safer to administer, easier and faster to apply, less destructive of any adjacent beneficial vegetation, and 100% effective in killing the tree and any subsequent suckers. And it is also effective in delivering the most important first step: immediate and thorough elimination of the seed source. For more details, call the Clinton office.

Benefits? None. None At All

Chinese parasol has that single characteristic common to most invasives: very rapid growth, which all too often is the most favorable trait cited by homeowners when purchasing plants for casual use.

Rotten To The Core Tree at time of cutting (top) and six months later. There was no warning that the trunk was hollow – and extremely dangerous. Suckering will occur if the stump’s not sprayed, although regrowth won’t survive to maturity.

Making matters worse, they’re cheap to buy and easy to transplant. Straight and self-limbing, they’re favorites for ornamental use in courtyard gardens and small space gardening, and have been widely promoted for urban situations. They’re a recommended species in various schools of landscape architecture throughout the country, including LSU, and are even sold in nurseries and garden centers throughout Baton Rouge.

CPT offers no useful habitat for wildlife in terms of nesting, browsing, or other beneficial attributes, and a best guess parasol lifespan in the Felicianas might not be more than 40 or 50 years in the most heavily infested areas.

There is a thought that CPT helps retard soil erosion. In fact it’s a very unstable tree with a propensity for rot and a relatively shallow root system — it’s easy to find trees that have toppled over when not supported by a dense tangle of neighboring parasols to lean on, due to rot or insufficient root support. In fact, the native vegetation it eliminates is much better suited for erosion control.

Interior damage to an outwardly healthy tree is difficult to detect, and the results can be sudden and dangerous. The core of the tree in the photo above was completely hollow, the result of an old wound and opportunistic carpenter ants. Externally, there were no ready indications of any weaknesses in this 40-foot tall intruder growing beside a favorite path.

Why hadn’t it fallen? Because the trademark arrow-straight growth habit and lack of branching makes for an easy balancing act, one that’s quick to fail when high winds and/or unstable (rain saturated) soil become factors. Even when a tree’s been properly notched during cutting and there aren’t any obstructions to hang up on, they don’t always fall as predicted.

Giving Nature A Chance

Over the course of our multi-year campaign to renew the habitat, I’ve cut down hundreds of trees and we’ve sprayed, lopped and mowed tens of thousands of saplings and seedlings. Those efforts are paying off, as diversity responds to fill the void left by the departed parasols.

Not everything is welcome: privet has emerged with a vengeance and we’ve treated the vicious invasive trifoliate citrus with spray as well. But measured against the tenacity of CPT, dealing with the upstart intruders will be like a walk in the, well, woods. back to top