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There are a number of ways to identify Japanese Knotweed, although, like any other plant, its shape,
size and colouring can vary dramatically from its description. This sheet acts as a guide to
identifying Japanese Knotweed.
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If you suspect that you have identified the plant, take photographs or leaf samples and please
contact us for it to be verified by an expert.
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LEAVES
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Colour
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Young shoots have curled-up red/purple or light green
leaves with red/purple colouring. 'Lush green' when
mature, healthy and in growing season. Yellowing/
browning of leaves in late autumn/early winter.
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Shape
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Can be described as heart or shield shaped; broadly oval to somewhat triangular.
Size Up to 22cm in length and roughly 2/3 as wide.
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FLOWERS
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Appearance
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80mm-120mm long clusters of small green-white flowers, blooming from late summer to early autumn.
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STEMS
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Appearance
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Bamboo-like, regular, swollen and often red joints, nodes or knots.
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Colour
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Red and asparagus-like when a young shoot. Stems develop throughout the growing season from being supple and green
to brown and brittle. Stems sometimes have characteristic red/ purple specks or spots.
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Size
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Up to 4cm in diameter. Stems grow up to and over 3m in height.
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Structure
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Hollow stems with periodic nodes. Snap a stem off to test this.
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RHIZOME
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Do not disturb the rhizome!
The rhizome is the concentrated energy source which allows
the plant to re-grow each spring and resides under-ground.
Disturbance can slow the eradication process and may spread
the plant.
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SEASONAL APPEARANCES
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General Points
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Plants can produce new shoots throughout the year, even as
the dormancy stage approaches. The following should be
taken as general seasonal appearances, not as a strict rule:
Spring: Young red/purple shoots appear, turning green as
they age. Some plants leaf initially, but others can grow up to
50cm as straight red or green 'rods' before leaves begin to
appear.
Summer/early autumn: Supple green stems with
flowers and large leaves.
Late autumn/winter: Stems turn brittle and brown.
The flowers die and the leaves turn brown-yellow,
eventually falling off.
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Reeve-Tec Membranes Ltd, Unit 7 Eltisley Business Park, Potton Road, Abbotsley, St Neots, Cambridgeshire PE19 6TX, Tel: 01767 677405, Fax 01767 677706 |
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