Long-term Experiments in Assisted Migration
Evidence of (1) Thrival and (2) Non-Invasiveness
Evidence of (1) Thrival and (2) Non-Invasiveness
Report by Connie Barlow
• SUMMARY: Based on observations and documentation by Torreya Guardians of "historic groves" (where one or more trees were planted north of Florida before the 1984 designation of Florida Torreya as an endangered species), it is reasonable to conclude that Torreya taxifolia is non-invasive and can thrive in locations substantially north of its peak glacial refuge.
• BACKGROUND: The Torreya Guardians in 2004 were just three: Connie Barlow, Paul S. Martin, and Lee Barnes. We were the original guardians in spirit, but our own planting of seeds and seedlings would begin in earnest four years later, when Jack Johnston joined the team.
A side activity to our own plantings and seed distribution is visiting and documenting historic groves of Torreya trees planted in the first half of the 20th century and well north of the constricted native range in the Florida panhandle.
Only recently have we come to recognize how important it is to document these historic groves. Such groves inadvertently now serve as long-term experiments for determining in northward states:1. whether Florida Torreya can survive (even thrive / naturalize) when assisted in migrating northward.
2. whether Florida Torreya is so well adapted to cooler climates that it morphs from "critically endangered" to "invasive."
PHOTO: Jack Johnston at the century-old Harbison Grove, Highlands NC, 2015.
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• PURPOSE: This page was created August 2018 to highlight how field examinations of historic groves of Florida Torreyas (planted north of its peak glacial range in Florida) confirm that (1) this species can thrive and naturalize in northward states and (2) it will not become invasive if assisted to migrate northward. Accordingly, the writer of this report (Connie Barlow) urges that:The next revision of the official Recovery Plan (2019?) should authorize institutions that have established ex situ plantings in northern Georgia (primarily Atlanta Botanical Garden and University of Georgia) to channel excess seed production to institutions (including land trusts, state or local conservation groups, and garden clubs) for northward plantings and continued monitoring.
A. Naturalized Groves (with healthy offspring)A1. Harbison House, Highlands NC
A2. Biltmore Gardens, Asheville NC
A3. Kennedy Home, Clinton NC
A4. Briarwood Preserve, Saline LA
B. Mature Trees Producing SeedsB1. Bullard Home, Mount Olive NC
B2. Callahan Home, Medford OR
C. Mature Trees Not Producing SeedsC1. Henry Foundation, Gladwyne PA
C2. Spring Grove Cemetery, Cincinnati OH
C3. Chattahoochee River, Columbus GA
C4. Yinger Tree, York PA
List of all EX SITU PLANTINGS (since 1850), 24 pages in PDF, by Paul Camire, 2018.Below is the list of ten groves in northward states interpreted (with photos) on this webpage. in 2018 Paul Camire conducted online research to compile a list of the entire inventory. Click the link above and you will find the 24-page document listing:Note: There are likely many more mature Torreya taxifolia in existence. Over the years there have been many promoters of the species. Burl Turnage, A.J. Bullard, Bill Alexander, Lee Barnes, Jack Johnston and Frank Callahan have distributed seeds/ seedlings widely in order to save the Florida Torreya. After Croom’s discovery of the species in 1833, it became a desired exotic plant at several Victorian-era estates, in the north, from at least 1840. There are bound to be more discoveries of plants in the future, and any additions should be made to this list. Contact the author or Torreya Guardians.
Historic Nurseries that sold Torreya taxifolia: 44 Current Nurseries with occasional inventories for intrastate sale: 9 U.S. government collections: 3 State government / Public Grounds: 6 Private homes / gardens: 23 International Collections: 14 Torreya Guardians seed production (private lands): 2
A. Naturalized Groves (with healthy offspring)
A1. Harbison House, Highlands NC (planted ca. 1920; 6 original trees and >10 seedlings/saplings)
Jack Johnston measures girth, 2015.
• Webpage - Site Visits and History
Because this grove and surrounding regrowth forest was left undisturbed for most or all of the grove's century of growth, it is the best site for studying how this tree grows and reproduces in a wild forest. The overtopping deciduous canopy creates deep summertime shade. Absence of other conifers offers full sun in the leafless months.
Because the trees were planted less than 10 feet from one another, two growth characteristics assist the trees in maximizing photosynthesis: (1) prolific basal sprouts where the trunks face outward from the grove: (2) Lowest branches stretch outward along the ground as far as 20 feet. This suggests the grove may have had full sun originally, but then was overtopped by native Buckeye and Tuliptree, which encouraged the torreyas to reorient growth horizontally.
1. NON-INVASIVE. This century-old grove melded into the forest, with approx. 10 volunteer seedlings and saplings nearby.
2. NEEDS HELP MIGRATING WITH CLIMATE CHANGE. Photo left shows a large sapling 40 yards distant from the parent grove. It is the farthest outlier. Such confirms that this large-seeded tree has very low capacity to migrate with climate change. This may be why the four sister species of genus Torreya all live in mountain habitats where trees can retreat upslope, around to a north-facing aspect, or into a deep shady canyon when climate warms.
3. NATURALIZES EASILY (at 3,300 foot elevation in western North Carolina).
4. NO EVIDENCE OF DISEASE. Site visits by Torreya Guardians in 2006, 2015, and 2017 revealed no discernible evidence of diseased branches on the originals, nor of struggling saplings or seedlings.
A2. Biltmore Gardens, Asheville NC (planted 1929; 9 of 12 originals survive and 9 volunteer saplings)
Michael Dowd measures girth, 2015.
• Webpage - Site Visits and History
In 1939 Chauncey Beadle supplied the Biltmore Estate with a dozen Torreya taxifolia seeds or specimens collected in Florida prior to any understanding of climate change and endangered species. Now this 90-year-old grove and its offspring are precious for securing the wellbeing of the species and for demonstrating that (with little human help) North Carolina is an ideal habitat for escaping the lethality of the diseases of a now too-warm Florida.
Bill Alexander (retired Biltmore Landscape Historian) was the first to advocate (in the 1990s) that Florida Torreya could best be served by moving the species north. He also was the first to donate seeds to Torreya Guardians (via Lee Barnes).
Note: During the 2004 storms, half of the originals were top-damaged by falling White Pine canopy trees; three were removed. Sun-scalding was relieved only when new, UV-resistant leaves grew. Throughout the grove of originals, herbicides were used to remove poison ivy; a thick layer of long-leaf pine needles followed as ground cover.
KEY LEARNINGS:1. BILTMORE TREES SHOW NO SIGN OF INVASIVENESS. The 90-year old grove demonstrates the ability of squirrels to distribute seeds some distance away from the grove (including across the paved road), but numbers and range are far from qualifying as "invasive."
2. TRUNK GIRTH GROWTH MEASUREMENTS: Despite substantial top-damage from two hurricanes September 2004, there is measurable trunk growth between 2006 and 2015 (see the trunk girth chart).
3. BILTMORE TREES WITHSTAND FUSARIUM INFECTIONS. The original (1986) recovery plan for Florida Torreya documents that the canker-forming pathogen has, in fact, been producing non-lethal cankers in the Biltmore Grove since (at least) 1986. (p.3):"There is no doubt in my mind that the primary driver in the mortality of the trees [in Florida] is the pathogen. It is reasonable to assume that it is easily moved around.... We did confirm that the trees at Biltmore Estate in Asheville already are infected, for example ..."Therefore, 32 years of documentation of pathogen non-lethal presence is very strong evidence that the Fusarium blight (whether native or exotic in origin) becomes lethal only when climate deterioration severely stresses the Torreya species and/or strengthens the winter survival or summer pathogenicity of the disease agent."
BARLOW'S RECOMMENDATIONS:1. TEST FOR FUSARIUM AT ALL MATURE GROVES. Forest pathology researchers at University of Florida could instruct Torreya Guardians (or site-specific local institutions) on how to (a) detect Fusarium cankers and (b) collect and send specimens to the UF pathology lab. If the Fusarium is present in other groves of mature trees, but not trending toward lethal consequences, then there is no need at this time to genetically engineer Fusarium resistence into the Torreya taxifolia genome. Genetic engineering (using CRISPR technology) was reported as a recommended next step in March 2018 (following a "Torreya Symposium") here and here. Instead ...
2. ADD ASSISTED MIGRATION TO THE RECOVERY PLAN. There is ample evidence that "assisted migration" into the Appalachian Mountains and other northward regions is the best approach for rapidly moving the species toward "recovery" (hence, de-listing). Historic groves (as reported here) have satisfied "precautionary principle" concerns in that(a) the species is now proven to thrive (and naturalize) in northward states and
(b) the species is non-invasive.
A3. Kennedy Home, Clinton NC (planted 1850s; 1 of 2 originals remain; seedlings are prolific but mowed or weeded out regularly)
Michael Dowd uses stick to knock seeds from sunny
side of mature Torreya tree (31 October 2013).
• Webpage - Site Visits and History
A. J. Bullard (of Mt. Olive, NC) documented this tree and its larger associate in 1995. As many as 5,000 seeds were collected by Bullard from the pair of trees in a single year. In 1998 a storm blew down a long-leaf pine which crushed the larger, sunnier associate.
In 2013 (October 31), Connie Barlow collected fallen seeds and dug up six seedlings (delivered to Jeff Morris). In 2014 Jeff Morris observed more seedlings in distant flower beds. He also noticed that a 6-foot-tall basal sprout had grown from the stump of the old blow-down. Whether or not that basal is a continuing pollen source is unknown; nonetheless, the remaining original tree still produces viable seeds.
The remaining tree is overtopped on the southward side by a deciduous Tilia and a Swamp Chestnut Oak. During the winter a same-size Southern Magnolia (evergreen) blocks much of the southward sunlight.
JEFF MORRIS reported in 2014: " ... There are two 4-ft-tall volunteers that the late Mr. Kennedy moved from under the now-gone tree, and planted in the backyard some years back. It is possible that they provide pollen to the 'fruiting' Torreya. There is at least one additional volunteer about 3-ft-tall along the driveway, bordering a neighbor's property. Finally, we learned that there used to be two additional mature Torreya taxifolia trees, larger than either of the Kennedy's pair, about a block away. They produced fruit for a number of years until the property last changed hands (within the past six years or so). The new owner didn't know what they were, and had them cut down before even occupying the residence. But they likely produced volunteers, even within only a hundred or so feet, in shaded areas. On our next visit, we need to look carefully at prospects in the neighborhood."
1. MONOECIOUS. This tree (as well as the two saplings that Bullard grew on his own property that are offspring of the pair of Clinton trees) provided the first opportunity to document that a single tree can produce both male and female cones. Notably, female cones appear only on branches of the least shady side of the tree (in this case, the northward side, away from the southward neighboring trees).
2. SQUIRRELS CANNOT HARVEST HANGING SEEDS. Early on, Barlow visited Atlanta Botanical Garden and saw the pile of wire cages used to prevent squirrels from harvesting seeds. All the ABG "trees" at the time were rooted branchlets so very short, thick, and shrubby. In contrast, trees grown from seed have droopy long branches with exceedingly sharp needles and the seeds are borne only at the tips (one growing season back). It was evident at the Clinton tree that squirrels had to wait for the seeds to fall. A.J. Bullard reported that having a Swamp Chestnut Oak nearby helped: squirrels preferred the acorns to the torreya seeds.
3. DISCOVERY OF MYCORRHIZAE. Connie delivered seeds and seedlings from her 2013 trip to Jeff Morris. Later, Jeff reported (17 November 2013):"When I was transplanting the six seedlings that Connie gave me on November 3rd, I made an observation that I had not paid attention to before: mycorrhizal root nodules, similar to those I have seen on Cephalotaxus and Podocarpus seedlings in the past. Mycorrhizal root nodules work to facilitate a plant-fungal symbiotic interaction that is vital to the health of the tree. It could also be useful in assisted migration of T. taxifolia, as we seek answers to the 'ideal' place to plant the seedlings.... I have chosen a starter soil mixture that seems to comport with the nitrogen-fixing bacteria and mycorrhizal reactions that help the Torreya taxifolia grow more rapidly."_____
PHOTOS: (1) Seeds ripen to orange and purple, (2) Squirrels remove the fleshy husks, then bury seeds, (3) Volunteer seedling amidst leaves of the neighboring Chestnut Oak and Southern Magnolia.
A4. Briarwood Preserve, Saline LA (planted 1940s or 50s; 1 or 2 originals and several seedlings)
Photo above: NPS ca. 2000.
• Webpage - History and Documentation
3 JUNE 2018, Garrie Landry wrote:There is a very large old specimen of Torreya taxifolia growing at Briarwood Nature Preserve in north central Louisiana. I first saw the tree in the mid 1970s when I was an undergraduate student. At that time I learned it was a male tree. Several years ago I visited the preserve and spent a day with the caretakers who told me that in the last 10 to 15 years this tree began producing female cones as well and ultimately viable seeds. I was shown a number of well-established volunteer seedlings growing near the parent plant. Garrie Landry is Herbarium Curator, University of Louisiana at Lafayette.10 JULY 2018, Rick Johnson wrote:I would love to show you the two mature trees that we have here on the property. One is a seed bearing male which has four seeds on it this year. In addition, I would like to get your input on how to best encourage our seedlings to grow; most are about a foot tall and have been that way for years. Rick Johnson is Curator of the Caroline Dormon Nature Preserve.
Note: Connie Barlow and Clint Bancroft plan to visit (and video-document) the grove in November 2018.
KEY LEARNINGS: We expect major learnings to result from our upcoming site visit. Meanwhile, existing documentation confirms that a specimen that is male in its youth may develop several female branches later in life.
B. Mature Trees Producing Seeds
B1. Bullard Home, Mount Olive NC (grown fr seed ca. 1990; 2 specimens; one or both monoecious)
A.J. Bullard with ripe hanging seeds (31 October 2013).
• Webpage - Site Visit and History
A.J. Bullard (introduced above as early documenter of the Clinton NC trees) planted seeds from the Clinton grove at his home in nearby Mt. Olive. The bushiness of the small-stature trees is notable (both have single trunks, so are indeed grown from seed).
In a 6 December 2013 phone conversation with A.J. Bullard, Connie Barlow learned the history of the two specimens. In approx. 1995 A.J. and his cousin dug up (with the permission of the owner) 75 seedlings that were growing in the unmowed areas around the Clinton NC grove. The seedlings were primarily found along the hedgerows and in the flower garden. He gave away (or traded for other plants to conserve on his property) 73 of the 75 seedlings. He planted just two on his own land, each then about 3 feet tall. He estimates that they probably sprouted from a seed crop around 1988-90.
It is impossible to know whether these two specimens contain significant genes from the tallest (since, blown-down) Torreya on the Clinton NC property, but because A.J. estimates from his 1995 visit that the tallest tree produced about 2/3 of the entire seed crop (of perhaps more than 5,000 seeds from the two trees combined), it is likely that these two specimens contain genes no longer found in the seedlings and seeds that I (Connie Barlow) collected beneath the one remaining (smaller) Clinton Torreya in October 2013. Note: The two seed-producing specimens were surrounded by mowed lawn and neighboring agricultural fields. Thus, even if seedlings might have been started up by squirrels, mowing would have destroyed them. Thus we have no documentation of "naturalization" of offspring at this site.
A.J. Bullard with his two dense, squat Torreya trees. Darlington (Laurel) Oak is visible overhead, now shading the torreys in the late afternoon sun.
1. SUN MAXIMIZES SEED-PRODUCTION BUT SQUAT GROWTH FORM. Connie recalls that these Torreyas had a tall planted oak for a neighbor southward on the lawn, which was the only other tree. Although A.J. said that fox squirrels occupy the tree, I saw none, and there were a lot of very ripe unharvested seeds beneath the torreyas. Thus, from the standpoint of maximizing seed production, the two Mt. Olive trees indicate torreyas can withstand lots of sun, if introduced to sun very early so that a squat, brushy growth form results, rather than a tall growth form. A.J. reported that he watered these two only immediately after planting; no watering in later years which may be an excellent practice to urge this tap-rooted tree to grow its roots deep rather than outward.
2. TIME FOR MATURATION. Seed-grown, with no over-topping canopy neighbors (other than one south-shading tree) documents that it takes 18-20 years for a tree in central (non-mountainous) North Carolina to produce its first seeds.
B2. Callahan Home, Medford OR (2 specimens planted from seeds in 1995); no naturalization is possible, owing to pavement and mowed lawn.
Photo above: Frank Callahan, holding a seed, next to his pair of Florida Torreyas.
• Webpage - Site Visit and History
Torreya Guardians learned of Frank Callahan's pair of Florida Torreya trees in Medford, Oregon, when he contacted us to help him find good homes for a bumper crop of seeds autumn 2016.
In an email to Lee Barnes on 9/29/16 Frank wrote: "We are in the Sunset Garden Book as Zone 7, the trees have survived -6 degrees F. in Medford w/o damage. Both of these trees exhibit male and female 'flowers', which is unusual for this taxon."
Note: This above seed-producing pair is periodically watered and no naturalization occurs because the lawn is mowed up to the trees (with pavement on the other side). The summer dry season and intense sunlight and heat of inland Oregon would likely kill unwatered Torreya trees. However, along the northern coast of California, Torreya californica is found subcanopy usually beneath a year-round evergreen canopy of Redwoods and Douglas-firs.
Sun-scalded leaves of rooted branchlet shrubby torreyas that Frank donated to a city park. Sun-scalding happened because two diseased pine trees (shading south and west) were cut down the previous year.
1. DISCERNING WHEN SUN IS TOO EXTREME. The lower left corner of the photo above shows the most luxurious, biggest-leaved branch of all: It extends under the patio roof (photographer Barlow is standing under that roof), so it never gets any direct sunlight. Both seed-bearing specimens were planted on the north-facing side of the house. The furthest tree from the patio is experiencing sun scald at its top (the summers have gotten super hot and dry in Oregon). Both are also getting scalded where the open west-facing white pavement reflects late-afternoon sun and heat directly onto the trees. Again, this location in full westerly summer afternoon sun has brought forth a very dense, brushy growth form.
PHOTO LEFT shows another cause of sun-scalding: when once-shaded leaves are suddenly exposed to sun. Because the evergreen leaves photosynthesize for 5-7 years, it takes several years for new growth (which adjusts its UV protection to the new light conditions) to green up the tree.
2. CAUTION ABOUT PROLIFIC SEED PRODUCTION. It is well known that tree species under great stress will sometimes produce a bumper crop of seeds (in a final attempt to reproduce vigorously if it senses possible demise.) We'll need to track these trees in future years to learn of their health.
3. CONFIRMATION THAT ROOTED BRANCHLETS WILL NOT YIELD SINGLE-STEM TREES. Frank also planted rooted branchlets in a nearby park. The multi-stem shrubby growth form there confirms that Florida Torreya will not adopt a tree form when derived from a rooted branchlet although some maintain that multi-year vertical staking will eventually yield a single leader.
C. Mature Trees Not Producing Seeds
C1. Henry Foundation, Gladwyne PA (planted ca. 1940-50s); two mature male specimens; no seeds or seedlings
Photo by Paul Camire.
• Webpage - Site Visits and History
The two torreyas on the grounds have been surviving in Pennsylvania since Mary Henry planted them in the 1940s to 1950s. One is believed to have been grown from seeds and the other was brought in as a seedling.
August 2018 Torreya Guardian Paul Camire visited the site. Prior to his visit he did historical research on the site and contacted the site's director (a grand-daughter of the botanist who planted the trees, Mary Gibson Henry). While onsite he also reviewed archived documents.
Both specimens have the growth form of seed-grown main stems, with early basal growth that also went skyward.
Because the trees have taken the tall growth form, only careful scrutiny (with binoculars) would reveal whether any of the full-sun branches are capable of producing female cones. Nonetheless, no volunteer seedlings have yet been discovered in the surrounds (which includes re-growth wild forest).
KEY LEARNINGS: The site is never watered and the specimens are in the company of over-topping deciduous trees (see photo aove). Thus it is in an ideal location for initiating careful observations of how the trees contend with weather conditions in this semi-wild, farthest-north site of fully mature specimens. It would be useful if every autumn, the torreya pair could be scrutinized in quest of a few possible seed-bearing branches.
C2. Spring Grove Cemetery, Cincinnati OH (planted 1962); single shrubby specimen grown from rooted branchlet; male; no offspring.
Torreya Guardian Fred Bess visited tree January 2017.
• Webpage - Site Visits and History
In 2016 the American Forests Champion Tree Register made this Spring Grove Cemetery Florida Torreya specimen the new national champion of the species, following the confirmed death or demise of the previous champion, the Norlina NC tree.
Our Torreya Guardian from Cleveland, Fred Bess, visited the tree January 2016 and concluded:"It seems obvious that it is cutting-grown [not from seed], as it is an oversized bush."
KEY LEARNINGS:1. COLD HARDINESS. This relatively unprotected tree appears to have survived well some gruesome winters. It is therefore important evidence of cold-hardiness. That the "national champion" Florida Torreya is now found in Ohio (previously, the champion tree was in Norlina NC) is yet another indication that assisted migration would serve this species very well.RECOMMENDATION. This tree deserves a female! Because gender cannot be determined in seeds or seedlings, 4 or 5 of seeds/seedlings will need to be planted nearby in order to pair up with the genetics of this tree. From an esthetic perspective, however, planting one or two rooted branchlets clipped from female branches might be ideal. As well, rooted female branchlets will produce female cones much faster than a seedling will.
2. This specimen is registered as male, so if no female cones are ever seen on it, this may suggest the following: Perhaps a tree grown from a rooted branchlet cut from a male branch is incapable of producing any female branches. In contrast, we have good evidence that seed-grown trees are so capable.
C3. Chattahoochee River, Columbus GA (1 male remaining of 3 originals in neighborhood, planted ca. 1890s).
• Webpage - Site Visits and History
Columbus, GA is on the east bank of a free-flowing section of the Chattahoochee River. The Chattahoochee River would have been the key conduit for southward displacement of this large-seeded species from the s. Appalachians during peak glacial times of the Pleistocene.
Until the first decade of the 21st century, three old torreya trees were still found on residential properties in a historically old neighborhood that bordered the river. As of 2015, only one of the three trees still stands. Its top is dead and a huge section of lower bark has been stripped away (lightning?) on the street-side of the tree. Clint Bancroft and Jack Johnston measured the tree in 2016: circumference = 80 inches.
Clint reports: "The owner was aware of his tree's fame and also told me that one of the three original Columbus Torreyas was located in the yard to the right of his house. Although healthy, it was cut down a few years ago by the person who bought the house.
PHOTO left top: In 2015, Connie Barlow and Michael Dowd visited the tree in February 2015. Michael is admiring the old Southern Magnolia in the front yard of this historic house (1892). The Torreya (a male) is visible on the other side of the yard.
PHOTO left bottom: Dr. Kim Coder (Warnell School of Forestry, University of Georgia) published a richly-illustrated pdf of Torreya taxifolia in Columbus, GA. The photo left is captioned, "Male and female trees side-by-side in historic residential neighborhood."
CHATTAHOOCHEE RIVER AS SOUTHWARD CONDUIT & NORTHWARD BARRIER. Standing on the porch (photo left), one sees the lowest branches of the Torreya on the right; Southern Magnolia branches to the left. Across the road is a city park that parallels a free-flowing section of the Chattahoochee River (visible left of the gazebo). Because some ripe Torreya seeds are "floaters" (and remain so for several days in water), the species could have launched seeds into s. Appalachian creeks as the climate cooled, and in only perhaps ten generations established riverside populations all the way to the Apalachicola River in Florida. As the glaciers retreated, however, only squirrels (and perhaps now-extinct giant tortoises) could have helped Torreya move north. Too slow, too far, to return this species to its mountain habitat.
C4. Yinger Home, York PA (one specimen planted in late 1970s from rooted branchlet)
Note: Paul Camire tracked down this information in 2018 and contacted Barry Yinger.
EMAIL RESPONSE FROM BARRY YINGER: "Yes, I planted a Florida Torreya at my farm in York County, PA in the late 1970s. It was given to me by the late nurseryman Tom Dodd Jr. of Semmes AL, who propagated it as a cutting from a plant collected in Florida. Apparently it was a cutting from a lateral branch because it never developed a leader as you see with seed-grown plants.
"My farm was in the cold part of Zone 6 for many years and is now mid-Zone 6 to 6b. However, in January 1994 we had the lowest recorded temperatures ever. It was about -23 F the first night and -12 the next. The high during the day in between was -4 F. I lost a number of trees and shrubs, but the Torreya was not damaged beyond a little discoloration of some of the leaves. I never measured the tree, but after nearly 40 years it was about 20 feet tall and nearly as wide. If it had been rooted from a terminal cutting it would have been a lot taller. As it was, it grew as a big blob. I will try to find a photo for you. I sold my farm in 2016."
KEY LEARNINGS: COLD HARDINESS!