History & Introduction
In America, the genus Actinidia was extirpated from the continent nearly 80 million years ago due to shifting climates. It was reintroduced in 1877 when Colonel William S. Clark brought hardy kiwi seeds to America from Japan. He planted them at the Massachusetts Agricultural College, now known as the University of Massachusetts. As travel to Asia became more popular, more explorers brought seeds back to America and the plants became more widespread throughout New England and eventually the Northeast, where it was able to thrive even during the cold seasons. The plants were favored for their vines that could be easily manipulated around fences and walls. This was primarily done during the Gilded Age of 1870 until the early 1900’s. Throughout the years, hardy kiwi has become favored as a permaculture/food forest crop, especially recently. This and other intentional plantings of the plant have led to escaped cultivation. Today, the plant is classified as a Tier 2 invasive species in New York listed for early detection and eradication.
Identification & Biology
Hardy kiwi is a member of the Taravine family (Actinidiaceae). Hardy kiwi is a deciduous, dioecious, twining woody vine capable of growing up to 20 feet in a single season, Hardy kiwi is most conspicuous in summer when clusters of fragrant white flowers with dark purple anthers bloom. Leaves are dark green, oval shaped, approximately three to five inches long, and alternately arranged with sharply serrated margins. Leaves may have distinctive red petioles, especially on new growth. Flowers are borne in clusters, emerging in midsummer and are approximately one inch in diameter, pleasantly fragrant, and white to pale green in color, with purple anthers. Fruit matures to oval-shaped, one inch long, green fruits in September to October. For vines to bear fruit, both male and female parts need to be present on the plant. However, there are some cultivars, like A. arguta ‘Issai’ that are self fruiting and don’t require a male to reproduce.
Damage & Concern
Hardy kiwi’s physical characteristics suggest the plant is dispersed primarily by birds and mammals and the horticultural trade. Hardy kiwi is a Tier 2 species listed for early detection and eradication within LIISMA. It is known to be a cause for concern in several states where it is a newly emerging invasive species. On Long Island, it is known to be present in five locations, with Caumsett State Park being the “first in county” observation for Suffolk County. Hardy kiwi can rapidly grow and form dense stands that block sunlight and smother native vegetation, possibly causing serious alterations in the natural communities it invades. A number of sites throughout Vermont, Massachusetts, New York and New Jersey demonstrate the species’ potential to degrade and alter habitat, creating large homogeneous “vinelands.”
Management & Control
Manual or Mechanical Control
Pulling / Digging Up: Not advisable for larger vines. Underground runners are abundant and will rapidly regenerate. Pulling, if done carefully, is an acceptable method of control for smaller vines and seedlings.
Cutting: Cutting is a necessary first step in controlling hardy kiwi vines, however, it will not result in control if not paired with subsequent herbicide treatments. Cut vines are best left in the trees or piled off the ground. Hardy kiwi stem nodes in contact with soil will re-sprout.
Chemical Control
The pesticide application rates and usage herein are recommendations based on research and interviews with land managers. When considering the use of pesticides, it is your responsibility to fully understand the laws, regulations and best practices required to apply pesticides in a responsible manner. At times, the pest you seek to treat may not be on a pesticide label, requiring a 2ee exemption from NYSDEC. Always thoroughly read the label of any pesticide and consult the NYSDEC or a licensed pesticide applicator with questions.
Foliar Spray: Repeat foliar applications of 3% glyphosate spray may be useful on the foliage of large, procumbent vines which are difficult to detach from the soil or cut. (5)
Cut Stump: This is potentially the most effective method of control for hardy kiwi. Apply undiluted glyphosate to cut stumps of larger vines during the growing season.
Basal Bark: Use a 25% solution of triclopyr in oil and apply during dormancy.
Monitoring & Reporting
LIISMA is currently monitoring hardy kiwi as part of our Early Detection and Rapid Response program. As reports of the species are collected, LIISMA is dedicated to delineating and managing any early emerging infestations of the species before they become widespread. Hardy kiwi is currently a Tier 2 species on Long Island, prioritized for early detection and containment.
Your reports matter to us– report the species to iMapinvasives or iNaturalist as soon as you detect it!
iNaturalist is an app and website that can help you record your own observations, identify species, collaborate with others, and access the observational data collected by iNaturalist users. Already using iNaturalist? Join a LIISMA iNaturalist Project to have your invasive species observations automatically uploaded to our projects! Here are some of our projects you can join: Invasive Species in Priority Areas, EDRR Species, LIFERS, Tier 1 Invasive Species, and more!
Want to dive deeper? Check out iMapInvasives to map invasive species like a pro!
Citations
