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Japanese Knotweed


Amadeus
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Just now, Happier diner said:

I already know. By underground roots but also by flowers and seeds. Otherwise it would be confined to Japan 😁

A small cutting just 2mm x 2mm will grow roots, so never use a strimmer as some builders did down here a few years ago...

Seed - very difficult, also I believe there are no males (so no seeds), just one female which has reproduced from its original home at Kew by cutting.

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4 minutes ago, Happier diner said:

I already know. By underground roots but also by flowers and seeds. Otherwise it would be confined to Japan 😁

??? How do you work that out?

Flowers can never spread a botanical species.

Its extremely unlikely it would spread from seeds.

That leaves, stems, shoots or roots, rhizomes or crowns

Knotweed does not normally spread by seeds. However it can grow from cut stems, crowns or rhizomes: Rhizome fragments of 1cm (0.7g) can sprout a new plant. Stem cuttings from mowing, flailing, or strimming can re-grow and establish new plants.

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Just now, GD4ELI said:

A small cutting just 2mm x 2mm will grow roots, so never use a strimmer as some builders did down here a few years ago...

Seed - very difficult, also I believe there are no males (so no seeds), just one female which has reproduced from its original home at Kew by cutting.

You are right. rhizome so it can spread via bits and shoots. The point being it didn't necessarily come from your neighbours. The second point being there are various ways it can spread

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6 minutes ago, John Wright said:

??? How do you work that out?

Flowers can never spread a botanical species.

Its extremely unlikely it would spread from seeds.

That leaves, stems, shoots or roots, rhizomes or crowns

Knotweed does not normally spread by seeds. However it can grow from cut stems, crowns or rhizomes: Rhizome fragments of 1cm (0.7g) can sprout a new plant. Stem cuttings from mowing, flailing, or strimming can re-grow and establish new plants.

You are being pedantic. It can spread by various ways. That's what makes in invasive.

Take you point though.

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3 hours ago, GD4ELI said:

There was a big effort ~20 years ago to get rid of it in Glen Auldyn, it never got into my mother's garden but was in neighbouring land. A new house was built in Glen Auldyn on land which had knotweed in it, will be interesting to see if it returns.

If the GA midges can't eat JK then nothing will get rid of it :) .


Did the knotweed consume the house?

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5 minutes ago, Happier diner said:

You are being pedantic. It can spread by various ways. That's what makes in invasive.

Take you point though.

And it can stay dormant for decades.

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We have JK on Trebah farm because a farmer took the sediment from a pond in Trebah gardens to use as fertiliser. There had been JK at Trebah gardens many decades ago. The sediment soon started sprouting...
 

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12 minutes ago, Happier diner said:

You are being pedantic. It can spread by various ways. That's what makes in invasive.

Take you point though.

It very rarely seeds in the UK. Even if it does they don’t produce plants, think daffodils, tulips, crocuses, etc.

They only reproduce by seed with intensive horticultural intervention.

So, no, I’m not being pedantic.

You questioned how you could sue as you wouldn’t know where it came from. That’s just not true.

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6 hours ago, GD4ELI said:

Lots of it on a local farm (Trebah, very well known). Impossible to eradicate, comes up through a thick concrete WWII road. If treated incorrectly can actually grow even stronger. It really thrives in the Manx and Cornish climate.

Nonsense. Easy to control, if one knows what they are doing. It does not grow through concrete - another urban myth... it grows through cracks in concrete, as a significant amount of plants are able do.

The biggest issue with Japanese Knotweed is the scaremongering that is a byproduct of misinformation.

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2 hours ago, Out of the blue said:

I had a large patch of knotweed on some land I purchased. Glysophate treatment in the late Autumn about flowering time knocked out 99% of the visible knotweed, and spot weed killer on the emerging shoots during the subsequent growing seasons has seen a year on year decrease to virtually nil. After a while it is quite easy to spot the pattern of roots from the position of the red shoots and virtually anticipate where they will pop up. It is a variety of bamboo that was imported in the 1800’s because it was pretty (that worked out well). It does need to be controlled as it is invasive and will run riot, but I have found it relatively easy to manage, and frankly the fear and hype about damage and the over the top sensationalism of the red tops make me think of a virus beginning with C.

Quite possibly the most rational post I have seen on MF. 

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Posted (edited)
53 minutes ago, Happier diner said:

I already know. By underground roots but also by flowers and seeds. Otherwise it would be confined to Japan 😁

Sorry, incorrect - seed is not a consideration.

Deposition of fragmented material is the main vector for spread.

Edited by Tricky
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32 minutes ago, Tricky said:

Nonsense. Easy to control, if one knows what they are doing. It does not grow through concrete - another urban myth... it grows through cracks in concrete, as a significant amount of plants are able do.

The biggest issue with Japanese Knotweed is the scaremongering that is a byproduct of misinformation.

Not quite true, some JK has been know to sit dormant in rainforests for 50-60 years and then, when woken, attack the nearest living thing and deny that WW2 is over...... 

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14 minutes ago, Boris Johnson said:

Not quite true, some JK has been know to sit dormant in rainforests for 50-60 years and then, when woken, attack the nearest living thing and deny that WW2 is over...... 

This is because 50 or 60 years ago, the chemistry, and information regarding optimising control of Knotweed was not available. Again, control is easily achieved, if undertaken correctly.

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Personally I would like to see the removal of rhododendrons.

Even after removal where they were is a toxic humus layer that lasts for years.

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7 minutes ago, P.K. said:

Personally I would like to see the removal of rhododendrons.

Even after removal where they were is a toxic humus layer that lasts for years.

Not all rhododendrons though, just those growing wild on the rock and in Wales (Rhododendron ponticum). Also Rhododendron ponticum attracts the bees away from other plants I think. Cornwall council paid a local large garden to remove these bad ones.

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