Japanese Knotweed blooming on Swamp Road, Worcester Co., Maryland (8/31/2013).

View Record Details Photo by Bill Hubick MBP List

$An invasive species of concern in Maryland. Photographed here in Worcester Co., Maryland (6/17/2012). Brought to England as an ornamental species in 1825 and then introduced to the U.S. <a href=\'http://www.mdinvasivesp.org/archived invaders/archived invaders 2009 09.html\' target=\' blank\' class=\'darkerText\'>Read more</a>. (Photo ID: 1328 - Psn: 10)$

An invasive species of concern in Maryland. Photographed here in Worcester Co., Maryland (6/17/2012). Brought to England as an ornamental species in 1825 and then introduced to the U.S. Read more.

Photo by Bill Hubick MBP List

Japanese Knotweed in Allegany Co., Maryland (8/30/2014).

View Record Details Photo by Kimberly Booth MBP List

Japanese Knotweed in bloom along Potomac River near Sideling Hill Creek, Washington Co., Maryland (8/19/2012).

Photo by Richard Orr MBP List

Japanese Knotweed flowering in Charles Co., Maryland (8/26/2009). Invasive.

Photo by Kerry Wixted MBP List

Japanese Knotweed in Caroline Co., Maryland (8/28/2016).

View Record Details Photo by Wayne Longbottom MBP List

The prolific seeds of the invasive Japanese Knotweed in Caroline Co., Maryland (9/22/2012).

View Record Details Photo by Jim Brighton MBP List

Japanese Knotweed blooming in Montgomery Co., Maryland (8/19/2014).

View Record Details Photo by Elizabeth Miller MBP List

Japanese Knotweed in Anne Arundel Co., Maryland (8/31/2017).

View Record Details Photo by Bill Harms MBP List

Japanese Knotweed in Dorchester Co., Maryland (7/31/2016).

View Record Details Photo by Wayne Longbottom MBP List

Japanese Knotweed in Montgomery Co., Maryland (6/5/2014).

View Record Details Photo by Elizabeth Miller MBP List

Japanese Knotweed in Harford Co., Maryland (4/12/2018).

View Record Details Photo by Josh Emm MBP List

Japanese Knotweed in Caroline Co., Maryland (9/11/2016).

View Record Details Photo by Wayne Longbottom MBP List

Japanese Knotweed in Caroline Co., Maryland (9/4/2016).

View Record Details Photo by Wayne Longbottom MBP List

Japanese Knotweed in Anne Arundel Co., Maryland (6/18/2011).

View Record Details Photo by Bill Harms MBP List

Early spring growth of Japanese Knotweed at Governor Bridge Natural Area, Prince George's Co., Maryland (4/13/2013). Seek and destroy.

View Record Details Photo by Bill Hubick MBP List

Japanese Knotweed in Garrett Co., Maryland (4/21/2017).

View Record Details Photo by Matt Tillett MBP List

Japanese Knotweed in Howard Co., Maryland (5/22/2013).

View Record Details Photo by Joanne Solem MBP List

Japanese Knotweed in fruit in Anne Arundel Co., Maryland (12/24/2018).

View Record Details Photo by Matthew Beziat MBP List

Japanese Knotweed in Allegany Co., Maryland (4/17/2019).

View Record Details Photo by Kimberly Booth MBP List

New Japanese Knotweed shoots in Howard Co., Maryland (3/28/2016).

View Record Details Photo by Nancy Magnusson MBP List

Japanese Knotweed in Calvert Co., Maryland (11/5/2016).

View Record Details Photo by Bill Hubick MBP List

Japanese Knotweed (winter aspect) in Harford Co., Maryland (12/6/2015).

View Record Details Photo by Bill Hubick MBP List

Japanese Knotweed near Lost Lake in Baltimore Co., Maryland (3/27/2016).

View Record Details Photo by Bill Hubick MBP List

Japanese Knotweed in Howard Co., Maryland (Date obscured). (c) johnbotany, some rights reserved (<a rel='license' href='http://creativecommons.org/licenses/by-nc/4.0/'>CC BY-NC</a>). (Photo ID: 332920 - Psn: 165)

Japanese Knotweed in Howard Co., Maryland (Date obscured). (c) johnbotany, some rights reserved (CC BY-NC).

View Record Details Photo by John Hall MBP List

Japanese Knotweed blooming in Howard Co., Maryland (9/13/1981).

View Record Details Photo by Robert Solem MBP List

Japanese Knotweed in Baltimore Co., Maryland (6/8/2019). (c) rroberts6204, some rights reserved (<a rel='license' href='http://creativecommons.org/licenses/by-nc/4.0/'>CC BY-NC</a>). (Photo ID: 263424 - Psn: 200)

Japanese Knotweed in Baltimore Co., Maryland (6/8/2019). (c) rroberts6204, some rights reserved (CC BY-NC).

View Record Details Photo by rroberts6204 via iNaturalist MBP List

Japanese Knotweed in Prince George's Co., Maryland (6/19/2019). (c) agelb, some rights reserved (<a rel='license' href='http://creativecommons.org/licenses/by-nc/4.0/'>CC BY-NC</a>). (Photo ID: 263425 - Psn: 200)

Japanese Knotweed in Prince George's Co., Maryland (6/19/2019). (c) agelb, some rights reserved (CC BY-NC).

View Record Details Photo by agelb via iNaturalist MBP List

Japanese Knotweed in Anne Arundel Co., Maryland (4/24/2020). (c) rfaitoute, some rights reserved (<a rel='license' href='http://creativecommons.org/licenses/by-nc/4.0/'>CC BY-NC</a>). (Photo ID: 290913 - Psn: 200)

Japanese Knotweed in Anne Arundel Co., Maryland (4/24/2020). (c) rfaitoute, some rights reserved (CC BY-NC).

View Record Details Photo by rfaitoute via iNaturalist MBP List

Japanese Knotweed in Baltimore Co., Maryland (5/18/2020). (c) Dwight Johnson, all rights reserved. (Photo ID: 313482 - Psn: 200)

View Record Details Photo by Dwight Johnson MBP List

Japanese Knotweed in Caroline Co., Maryland (6/15/2023). (c) Wayne Longbottom, some rights reserved (<a rel='license' href='http://creativecommons.org/licenses/by-nc/4.0/'>CC BY-NC</a>). (Photo ID: 827251 - Psn: 200)

Japanese Knotweed in Caroline Co., Maryland (6/15/2023). (c) Wayne Longbottom, some rights reserved (CC BY-NC).

View Record Details Photo by Wayne Longbottom MBP List

Japanese Knotweed in Anne Arundel Co. (9/3/2025). (c) Melanie Parker, some rights reserved (<a rel='license' href='http://creativecommons.org/licenses/by/4.0/'>CC BY</a>) (Photo ID: 1347567 - Psn: 200)

Japanese Knotweed in Anne Arundel Co. (9/3/2025). (c) Melanie Parker, some rights reserved (CC BY)

View Record Details Photo by melparker via iNaturalist MBP List

Japanese Knotweed in Prince George's Co. (9/12/2025). (c) Jenny Glenn, some rights reserved (CC BY-NC)

View Record Details Photo by Jenny Glenn via iNaturalist MBP List

Japanese Knotweed in Prince George's Co. (9/12/2025). (c) Jenny Glenn, some rights reserved (CC BY-NC)

View Record Details Photo by Jenny Glenn via iNaturalist MBP List

Japanese Knotweed in Montgomery Co., Maryland (4/18/2026). (c) Jim Brighton, some rights reserved (<a rel='license' href='http://creativecommons.org/licenses/by-nc/4.0/'>CC BY-NC</a>) (Photo ID: 1489239 - Psn: 200)

Japanese Knotweed in Montgomery Co., Maryland (4/18/2026). (c) Jim Brighton, some rights reserved (CC BY-NC)

View Record Details Photo by Jim Brighton MBP List

Japanese Knotweed in Baltimore Co., Maryland (4/12/2026). (c) Adrienne van den Beemt, some rights reserved (<a rel='license' href='http://creativecommons.org/licenses/by/4.0/'>CC BY</a>) (Photo ID: 1494081 - Psn: 200)

Japanese Knotweed in Baltimore Co., Maryland (4/12/2026). (c) Adrienne van den Beemt, some rights reserved (CC BY)

View Record Details Photo by Adrienne van den Beemt MBP List

Map Snapshot

754 Records

GA AL WA FR CL MO HO BA BC HA CE PG AA CV CH SM KE QA CN TA DO WI SO WO

Description

Compare Giant Knotweed, which has cordate (heart-shaped) leaf bases.

Seasonality Summary

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Resources

View at iNaturalist Search Google Images Search MBP Facebook posts

View at Maryland Plant Atlas Search Flora of North America Search Mid-Atlantic Herbaria Consortium Search Norton-Brown Herbarium Search MNPS Facebook posts

Citations

No citations linked for this taxon yet.

MBP marks as "Invasive" any taxon listed in the Maryland Invasive Species Council (MISC) list of Invasive Species of Concern in Maryland. You can read their criteria and review the lists here: https://mdinvasives.org/species-of-concern/. Use of media featured on Maryland Biodiversity Project is only permitted with express permission of the photographer.

Japanese Knotweed blooming on Swamp Road, Worcester Co., Maryland (8/31/2013). View Record Details Media by Bill Hubick.

An invasive species of concern in Maryland. Photographed here in Worcester Co., Maryland (6/17/2012). Brought to England as an ornamental species in 1825 and then introduced to the U.S. Read more. Media by Bill Hubick.

Japanese Knotweed in Allegany Co., Maryland (8/30/2014). View Record Details Media by Kimberly Booth.

Japanese Knotweed in bloom along Potomac River near Sideling Hill Creek, Washington Co., Maryland (8/19/2012). Media by Richard Orr.

Japanese Knotweed flowering in Charles Co., Maryland (8/26/2009). Invasive. Media by Kerry Wixted.

Japanese Knotweed in Caroline Co., Maryland (8/28/2016). View Record Details Media by Wayne Longbottom.

The prolific seeds of the invasive Japanese Knotweed in Caroline Co., Maryland (9/22/2012). View Record Details Media by Jim Brighton.

Japanese Knotweed blooming in Montgomery Co., Maryland (8/19/2014). View Record Details Media by Elizabeth Miller.

Japanese Knotweed in Anne Arundel Co., Maryland (8/31/2017). View Record Details Media by Bill Harms.

Japanese Knotweed in Dorchester Co., Maryland (7/31/2016). View Record Details Media by Wayne Longbottom.

Japanese Knotweed in Montgomery Co., Maryland (6/5/2014). View Record Details Media by Elizabeth Miller.

Japanese Knotweed in Harford Co., Maryland (4/12/2018). View Record Details Media by Josh Emm.

Japanese Knotweed in Caroline Co., Maryland (9/11/2016). View Record Details Media by Wayne Longbottom.

Japanese Knotweed in Caroline Co., Maryland (9/4/2016). View Record Details Media by Wayne Longbottom.

Japanese Knotweed in Anne Arundel Co., Maryland (6/18/2011). View Record Details Media by Bill Harms.

Early spring growth of Japanese Knotweed at Governor Bridge Natural Area, Prince George's Co., Maryland (4/13/2013). Seek and destroy. View Record Details Media by Bill Hubick.

Japanese Knotweed in Garrett Co., Maryland (4/21/2017). View Record Details Media by Matt Tillett.

Japanese Knotweed in Howard Co., Maryland (5/22/2013). View Record Details Media by Joanne Solem.

Japanese Knotweed in fruit in Anne Arundel Co., Maryland (12/24/2018). View Record Details Media by Matthew Beziat.

Japanese Knotweed in Allegany Co., Maryland (4/17/2019). View Record Details Media by Kimberly Booth.

New Japanese Knotweed shoots in Howard Co., Maryland (3/28/2016). View Record Details Media by Nancy Magnusson.

Japanese Knotweed in Calvert Co., Maryland (11/5/2016). View Record Details Media by Bill Hubick.

Japanese Knotweed (winter aspect) in Harford Co., Maryland (12/6/2015). View Record Details Media by Bill Hubick.

Japanese Knotweed near Lost Lake in Baltimore Co., Maryland (3/27/2016). View Record Details Media by Bill Hubick.

Japanese Knotweed in Howard Co., Maryland (Date obscured). (c) johnbotany, some rights reserved (CC BY-NC). View Record Details Media by John Hall.

Japanese Knotweed blooming in Howard Co., Maryland (9/13/1981). View Record Details Media by Robert Solem.

Japanese Knotweed in Baltimore Co., Maryland (6/8/2019). (c) rroberts6204, some rights reserved (CC BY-NC). View Record Details Media by rroberts6204 via iNaturalist.

Japanese Knotweed in Prince George's Co., Maryland (6/19/2019). (c) agelb, some rights reserved (CC BY-NC). View Record Details Media by agelb via iNaturalist.

Japanese Knotweed in Anne Arundel Co., Maryland (4/24/2020). (c) rfaitoute, some rights reserved (CC BY-NC). View Record Details Media by rfaitoute via iNaturalist.

Japanese Knotweed in Caroline Co., Maryland (6/15/2023). (c) Wayne Longbottom, some rights reserved (CC BY-NC). View Record Details Media by Wayne Longbottom.

Japanese Knotweed in Anne Arundel Co. (9/3/2025). (c) Melanie Parker, some rights reserved (CC BY) View Record Details Media by melparker via iNaturalist.

Japanese Knotweed in Prince George's Co. (9/12/2025). (c) Jenny Glenn, some rights reserved (CC BY-NC) View Record Details Media by Jenny Glenn via iNaturalist.

Japanese Knotweed in Montgomery Co., Maryland (4/18/2026). (c) Jim Brighton, some rights reserved (CC BY-NC) View Record Details Media by Jim Brighton.

Japanese Knotweed in Baltimore Co., Maryland (4/12/2026). (c) Adrienne van den Beemt, some rights reserved (CC BY) View Record Details Media by Adrienne van den Beemt.