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Dwarf Japanese knotweed
Invasive Species Information
What Is Dwarf Japanese knotweed (Fallopia japonica var. compacta)?
Habitat: Terrestrial. Commonly found along river banks, roadsides, urban areas, waterways and railways. Likes disturbed ground.
Distribution In Ireland: Extensive and widespread
Status: Established
Family name: Polygonacae
Reproduction: Speeds through vegetive means. Fragments of rhizome or stem.
Native to Japan and parts of South East Asia, Dwarf Japanese knotweed is used to extremely harsh conditions. In it's native enviroment it can be found growing on the side of volcanic mountains and has a very hardy perennial growth cycle. Japanese knotweed and it's hybrids are now widely distributed across Ireland causing a major management concern for public authorities and private property owners.
Dwarf Japanese knotweed images
Dwarf Japanese Knotweed - Fallopia japonica var. compacta Flower
Dwarf Japanese Knotweed - Fallopia japonica var. compacta leaves
Dwarf Japanese Knotweed - Fallopia japonica var. compacta flower winter stem
Dwarf Japanese Knotweed - Fallopia japonica var. compacta Flower
Dwarf Japanese knotweed has no natural predators in Ireland and thrives in wet land conditions. It can spread from root fragments left behind when ground is disturbed, which is why it can often be found along waterways and at road sides.
How to Identify Dwarf Japanese Knotweed?
Dwarf Japanese knotweed - Fallopia japonica var. compacta
Colour: Vibrant Green
Leaf: Bright Green, narrow spade shape and leathery
Flower: Pink & white, delicate & small
Stem: Red/purple & green, hollow (similar to bamboo)
Root: Tough, orange/brown with white shoots
Dwarf Japanese knotweed flower leaf & stem
Why Is Japanese Knotweed A Problem?
Japanese knotweed has become a serious problem in Ireland and many other parts of
Europe due to it's aggressive spread and speed of growth causing extensive damage to building and structures.
Having Japanese knotweed can seriously effect the value of properties and prevent the approval of planning permission for site development.
Japanese knotweed Time-Lapse Video
Dwarf Japanese knotweed
Fallopia japonica var. compacta
Dwarf Japanese knotweed is less invasive than Japanese knotweed but can still be a problematic invasive alien species in Ireland for properties, waterways, roads and in wetland habitats.
Knotweed's are classified as one of the top 100 worst invasive species worldwide due to its serious impact on biological diversity, impact on human activity and its capacity to invade new environments.
Dwarf Japanese knotweed Leaf
Knotweed is now widely distributed across Ireland and is a major management concern for public authorities and private property owners.
Dwarf Japanese knotweed flower
New shoots breaking through paving
Once established Dwarf Japanese knotweed can grow at a veracious rate, establishing a root system that can spread up to 7 metres from the plant surface and up to 2 metres down.
The rhizomes (nodes on the plant root) are packed with energy and can remain dormant for up to 20 years!
Dwarf Japanese knotweed is relentless in growing through almost any barrier. It has no problem breaking through weak concrete, brick, paving slabs and tarmac and will push its way to the surface at an alarming rate.
The impact on properties can be devastating.
Dwarf Japanese knotweed can quickly establish dense stands
Dwarf Japanese knotweed Removal
If you discover Japanese knotweed on your property the first thing you will probably do is to try to find out how to get rid of it.
Having Japanese knotweed on your property is enough to strike dread into the heart of any property owner, bearing in mind all the negative media coverage that it has gained during the past few years.
Property buyers and developers have experienced difficulties securing mortgages for properties affected by Japanese knotweed and some lenders reject outright any property affected by knotweed, others take a more practical view and lend where the infestation is being treated.
Japanese knotweed thrives on disturbance and invades environments where soils are routinely disturbed and transported.
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Do not strim, cut, flail or chip the plants as tiny fragment can regenerate new plants and make the infestation harder to control
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Do not attempt to dig out Japanese knotweed, this can actually encourage the plant into growing faster, therefore colonising an area more aggressively
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Do not move or dump soil which may contain plant material as this may also add to its spread
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Do not attempt to pull the plant out of the ground, as this can expose part of the infectious crowns, stimulating growth
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Do not use unlicensed herbicides close to any watercourses, plants or wildlife
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Do not compost any part of the plant, due to the resilient nature of knotweed it could survive and grow on when the compost is ready for use
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Do not dispose of Japanese knotweed in garden waste allotments as this just transports the plant to new locations
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Do not spread any soil that has been contaminated with Japanese knotweed rhizome as new plants will sprout
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Do not do break the law! – Remember, it is an offence if you cause the spread of Japanese Knotweed either intentionally or unintentionally
European Communities (Birds and Natural Habitats) Regulations 2011 non-native invasive plant species A-Z (Updated 2017)
There are currently 35 invasive plant species listed in the European Communities (Birds and Natural Habitats) Regulations (annex 2, Part 1)...
Click on a species from the following list to find out more regarding non-native species subject to restrictions under Regulations 49 and 50.
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American Skunk-Cabbage - Lysichiton americanus
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Red Alga - Grateloupia doryphora