Timeline for Japanese Knotweed Identification

Sarah Sutcliffe

Timeline for Japanese Knotweed

Identification

Winter

Spring

Autumn

Summer

3027576

October (mid-end) October (beginning)

Autumn

September (beginning) September (end)

Timeline for Japanese Knotweed

Identification

Sarah Sutcliffe

During Autumn,

typically October, the

leaves turn orange/

yellow and drop off,

the stem peels and

sheds its purple

speckles to reveal

orange/brown

coloured woody stems

which can remain for

several years. Above

ground it may be

possible to see the top

of the crown stump,

from which next year’s

new growth will

emanate.

November (beginning)

November (end)

Timeline for Japanese Knotweed

Identification

Autumn

3027576

Timeline for Japanese Knotweed

Identification

(be

gin

nin

g)

(m

id)

(

en

d)

Winter

January

(be

gin

nin

g)

(m

id)

(

en

d)

December

Sarah Sutcliffe

Timeline for Japanese Knotweed

Identification

All vegetation has died

back leaving smooth,

hollow woody canes.

Energy from the above

ground material is

trans-located back into

the rhizome system,

stored and lies

dormant throughout

winter.

(be

gin

nin

g)

(m

id)

(

en

d)

February

Winter

3027576

Timeline for Japanese Knotweed

Identification

Spring

March (beginning)

March (end)

April (beginning)

Sarah Sutcliffe

Timeline for Japanese Knotweed

Identification

Spring

April (end)

May

Purple- green shoots

start to emerge in

Spring (March/April)

with rolled up leaves.

When the new leaves

unfurl these tend to

Have a reddish tinge

which soon turns

green.

New shoots from well-

established crowns

have thicker

asparagus-like stalks

3027576

Timeline for Japanese Knotweed

Identification

Summer

June

July

Growth up to around 3m

high, with dense, hollow

jointed stems reminiscent

of bamboo. Stems are

green with purple speckles.

Dense green leaf coverage,

mature leaves measure up

to 120mm in length with

flattened base and pointed

tip, overall are shovel

shaped in appearance.

Sarah Sutcliffe

Timeline for Japanese Knotweed

Identification

Summer

Leaves are arranged

alternately along the stem in

a zig zag pattern. White

flowers appear in August/

September- October in

hanging clusters which are

attached to the end of the

leaf stem. The underground

rhizomes are thick and

woody with a knotty

appearance. When snapped

reveal a bright orange

coloured centre. The rhizome

system may extend to, and

beyond, a depth of 2m and

in worst case scenario,

extend a maximum of 7m,

but more usually extends 2-

4m laterally from a parent

plant. Growth rate can be up

to 40mm per day.

August (beginning)

August (end)

3027576