Botany Circular No. 29 Fla. Dept. Agric. & Consumer Services
November/December 1994 Division of Plant Industry
Polygonum perfoliatum L. (POLYGONACEAE), the Mile-a-minute Weed1
J. Douglas Oliver2 and Nancy C. Coile3
INTRODUCTION: Polygonum perfoliatum L. grows so rapidly and thickly that it is called the "mile-a-minute
weed." Other common names include "minute weed", "tearthumb", and in Japan, "ishimi-kawa" (Ohwi 1965) or
"shimakawa" (Cusick and Ortt 1987). Tearthumb is a common name used for several species of Polygonum and
refers to the prickles on the stems and leaves which can tear thumbs and fingers of the unwary. This exotic species
has become established in Pennsylvania and Maryland. It is starting to replace native vegetation, and is on the move
southward. Kartesz (1994) provides one synonym: Ampelygonum perfoliatum (L.) Roberty & Vautier; others include:
Tracaulonperfoliatum (L.) Greene (Reed 1979a and 1979b) and Persicariaperfoliatum (L.) Greene (Cusick and Ortt
So far, this weed has not been found in Florida. However, a look at the spread of P. perfoliatum in the United
States and knowledge about the origin of P. perfoliatum may forewarn us of the risk that this weed poses for the
Fig. 1 (left). Vining habit of Polygonum perfoliatum. Note
prickles on stems and lower surface of leaves.
Fig. 2 (above). (A) Saucer-shaped ochraea and (B) bluish
infructescense. Finger in lower left provides size scale.
Photography credits: Larry H. McCormick, Pennsylvania State
Contribution No. 30, Bureau of Entomology, Nematology and Plant Pathology Botany Section.
2 Biologist, Florida Department of Environmental Protection, Bureau of Mine Reclamation, Tallahassee, FL 32310.
Botanist, FDACS, Division of Plant Industry, P.O. Box 147100, Gainesville, FL 32614-7100.
DISTRIBUTION: Mile-a-minute weed is native to Japan, Korea, China, Taiwan, the Malay Peninsula, India (Ohwi
1965, Reed 1977), and Bangladesh (Kahn and Hassan 1978) and has been recorded from Turkey (Guner 1984). The
first record in the U.S. is a single specimen in Gray Herbarium at Harvard University dated 1890 and taken from
boat ballast near Portland, Oregon (Hickman and Hickman 1977). Hill et al. 1981 cite its presence in British
Columbia, Canada in 1954. Since 1954, there have been no records of P. perfoliatum west of the Rocky Mountains
in North America.
In the East, the story is not as pleasant. The earliest record is a 1946 collection from an orchard in York
County, Pennsylvania. These plants probably originated from rhododendron nursery stock imported from eastern
Asia in the 1930s (Hill et al. 1981). By 1979, P. perfoliatum was established in six counties in Maryland (Riefner
and Windier 1979). The weed continued to spread southward, and by 1981, P. perfoliatum was in West Virginia
(Duppstadt 1981), then Virginia (Bradley 1983), the District of Columbia (Cusick 1986), and in southern Delaware
and New Jersey (N. Hartwig, personal communication).
The first edition (1963) of Gleason and Cronquist's manual of the northeastern US flora did not contain P.
perfoliatum. However, the 2nd edition (1991) cites establishment in Pennsylvania, Maryland, and West Virginia and
indicates that the species is "expected to spread." With the ability to outcompete much of the native flora and the
prickly nature of the plants, this pest species' movement southward could cause it to become a great problem in the
southeastern U.S. The climates of the southeastern U.S. and Southeast Asia have many similarities, and a plant
whose origin is Southeast Asia might well be expected to thrive in the southeastern U.S. Primary means of
distribution are likely transport by avian migration, movement of contaminated soil (e.g., with potted plants or on
machinery), and by hay. When machinery travels over tangled mats of P. perfoliatum, the plants can wrap around
axles and actually impede movement (R. Westbrooks, personal communication).
DESCRIPTION: Polygonum perfoliatum is an annual scandent herb with elongated, branched stems to 2 m long.
Fagan Johnson (personal communication) has seen plants clambering up to 12 feet in pine trees. Stems are slender,
have short retrorse prickles and, when in the sun, may be reddish. Leaves are alternate, simple, triangular, 2.5-7.5
cm (1-3 inches) long and wide; the base is truncate, but with a peltate attachment to the petiole. Leaves are glabrous
except for retrorse prickles on the underside of the leaves, especially on the mid-vein and the vein at the base of the
leaf (Fig. 1). Petioles are as long as leaf blades and have retrorse prickles. Ocrea nodall sheaths which arise from
fusion of stipules) are a diagnostic feature of Polygonum. Rather than the usual tubular and chartaceous ocrea, these
flare widely into a saucer shape and appear leaf-like (Fig 2). The upper leaves are represented by the foliaceous
The perianth parts are greenish-white, 3-4 mm long (ca. 1/16 inch) and at maturity thicken, become metallic-
blue and 5 mm (ca. 1/8 inch) wide and long. Inside the mature perianth is the single, shiny, hard, black, nearly
round fruit (an achene) which is ca. 3 mm wide and long. When heated in a microwave oven, the achenes will
expand like popcorn (R. Young, personal communication). The flowers and fruits are arranged in spike-like racemes
to 2 cm long, subtended by a leaf-like bract (Fig. 2). In fruit, the spike looks like an odd, iridescent-blue blackberry.
MAY BE CONFUSED WITH three native species of Polygonum in the southeastern United States which have
retrorse prickles: P. sagittatum L., P. arifolium L. and P. meisnerianum Cham. & Schlecht. var. beyrichianum
(Cham. & Schlecht.) Meisn. in Mart. (Godfrey and Wooten 1981). Riefner and Windier (1979) compare P.
arifolium, P. sagittatum and P. perfoliatum. Godfrey and Wooten (1981) list P. meisnerianum and P. sagittatum
as present in Florida. In order to distinguish all four species, N. Coile produced the key given below:
Key Distinguishing the Prickly Polygonum Species in Southeastern U.S.
1. Leaves peltate; ocrea flare into saucer-like structures; perianth surrounding mature achenes metallic-blue
S...* .................................................... ......... P. perfoliatum
1. Leaves without tissue around petiole junction; ocrea tubular; perianth surrounding mature achenes not
2. Leaves sessile ............................................... P. meisnerianum
2. Leaves petiolate.
3. Leaves sagittate, prickly on mid-rib below, with pubescent margins ......... P. sagittatum
3. Leaves hastate, without prickles below, pubescent on both surfaces ........... P. arifolium
Radford et al. (1964) state that P. sagittatum is "Often a noxious weed." Plants grow into a tangled mass in
creek bottomlands and the unwary and unprotected (N. Coile) can earn abrasions on ankles. If grasped carelessly,
the skin on thumbs can also be torn.
BIOLOGY: Although an annual in Pennsylvania, if P. perfoliatum enters Florida, plants might become perennial.
The native P. hydropiperoides Michaux, with a range from Nova Scotia to British Columbia and throughout most
of the U.S., is an annual in the cooler parts of its range and perennial in the warmer parts (Tarver et al. 1986). The
weather of the native region of mile-a-minute is relatively wet and warm, similar to the weather of much of Florida.
In the US, the present distribution of P. perfoliatum is in temperate regions, but the weed's sub-tropical to tropical
origins and its spread southward give cause for alarm. If subjected to Panetta's homocline analysis and the computer
program BIOCLIM, the potential range in the US for this exotic species could be predicted more authoritatively
(Panetta and Dodd 1987; Panetta and Mitchell 1991); however, this has not yet been done.
In Pennsylvania, seedlings of P. perfoliatum are established by late April and fruits ripen from September to
November (Hill et al. 1981). The fleshy-covered fruits are suitable for dispersal by birds and rodents (Mountain
1989). The late ripening of the fruits makes the scenario of long distance dispersal likely to occur southward because
of the fall migration of seed and fruit-eating birds such as puddle ducks, marsh waders (rails, etc.), sparrows and
finches (F. Mead, personal communication). Also, since seeds are carried downstream in rivers and streams,
especially during flooding, the site in West Virginia along the Ohio River could be critical to dispersal throughout
many new areas (R. Young, personal communication).
Mile-a-minute weed has been found on roadsides, edges of woods, nurseries, wood piles, fallow fields, clearings,
moist thickets, and ditches (Mountain 1989). Weeds commonly inhabit such disturbed areas. However, this weed
is also found in natural areas such as low meadows, stream banks and sites with abundant litter. Riefner and Windier
(1979) state that P. perfoliatum prefers moist, well-drained habitats. While there is some tolerance to shade, growth
is best in sunny locations (Mountain 1989). Polygonum perfoliatum will grow in either pines or hardwoods where
the canopy cover is less than 60%, but prefers openings in the forest (Johnson, personal communication).
Polygonum perfoliatum is sensitive to freezing. The first hard frost of the season can kill the plants (F. Johnson,
personal communication). Since the plants in temperate climates do not root at the nodes, nor have a persistent
rootstock, new plants must be recruited by germination.
Preliminary studies by Wilbur Mountain (personal communication), using a refrigerator and greenhouse
experiments, indicate that cool and moist treatment is required for germination of P. perfoliatum seeds. However,
Fagan Johnson (personal communication) states that when the seeds are scarified, they will respond to a wider
temperature range. Ingestion of seeds by animals can scarify the seeds; birds migrating southward could transport
seeds that are more likely to germinate than those left behind and unscarified. Johnson also notes that when seeds
are stratified, germination seems to be less successful when temperatures are above 20 C. Stratification involves
placing seeds in moist material and storing the seeds at low temperatures in order to break dormancy of seeds. His
seed bank studies indicate that the seeds are extremely durable, with 99% of those that did not germinate still viable
(indicated by a positive test with tetrazolium blue for live cells ).
If cool temperatures are indeed required for germination, then central and south Florida may not be as threatened
by movement of seed. Care must be taken with materials such as soil which might contain seeds exposed to cool
temperatures before moving to the deep South. North Florida does receive temperatures that might encourage
germination of P. perfoliatum seed and, thus, the weed could possibly become a problem in the future.
Polygonum perfoliatum thrives where forests are clear-cut for timber. This could lead to serious economic
problems for logging companies. Mile-a-minute grows rapidly at about the time young pine seedlings are planted,
and then overtops and shades out the small tree seedlings (W. Mountain, and L. McCormick, personal
Rosellini (1991) states that plants form tangled mats that climb over shrubbery and understory trees, shading out
herbaceous and woody vegetation beneath. Strong plants such as the native Sambucus canadensis L. (elderberry)
and Rubus spp. (blackberries and other brambles) are overgrown and killed by P. perfoliatum (Moul 1948). Even
the weedy exotic affliction to natural areas, Lonicera japonica Thunb. (honeysuckle), is outcompeted by P.
perfoliatum (R. Young, and D. Windier, personal communications).
CONTROL MEASURES: Eradication of this exotic species is the optimal desired outcome. However, eradication
is very difficult, if not impossible, to achieve. We usually speak of "control" or keeping an undesirable species in
check so that it is not as severe a problem as if left alone. Zamora et al (1989) suggest the following steps for
eradicating recently introduced aliens: early detection and reporting, determination of noxious potential, reliable
surveys about current range, understanding of the population biology, and finally, the proper technology for treating
The herbicide, glyphosate, has effectively controlled dense stands of P. perfoliatum on dry land in some
environments (Hill et al. 1981), and the aquatic version of this herbicide should be effective in wet areas. In a
reforestation clear-cut, a late postemergence application of imazapyr killed the plants (Mountain 1989). Hexazinone
was effective for preemergence and postemergence treatments. For preemergence treatment, herbicide must be
applied before germination, which starts around 1 April in Pennsylvania and presumably earlier further south.
Herbicide recommendations are not yet available for Florida.
Mile-a-minute can be controlled by mowing, or cutting with a scythe (Mountain 1989). This mechanical control
must be done before excessive growth and seed set. Removal is practical by rake or hand (gloved) for small
horticultural areas. However, avoid leaving seed which can cause future infestations. Remove dead or decaying
plant mulch material to lessen favorable sites for seed germination.
Numerous insect species feed on P. perfoliatum in Pennsylvania, but they are polyphagic on a number of other
hosts (Wheeler and Mengel 1984). No effective biocontrols are known.
N. L. Hartwig (quoted by Rosellini 1991) sums up the concerns of many: "If we ignore its presence, we may
be creating conditions for full-fledged spread and infestation."
We appreciate the valuable input of many persons, including W.L. Mountain, Pennsylvania Department of
Agriculture, Bureau of Plant Industry; L.H. McCormick and F. Johnson, Forestry Department, Pennsylvania State
University; N.L. Hartwig, Agronomy Department, Pennsylvania State University; D.R. Windier, Biology
Department, Towson State University, Towson, MD; R.W. Young, USDA APHIS PPQ, Seed Examination Facility,
Beltsville, MD; R.G. Westbrooks, USDA APHIS PPQ, Whiteville, NC; G.P. Jubinsky, R.L. Kipker, A.J. Leslie, W.
Bartodziej and M.P. Phillips of DEP, Bureau of Aquatic Plant Management; and W.N. Dixon and B.L. Pope of
FDACS, Division of Plant Industry.
Bradley, T.R. 1983. Flowering plant records from northern Virginia. Virginia Journal of Science 34: 138.
Cusick, A.W. 1986. Polygonum perfoliatum L. (Polygonaceae): A dangerous new weed in the Ohio River valley. Ohio Journal
of Science 86: 3-4.
Cusick, A.W. and M. Ortt. 1987. Polygonum perfoliatum L. (Polygonaceae): A significant new weed in the Mississippi
drainage. SIDA 12: 246-249.
Duppstadt, W.H. 1981. Additions to the vascular flora of West Virginia. Castanea 46: 340-341.
Gleason, H.A. and A. Cronquist. 1963. Manual of vascular plants of northeastern United States and adjacent Canada. D. Van
Nostrand Company, New York, NY. 810 p.
Gleason, H.A. and A. Cronquist. 1991. Manual of vascular plants of northeastern United States and adjacent Canada, 2nd
edition. The New York Botanical Garden, Bronx, NY. 910 p.
Godfrey, R.K. and J.W. Wooten. 1981. Aquatic and wetland plants of southeastern United States, Dicotyledons. University
of Georgia Press, Athens, GA. 933 p.
Guner, A. 1984. A new record for the flora of Turkey, and Campanula latiloba rizeensis, a new subspecies from Anatolia.
Candollea 39: 345-348.
Hickman, J.C. and C.S. Hickman. 1977. Polygonum perfoliatum: a recent Asiatic adventive. Bartonia 45: 18-23.
Hill, R.J., G. Springer, and L.B. Forer. 1981. Mile-a-minute, Polygonum perfoliatum L. (Polygonaceae), a new potential
orchard and nursery weed. Pennsylvania Department of Agriculture, Bureau of Plant Industry, Regulatory Horticulture,
Weed Circular 7(1): 25-28.
Kahn, M.S. and M.A. Hassan. 1978. Taxonomic studies in the genus Polygonum from Bangladesh. Bangladesh Journal of
Botany 7: 21-32.
Kartesz, J.T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. 2nd edition,
2 vols. Timber Press, Portland, OR. 1,438 p.
Moul, E.T. 1948. A dangerous weedy Polygonum in Pennsylvania. Rhodora 50: 64-66.
Mountain, W.L. 1989. Mile-a-minute (Polygonum perfoliatum L.) update- Distribution, biology, and control suggestions.
Pennsylvania Department of Agriculture, Bureau of Plant Industry, Regulatory Horticulture. Weed Circular 15(2): 21-24.
Ohwi, J. 1965. Flora of Japan. Frederick G. Meyer and Egbert H. Walker (eds.). Smithsonian Institution, Washington, DC.
Panetta, F.D. and J. Dodd. 1987. Bioclimatic prediction of the potential distribution of skeletonweed, Chondrilla juncea L.
in Western Australia. Journal of Australian Institute of Agricultural Sciences. 53: 11-16.
Panetta, F.D. and N.D. Mitchell. 1991. Homocline analysis and the prediction of weediness. Weed Research 31: 273-284.
Radford, A.E., H.E. Ahles and C.R. Bell. 1964. Manual of the vascular flora of the Carolinas. The University of North
Carolina Press, Chapel Hill, NC. 1,183 p.
Reed, C.F. 1977. Economically important foreign weeds, potential problems in the United States. USDA, Agricultural Research
Service and Animal and Plant Health Inspection Service, Washington, DC. Agriculture Handbook No. 498. 746 p.
Reed, C.F. 1979a. Tracaulon perfoliatum (L.) Greene in Maryland. Phytologia 43: 219-221.
Reed, C.F. 1979b. Additional notes regarding Tracaulon perfoliatum (L.) Greene. Phytologia 43: 293.
Riefner, R.E., Jr. and D.R. Windier. 1979. Polygonum perfoliatum L. established in Maryland. Castanea 44: 91-93.
Rosellini, L.M. 1991. Speedy new weed poses threat to reforested lands. Pennsylvania State News, August 19.
Tarver, D.P., J.A. Rodgers, M.J. Mahler and R.L. Lazor. 1986. Aquatic and wetland plants of Florida. Florida Department
of Natural Resources, Bureau of Aquatics Plant Management. Tallahassee, FL. 127 p.
Wheeler, A.G., Jr. and S.A. Mengel. 1984. Phytophagous insect fauna of Polygonum perfoliatum, an Asiatic weed recently
introduced to Pennsylvania. Annals of the Entomological Society of America 77: 197-202.
Zamora, D.L., D.C. Thill and R.E. Eplee. 1989. An eradication plan for plant invasions. Weed Technology 3: 2-12.