Hardy Kiwifruit: Invasive Plant? Or Throwback to the Gilded Age?
Posted: March 22, 2013
In 2012, the Massachusetts Audubon Society published an Invasive Plant Pest Alert on hardy kiwifruit, Actinidia arguta, also called "tara vine", strongly urging people not to grow or propagate this plant. The apparently rampant growth of vines had been documented at three particular locations: 1) at Kennedy Park and the Pleasant Valley Wildlife Sanctuary in Lenox, MA where there is significant area covered with large vines that are overtopping trees, plus a population of seedlings nearby; 2) near Stockbridge, MA; and 3) at Coffin Woods on Long Island, NY, where the issue is thought to be a remnant of an estate planting. These sites stand in marked contrast to observations of the behavior of commercial and research plantings in PA, OR, MN, NY, ME and many other locations, where planted specimens have stayed in place and seedlings have extremely rarely germinated from fallen berries. The disparity in experiences with this plant has prompted many questions:
- Is hardy kiwifruit invasive?
- If it is, is its invasiveness a new problem?
- Why is hardy kiwifruit problematic in one location, and not another; and why does this disparity in observations and experiences exist?
- Could hardy kiwifruit become invasive in other locations, given more time?
This article is an attempt to summarize the current state of knowledge and to suggest a clear research agenda for addressing these questions.
1) Is hardy kiwifruit invasive?
Unofficially, there is a lack of consensus on the answer to this question, due to the disparity in observations alluded to above. The official, legal answer to this question currently, however, is "No." An Executive Order 13112, issued Feb. 3, 1999 (Federal Register, Vol. 64, No. 25), established the National Invasive Species Council (NISC) that in turn is guided by the Invasive Species Advisory Committee’s Invasive Species Definition Clarification and Guidance White Paper (ISAC, 2006). As it relates to federal policy, an invasive species must be gauged by the following criteria:
Environmental Harm – “We use environmental harm to mean biologically significant decreases in native species populations, alterations to plant and animal communities or to ecological processes that native species and other desirable plants and animals and humans depend on for survival. Environmental harm may be a result of direct effects of invasive species, leading to biologically significant decreases in native species populations.” (ISAC, 2006, p. 5)
Cultivated Plants – “Plant and animal species under domestication or cultivation and under human control are not invasive species. Furthermore for policy purposes, to be considered invasive, the negative impacts caused by a non-native species will be deemed to outweigh the beneficial effects it provides.” (ISAC, 2006, p. 8)
So far, A. arguta has failed to meet the criteria required for classification as invasive by several non-federal groups as well. When evaluated in 2005, the Massachusetts Invasive Plant Advisory Group placed A. arguta in "Evaluated Plants Not Meeting Criteria", referring to criteria that would have caused it to be classified as invasive, likely invasive, or potentially invasive. However, that was in 2005, and the plant will be reevaluated, as the following statement was found in the same report: "Can form dense stands; evidence needed to evaluate its reproductive ability and potential to establish new populations away from cultivation." (http://www.newfs.org/docs/docs/MIPAG040105.pdf)
The U.S. Forest Service, following evaluation of hardy kiwifruit, placed it in Category 4 "Plants – Local Concern and Monitoring", rather than placing it in Categories 1, 2, or 3 which are "Plants – highly invasive", "Plants – moderately invasive", and "Plants – widespread non-native species", respectively. Further, the Connecticut Invasive Plants Council also evaluated hardy kiwifruit in October, 2012, and did not place it on their invasive plants list when gauging it by the criteria used to determine whether a plant is invasive.
2) If it is invasive, is its invasiveness a new problem?
Hardy kiwifruit is native to eastern Asia, but in the U.S. the species is often referred to as a new crop, since commercial-scale production has been undertaken only in the past 25 years or so. This has led some people to conclude that the invasiveness question is a direct result of recent commercial plantings, but this does not appear to be the case.
Based on geologic fossil evidence, Actinidia were once native to North America and likely were present on various parts of the continent for nearly 80 million years (Late Cretaceous into the Tertiary Period). Fossilized Actinidia seeds have been identified in north-central Oregon (Dillhoff et al., 2009) and in Arctic Canada (Matthews and Ovenden, 1990), where the vines grew in a forest composed of pines, spruce, redwood, and tamarack, at a paleolatitude of 74 degrees (well north of the Arctic Circle). Changes in climate and repeated glaciations during the Late Miocene, Pliocene, and Pleistocene eliminated Actinidia and many other plants from North America.
Regarding more recent history, the hardy kiwifruit species Actinidia arguta was reintroduced to the U.S. from Japan in 1877 by Col. William S. Clark (Anonymous, 1886), who instituted the structure for the Massachusetts Agricultural College (MAC; now known as the Univ. of Massachusetts, or UMass) and served as its third President (http://www.library.umass.edu/spcoll/umarmot/?p=444). In addition to the Japanese seed material brought back by Colonel Clark, additional material was subsequently introduced. Accessions of at least 3 winter-hardy Actinidia species (A. arguta, A. polygama, and A. kolomikta) were brought into the U.S. by plant explorers and established on various estates, in botanical gardens, and in arboretums, including the Arnold Arboretum of Harvard University located in Boston, MA. During the 1880’s and into the 1890’s, there was some confusion and misidentification between A. arguta and A. polygama, as noted by MAC graduate Samuel B. Green (Green, 1892). Initially, most Actinidia vines were grown for their ornamental qualities, and by the 1890’s A. arguta was reported to be a common plant in many gardens: "The genus Actinidia, woody climbers of the Himalayas and eastern Asia, appears in Japan in three species, of which two are exceedingly common, and are conspicuous features of the mountain vegetation. Of these, the largest and most common, especially at the north, is Actinidia arguta; little need be said of this handsome plant, as it is now common and well-established in our gardens, where it grows with great vigor and rapidity, and where it is one of the best plants of its class." (Sargent, 1893; p. 88)
At the time, the use of vining plants to decorate dwellings was very popular. An American Gardening article in 1904 that discusses the use of vining plants includes specific mention of A. arguta: "Vines are indispensable to the proper embellishment of every well-regulated and artistically designed place, and not only should they be on the walls of mansions, but also on the less pretentious dwellings, on fences, arbors, walls, and dead tree stumps, covering them and hiding them from the ravages of time, and rendering the lowly cabin a fit subject for the brush of an artist". (Dallas, 1904). However useful they were, it also was apparent that unmanaged A. arguta plants could be vigorous to a fault. Consider this passage, from the Transactions of the Massachusetts Horticultural Society for the Year 1890, where William P. Brooks, Professor of Agriculture at the Univ. of Mass, Amherst, presented the following information in his discussion "Fruits and Flowers of Northern Japan". "Of that fruit, the Kokuwa (Actinidia arguta) … I presume you have all heard. Much has been written and said about it within the past few years; though, strangely enough from my point of view, it has been urged upon the public attention as an ornamental climber." He then describes its rampant growth, including growth that overtops trees, and then states "Unless looked after far more closely than most will find time for, it will be found to overgrow all desired bounds, to displace eaves spouts and to make itself a nuisance generally by its omnipresence."
A. arguta continues to be mentioned in Transactions of the Massachusetts Horticultural Society. A discussion is presented on ornamental climbing plants and how to use them, including A. arguta (1887); information is presented on suitable propagation methods for A. arguta (1894); an award is given for a Japanese garden that included A. arguta (1908); and further information is presented on how best to propagate A. arguta (1908). Other publications offering advice on growing hardy kiwifruit included Vines and How to Grow Them: A Manual of Climbing Plants for Flower, Foliage by William C. McCollom (1911), as well as Landscape Gardening as Applied to Home Decoration by Samuel Taylor Maynard (1915).
Some who grew A. arguta in the Northeast during this period did not find the vigor to be objectionable or perhaps had selections that were more manageable. Some were quite fond of the plant. This is apparent in the following account written by David Fairchild, a botanist and plant explorer for the USDA who oversaw the Office of Seed and Plant Introduction: "In 1907, we went to Marblehead [Atlantic coast of MA] on vacation, and in strolling around on the rocky point of land – "The Neck" I think it is called, we saw such a charming garden that we wandered into it. We found an old man there. He was disturbed about something and when I introduced myself and asked permission to look around, he unburdened himself of his annoyance. The house painter had just cut in two a wonderful vine of Actinidia arguta which almost encircled the house with its immense twining stems and covered it with dark green foliage. It had been the pride of Mr. Parker's garden for years and I could have wept with him at the catastrophe, for I realized that he was no longer young, and it would be years before it could again be the stunning plant which it had been. We thought it a strange coincidence that we had wandered into the garden of Mr. Charles N. Parker who had long been the President of the Massachusetts Horticultural Society" (excerpt from "The Fascination of Making a Plant Hybrid Being a Detailed Account of the Hybridization of Actinidia arguta and Actinidia chinensis", published in the Journal of Heredity in 1927).
Clearly, A. arguta plants were being grown in various states throughout the late 1800's and early 1900's, including many locations in MA, and were prized for their ability to rapidly cover buildings, with its smooth, green leaves contrasting nicely with the bright, red petioles. We know from historical accounts that the seeds/plants Col. Clark brought back were distributed to the Arnold Arboretum, Michigan State University, and likely to Ames, IA. Further, Actinidia had been introduced to other places in New England. For example, George Buckham Dorr’s Mount Desert Nurseries in Bar Harbor, ME, were selling A. arguta vines in the early 1920's and possibly a decade or two earlier. This genetic material may have originated from the seeds that Clark brought back from Japan, or from C.S. Sargent of the Arnold Arboretum who made a trip to Japan in 1892 (Sargent, 1893). The origin of the material also may have been mainland Asia through the explorations of E.H. Wilson, the collections of which Dorr may have had access to; C.S. Sargent was his step-cousin. Many A. arguta vines were planted in the estates on Mount Desert Island, much of which is now Acadia National Park. In the 1980's, Mark Fulford of Teltane Farm and Nursery collected and propagated cuttings from numerous historically planted vines he encountered on Mount Desert Island. As far as is currently known, the seeds derived from the female vines never went feral, a claim supported by biological survey info from the Acadia National Park survey (Greene et al., 2004) for the identification and distribution of 24 invasive taxa of invasive status within Acadia National Park. A. arguta did not make this list, even though it has been present in many estate gardens dating back to the beginning of the 20th century or earlier.
A. arguta was also reported to have been planted in some of the cottage estate gardens of the Berkshires, near Lenox, MA. Interestingly, the author of the American Gardening article quoted above was Lenox resident John Dallas, who described from his own experience the growing of many ornamental vines including A. arguta and A. polygama in an article titled "The Decorative Quality of Vines" (Dallas, 1904). In another instance: "There is at Lenox, in the Berkshire Hills, a place with the musical name of Fernbrook Farm. It is high on one of the glorious hillsides between Pittsfield and Lenox and reached by a romantic drive through pretty by-roads. The house itself is of white stucco and dark wood and here the eye catches first of all, perhaps, the decorative use of fruit, especially of rich black grapes, as the vines are caught upward above windows of the second story. … Actinidia arguta, the fine creeper from Japan, and our native bittersweet were in evidence here, very much thinned as to branches but full of fruit" (King, 1915).
It is also known that renowned landscape architect Beatrix Ferrand did design work in the Berkshires including for her aunt, Edith Wharton, at her estate “The Mount”. Ms. Ferrand was known to incorporate A. arguta in her landscape-garden designs in various locations across the Atlantic Seaboard (McGuire, 1982; Ferrand and Pearson, 2009); Edith Wharton authored many books, including classics such as The Age of Innocence and The House of Mirth, and also co-authored The Decoration of Houses in 1897 with (http://www.edithwharton.org/).
While so far we have not been able to establish the exact origin and provenance of the A. arguta vines identified in the Kennedy Park site or the Pleasant Valley Wildlife Sanctuary in Lenox, we do know that "E.J. Woolsey of Boston and his brother-in-law John Aspinwall bought most of the mountain land west of Main Street (today’s Kennedy Park) and established the hilltop Cliffwood estate." (http://www.townoflenox.com/public_documents/lenoxma_webdocs/about). Thus, given the historical evidence of known plantings in this area, it is reasonable to suppose that the A. arguta vines could have been first planted on the site anywhere from the 1890’s to the 1920’s (i.e., approximately 100 years ago). In fact, a postcard of the west wing of the Aspinwall hotel - a grand hotel in a nearly mind-boggling sense - from 1912 depicts a well-established plant that resembles A. arguta climbing trees and the building itself (http://commons.wikimedia.org/wiki/File:Hotel_Aspinwall,_Lenox,_MA.jpg). If the dates are correct, this means that the plants could not have been very old, as the hotel was built in 1902. It was destroyed by fire in 1931, and the grounds later became the site of Kennedy Park (http://en.wikipedia.org/wiki/Lenox,_Massachusetts).
3) Why is hardy kiwifruit problematic in certain locations but not others, and why does this disparity exist?
There appear to be at least 4 different possible explanatory factors for these disparate observations:
- plant biology and morphology,
- genetics (interrelated with biology),
- growing conditions including those that favor germination, and
- origin of plant material (i.e. history).
Most clones of A. arguta are either males or females, as the plants are nearly always dioecious. Thus, isolated male or isolated female plants may grow to be large, but cannot multiply sexually. However, the plants can grow along the ground if they can't find a structure to climb (trellis, building, or tree), can tip-root if the tips touch the ground, can root if the stems reach down to the ground (i.e. self-layer), and can cover large spaces over time if growth is left unchecked. Generally, in cases where single plants remain, such as sites where cottages formerly existed, no offspring are created.
However, a population of plants that includes both male and female plants can potentially set seed, as can the rare hermaphroditic plant. So, if there are seedlings present, there had to be both male and female vines in close proximity, or a hermaphrodite. However, even having male and female plants near each other doesn't mean that viable seeds will result.
There is a huge amount of genetic diversity among different clones of A. arguta, a species which can have either two, four, six, seven, or even eight sets of chromosomes (i.e., multiple ploidy levels) (Kataoka et al., 2010). This places significant limitations on the viable crosses that are likely to take place (Ferguson and Seal, 2008).
Among the species within the Actinidia genus, A. arguta has the greatest geographic distribution in terms of area where they are found in East Asia (Cui et al, 2002). This variation in environment correlates strongly with genetic variation in traits such as flowering time, vigor, and hardiness. Males and females need to have coinciding flowering times, and the same ploidy levels (number of sets of chromosomes) in order for pollination to be expected to effectively take place to produce seedlings that are fertile and not aneuploids (i.e, having an incomplete set of chromosomes). This does not mean, however, that a lack of pollination is guaranteed in all years and cases if ploidy levels and flowering times are different.
Growing conditions, including those affecting seed germination
In general, kiwifruit prefers soils with a high organic matter content; and seed germination, though germination is likely to be enhanced in a high organic media such as a soilless mix, as compared to an agricultural soil (Sale, 2003; p. 19). There also is some indication that passage of seeds through the digestive tract of at least one bird species can accelerate germination and increase the germination rate of Actinidia seed greatly (Logan and Xu, 2006). Even when Actinidia crosses are purposefully made, such as in breeding attempts, germination percentages, even under highly controlled conditions, can vary widely from 0% to nearly 100%.
Origin of plant material (i.e. history)
Although it is implied in the above three factors, it is worth making explicit how important plant origin is to this central question of invasiveness. However "invasive" they appear today, abandoned plantings, allowed to grow unhindered, are easily explained and fail to meet the criteria of invasiveness. It is only in those cases where seeds are known to have been naturally dispersed and germinated that these other factors of biology, genetics, and environmental conditions need to be examined.
What does all this mean for the site(s) where hardy kiwifruit appears to be invasive due to a process of seed dispersal? If indeed they are seedlings, it means that it's likely there was a "perfect storm" situation, where two or more selections of different A. arguta specimens matched in ploidy level and time of flowering co-existed. In addition, conditions had to exist that were conducive to seed germination, possibly including ones that would "prime" the seeds (i.e., induce them to germinate). Further investigation into historical accounts may provide more clues regarding to help explain what is happening in these cases.
4) Could hardy kiwifruit become invasive in other locations, given more time?
A continuum exists for the potential of introduced (or alien) species to become invasive, ranging from benign to extremely aggressive. Most introduced species are not invasive, according to the “Tens Rule”: only 10-percent are likely to become established, and only 10-percent of the established plants are likely to become invasive (Williamson and Fritter, 1996).
If hardy kiwifruit originating from old plantings or specimens are truly invasive, and have a high capacity to disperse in a relatively short time, then these vines should have escaped by now and occupied a much greater area than their present distribution indicates. This is especially notable given that A. arguta has been present in Lenox, MA for more than 100 years based on historical information. Regarding many of the older kiwifruit plants found in surveys, it appears that the vast majority of hardy kiwifruit "finds" surviving on many sites are not recently established invasive plants but rather the botanical headstones of long-lost gardens and cottages. This does not mean, however, that individuals or organizations should stop monitoring them.
In commercial and research plantings across the country, where pollination has been taking place for decades and thousands of pounds of viable seed-containing fruit have been produced per acre, volunteer seedlings have been extremely rare. Logically, what this suggests is that there may be some basic difference in the genetics of the plant material present on problem sites, or possibly some other factors such as habitat fragmentation or degradation that enabled A. arguta to become locally established. For example, this might be due to changes in the soil conditions from burning or from the invasion of earthworms in forest ecosystems, which are linked to a lack of understory growth.
There may well be genetic propensities in material on problem sites that are not present in commercial plantings, reflecting on the fact that the plant material utilized on these sites was likely to have been selected for ornamental characteristics (i.e., the ability to quickly grow to cover cottages and estates) rather than fruit production. Because of these different objectives, it is possible that ornamental material ended up at the Arnold Arboretum in Boston, whereas plants with valuable fruit production characteristics were sent to the USDA in Washington, as plant exploration expeditions continued, as specified in an agreement between the two entities: "By means of a cooperative arrangement between the Bureau of Plant Industry and the Arnold Arboretum, Mr. E. H. Wilson, the well-known explorer of central China, who is in the central provinces of China collecting seeds and plants for the Arboretum, will collect for the Bureau such seeds and plants as are of a purely agricultural character in exchange for material which Mr. Meyer is authorized to obtain for the use of the Arboretum." (Galloway, 1908; p.83). Here, the words "agricultural character" means having characteristics of greater value for fruit production rather than for ornamental purposes. Both Meyer and Wilson conducted extensive plant explorations in parts of China, Korea, Russia, and Japan.
Another possibility is that in commercial production, most of the berries and seed source is removed through harvest, compared to untended vines where the berries could ripen past maturity.
The Path Forward
Ultimately, this issue will be addressed state-by-state and area-by-area, as local individuals and organizations should know what is best for their situations. In all cases, however, local decision-makers will greatly benefit from a more thorough understanding of the "invasiveness" observed at those sites that have been identified as problematic. As suggested by the information collected here, a detailed historical record should be assembled for these sites to better understand the pattern of land-use and factors that would have influenced the magnitude and type of A. arguta growth. Such research will be informative and suggestive, but it will not be conclusive for all sites. To supplement this historic perspective, research needs to be conducted to establish the genetic relatedness of individual plants within problematic populations to each other as well as to known cultivars. It is only through a detailed genetic characterization of this kind that we will be able to say, with certainty, if the intrusions we observe are due to vegetative propagation or seed dispersal. Furthermore, detailed information on site-specific parameters such as bird species involved in seed dispersal, and past or current site disturbances should be gathered. Given the rich history and great economic potential of this species in the region, we urge decision-makers to support these clear avenues of research and postpone considering any changes to the invasive status of A. arguta until such information is gathered.
- Anonymous, 1886. Memoirs - William Smith Clark. Proceedings of the American Academy of Arts and Sciences. V. 13, p. 520-523.
- Cui, Z., Huang, H., and Xiao, X., 2002. Actinidia in China. China Agricultural Science and Technology Press, Beijing. 296 p.
- Dallas, J. 1904. The Decorative Quality of Vines. American Gardening. Vol. 25, No. 485 (May 21, 1904), p. 331-332.
- Dillhoff, R. M., Dillhoff, T. A., Dunn, R. E., Myers, J. A., and Strömberg, C.A.E., 2009, Cenozoic paleobotany of the John Day Basin, central Oregon. In, O’Connor, J.E., Dorsey, R.J., and Madin, I.P., (eds.); Volcanoes to Vineyards: Geologic Field Trips through the Dynamic Landscape of the Pacific Northwest: Geological Society of America Field Guide 15, p. 135–164, doi: 10.1130/2009.fl d015(07).
- Farrand, B., and Pearson, C. M., 2009. The Collected Writings of Beatrix Farrand: American Landscape Gardener (1872-1959). University Press of New England, Lebanon, NH, 226 p.
- Federal Register. Vol. 64, No. 25. Monday, Feb. 8, 1999, Presidential Documents.
- Ferguson, A. R. 1990. 1. The genus Actinidia, p. 15-35. In: Kiwifruit Science and Management, I. J. Harrington and G. C. Wharton (eds). 576 p.
- Ferguson, A. R. and A. G. Seal. 2008. Ch. 8 Kiwifruit, p. 235-264. In: Temperate Fruit Crop Breeding: Germplasm to Genomics, J. F. Hancock (ed.).
- Galloway, B. T., 1908. Report of the Chief of the Bureau of Plant Industry for 1907. United States Department of Agriculture Annual Reports. Washington D.C. 93 p.
- Green, S. B., 1892. Vines and Climbing Shrubs. University of Minnesota Agricultural Experiment Station, Bulletin 24. Saint Anthony, Minnesota. p. 206.
- Greene, C. W., J. E. Weber, S. C. Rooney, and K. B. Anderson. 2004. Invasive Plant Species Distribution and Abundance in Acadia National Park. Technical report NPS/NER/NRTR--2004/003. U.S. Dept. of the Interior.
- ISAC. 2006.
- Kataoka, I., T. Mizugami, J. G. Kim, et al. 2010. Ploidy variation of hardy kiwifruit (Actinidia arguta) resouces and geographic distribution in Japan. Scientia Horticulturae 124:409-414.
- King, L.Y. 1915. The Well-Considered Garden. Charles Scribner's Sons. p. 256-257.
- Kobayashi, M., and T. Kamitani. 2000. Effects of soil disturbance and light level on seedling emergence in a Japanese secondary deciduous forest. J. Veg. Sci. 11:93-100.
- Logan, D. P., and X. Xu. 2006. Germination of kiwifruit, Actinidia chinensis, after passage through Silvereyes, Zosterops lateralis. New Zealand Journal of Ecology, 30(3), 407.
- Massachusetts Horticultural Society. Years – various. Transactions of the Massachusetts Horticultural Society. Accessible online at http://archive.org/details/umass_amherst_libraries
- Matthews, J. V, Jr. and L. E. Ovenden. 1990. Late Tertiary Plant Macrofossils from Localities in Arctic/Subarctic North America: A Review of the Data. Arctic 43(4):364-392.
- McGuire, D. K., 1982. Beatrix Jones Farrand (1872-1959): Fifty Years of American Landscape Architecture. Heritage Printers, Inc., Washington D.C., 147 p.
- Sale, P. R., 1983. Kiwifruit culture. D. A. Williams (Ed.). Wellington,, New Zealand: Government Printer, Wellington. 94 p.
- Sargent, C. S., 1893. Notes on the Forest Flora of Japan. Garden and Forest. v 6 (261) p. 88-89.
- Williamson, M. and A. Fitter. 1996. The varying success of invaders. Ecology 77:1661-1666.
Prepared by Kathy Demchak, Dept. of Plant Science, Penn State University; Bob Guthrie, Volunteer Curator, Univ. of MN Actinidia collection; Iago Hale, Dept. of Biological Sciences, Univ. of NH