Expand<\/a><\/p>\nThe plant can reach up to 10 feet tall, but its real strength lies below the surface. Knotweed spreads through an interconnected network of rhizomes, underground stems that store energy and regenerate each spring. Even small fragments of these rhizomes can form new plants, allowing knotweed to establish quickly and persist for years.<\/p>\n
\u201cIt really likes streambanks and ditches close to water. Stormwater breaks up those underground rhizomes and carries bits downstream. They get jammed someplace, and then they\u2019ll start a new plant,\u201d said Tim Abbey, a horticulture educator with Penn State Extension\u2019s Green Industry Team.<\/p>\n
Knotweed often appears in concentrated pockets, particularly along steep slopes and creek corridors.<\/p>\n
\u201cIt gets so thick, it\u2019s like being in the jungles of Japan. It grows tall and dense, and once it takes over a hillside, you can barely walk through it,\u201d said Ross Mullin, owner of Mullin Lawn & Garden Care in Pottsville.\u200b<\/p>\n
Knotweed\u2019s dense canopy creates a monoculture, crowding out nearly all native vegetation. Its thick stems and broad leaves block sunlight, preventing other plants from establishing.<\/p>\n
\u201cIf I can grow eight feet tall, I can shade out anything below me,\u201d Abbey said. \u201cAnd I\u2019m not aware of any animal that actually eats the foliage, so there\u2019s no nutritional value for native wildlife.\u201d<\/p>\n
Along streambanks, knotweed provides poor erosion control compared to native vegetation. Over time, its presence can degrade aquatic habitat and water quality. Penn State Extension notes that knotweed infestations can reduce biodiversity, impair water quality and damage infrastructure.<\/p>\n
Effective strategies for managing knotweed<\/p>\n
Removing Japanese knotweed is far more difficult than most homeowners expect. Disturbing the soil, especially by digging, often makes the problem worse.<\/p>\n
\u201cYou can\u2019t really dig it out because digging just fractures the rhizomes. If you take sections of the rhizome and dump them somewhere else, that\u2019ll spread it too,\u201d Abbey said.<\/p>\n
Cutting stems also fails to kill the plant. Both the rooted stem and the trimmed portion can regrow if they contact moist soil.<\/p>\n
\u201cYou can treat it, you can cut it, but if even a little bit of that root system is left behind, it\u2019s going to come right back,\u201d Mullin said.<\/p>\n
Because knotweed is a perennial, control requires multiple years of consistent management.<\/p>\n
Abbey said the most reliable approach combines repeated mowing to weaken the plant with targeted herbicide treatments later in the season, when knotweed is sending energy downward into its rhizomes for the next year. Treatments applied during this window move into the underground system and help kill the source of regrowth.<\/p>\n
\u201cIt takes a lot of effort, time and money to actually get rid of it,\u201d he said.<\/p>\n
For residents looking to learn more about identification and long\u2011term control, Penn State Extension is hosting a virtual webinar on Japanese knotweed on Friday, Aug. 7 at 1 p.m. Details and registration are available through Penn State Extension.<\/p>\n
\u200bA growing challenge for Pennsylvania<\/p>\n
Knotweed\u2019s persistence mirrors a broader challenge facing Pennsylvania\u2019s landscapes.<\/p>\n
As invasive plants continue to spread, they displace native vegetation, weaken streambanks and strain local ecosystems.<\/p>\n
Knotweed is only one example of how quickly non\u2011native species can take hold, and how important early action is.<\/p>\n
\u201cIf you notice something on your property that\u2019s manageable \u2014 knotweed, stiltgrass, lanternflies \u2014 you should try to control it so it doesn\u2019t continue to spread,\u201d Abbey said. \u201cIt\u2019s a very serious issue.\u201d<\/p>\n","protected":false},"excerpt":{"rendered":"Sprawling patches of Japanese knotweed are choking creekbanks and roadsides all over Northeastern Pennsylvania this summer, highlighting the…\n","protected":false},"author":2,"featured_media":60424,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[2],"tags":[1729,14032,8,17,2164,173,14789,39279,39280,149,39278],"class_list":["post-60423","post","type-post","status-publish","format-standard","has-post-thumbnail","category-japan","tag-environment","tag-home-and-garden","tag-japan","tag-japanese","tag-local-news","tag-news","tag-pennsylvania","tag-pottsville","tag-schuylkill-county","tag-things-to-do","tag-top-stories-stt"],"_links":{"self":[{"href":"https:\/\/www.europesays.com\/japan\/wp-json\/wp\/v2\/posts\/60423","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.europesays.com\/japan\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.europesays.com\/japan\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/japan\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/japan\/wp-json\/wp\/v2\/comments?post=60423"}],"version-history":[{"count":0,"href":"https:\/\/www.europesays.com\/japan\/wp-json\/wp\/v2\/posts\/60423\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/japan\/wp-json\/wp\/v2\/media\/60424"}],"wp:attachment":[{"href":"https:\/\/www.europesays.com\/japan\/wp-json\/wp\/v2\/media?parent=60423"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.europesays.com\/japan\/wp-json\/wp\/v2\/categories?post=60423"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.europesays.com\/japan\/wp-json\/wp\/v2\/tags?post=60423"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
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