Uh Oh - do I have Japanese Knotweed?

tombrown

Chatting to my brother in law last week about how he has an infestation of this stuff and has been trying for years to get rid of it (good news - he is gettign there ...). When he described it to me it sounded suspiciously like the plant I have growing around the pump house in my garden. It been there since I moved in to the house in 1999 and proves a very effective screen. I remove the dead stalks every February & it grows back in the spring. It really doesn't seem to be invasive . the odd stem appears in the lawn it is beside, but the mower deals with them, other than that it really hasn't spread in the last 18 years. It also does not seem to have the white flowers that are shown here - PICTURE , but otherwise it does suspiciously resemble other images.

I'll post a couple of photos in the next entry

Oldtree

looks more like a cornus

looksee

I am not sure what it is, but on balance I would say it is probably not. Knotweed has a zigzag stem, older stems seem to be reddish and the leaves are not as shiny as your plant. It is a bit difficult to see these from your photo. It used be possible to send samples to the National Botanic Gardens for identification of plants, but I am not sure it is still possible.

LurkerNo1

That is not JKW, you can relax

howdoyouknow

It's hard to tell from that photo. The leaves look like knotweed but appear smaller and darker green in you photo. Are the stems hollow and bamboo like with closed sections every 8 inches or so?

magicbastarder

were the photos taken with the leaves wet or dry?

tombrown

SO far I like LurkerNo1's answer the best, and am tempted to take that and stop asking ... but given the questions being asked I am not sure this is done & dusted.

Attached a few more photos from one I just cut down (one of the larger/older ones - about 8' tall), and some answers to the questions :-

- yesterday's photos were taken in the rain, which explains the shiny leaves. In the attached photos it is drier
- yes stems are hollow & close at each of the sections you can see in the photos (8-10")

tombrown

A couple of other points that may or may not be relevant

- the ground is very rocky, with only a few inches of soil before you hit limestone
- the plants grow around the pump house, beside a river. They have been there for > 18 years and there is no visible damage to the pump house structure
- for years I have always knocked down the dead stems every February (by swinging a metal rake through them) and dumped them in another part of the garden. There has never been any growth from that pile of discarded stems
- as mentioned above there are no flowers on them at the moment, no do I recall ever seeing a flower

Delphinium

Its not JKW but it is not cornus either. If it hasn't spread in all those years it is not a problem.

Day Lewin

To be honest, if it was Japanese Knotweed ever since 1999, it would be a young forest by now; the stuff grows tall, rampant, clumping, spreading, with white feathery flowers.
It is a complete pest, and if yours isn't, then it's not JKW :-)

solataire

it is Jkw. this company can help you with proper identification.. http://www.thejapaneseknotweedcompany.com/japanese-knotweed-identification-service/

Achasanai

solataire wrote: »

it is Jkw. this company can help you with proper identification.. http://www.thejapaneseknotweedcompany.com/japanese-knotweed-identification-service/

The leaves look much broader than any images I see on a Google search, and the stems don't have that zigzag pattern that is apparently an identifiable feature.

There is a large section of japanese knotweed near the back of where I live (on public property) and it really doesn't resemble it, but I'm no expert. Speaking of, does anyone know of who to contact if JK is on public property?

looksee

http://www.corkcoco.ie/co/pdf/786446050.pdf

Cork CoCo have a leaflet about getting rid of it, but there does not seem to be any specific obligation on county councils to deal with it. You could report it (and report it and report it) but I think it will not be dealt with until there is some sort of a crisis somewhere. If the County Council deals with it by cutting it down or removing it in any sort of inexpert way then you could have a problem.

renandstimpy

Local council sprayed jkw on outskirts of our town last April .. may .. and had a sign up not to cut and all info on it .. it's dead now don't know what they used though

Achasanai

looksee wrote: »

http://www.corkcoco.ie/co/pdf/786446050.pdf

Cork CoCo have a leaflet about getting rid of it, but there does not seem to be any specific obligation on county councils to deal with it. You could report it (and report it and report it) but I think it will not be dealt with until there is some sort of a crisis somewhere. If the County Council deals with it by cutting it down or removing it in any sort of inexpert way then you could have a problem.

I've seen signs elsewhere (as Renandstimpy mentioned) but I guess it just depends on the council in question. Pretty worrying as I can see the examples that I've seen becoming a problem for some of the houses in a few years.

tombrown

Bumping this thread to give an update

While I loved the majority opinion that this was not JKW, I did contact these guys - JKW Company - as advised and sent them photos. I just got a phone call from a very polite gentleman who told me that it is indeed JKW and, despite the fact it has been there for 17+ years with no obvious ill effect or spreading, it is probably aggressively spreading underground.

He went on to explain they would happily offer a comprehensive survey to assess the spread & threat & recommend a course of action. Of course the survey is not free, and will set me back 240 euro :O

This has now frightened me - while I dont want to doubt his expertise, I would really like to get a definitive identification from someone who doesn't stand to profit from it being positive, before I take next steps.

Does anyone know if there is some form of independent body that could help?

I would stress that I am not trying to cast negative aspersions on the quality of the service the company above offers, I just want a bit more peace of mind before I make a significant investment.

lottpaul

Saw a Tidy Towns item on RTE Nationwide last night where it was stressed that knotweed should never be cut etc and should be treated in the autumn (good advice) and to contact the local council who would/might (?) get rid of it for you. Am not sure if that's true for every council and on private land - the patch in question was on the roadside but might be worth giving them a call before you spend €240 .....
Even if they don't I think you'd buy a lot of weedkiller, sprayers etc etc for that amount of money and do the job yourself too. The trick is to treat at the right time of the year -- and to persevere.

amber2

tombrown wrote: »

Bumping this thread to give an update

While I loved the majority opinion that this was not JKW, I did contact these guys - JKW Company - as advised and sent them photos. I just got a phone call from a very polite gentleman who told me that it is indeed JKW and, despite the fact it has been there for 17+ years with no obvious ill effect or spreading, it is probably aggressively spreading underground.

He went on to explain they would happily offer a comprehensive survey to assess the spread & threat & recommend a course of action. Of course the survey is not free, and will set me back 240 euro :O

This has now frightened me - while I dont want to doubt his expertise, I would really like to get a definitive identification from someone who doesn't stand to profit from it being positive, before I take next steps.

Does anyone know if there is some form of independent body that could help?

I would stress that I am not trying to cast negative aspersions on the quality of the service the company above offers, I just want a bit more peace of mind before I make a significant investment.

Relative has JKW it's only there a few years perhaps 2 to 3 years at most, it is very tall and spread quickly, they went to the agri section of Our local Dairygold Co Op, staff there identified & help treat it with suitable weed killer, may be worth a call if your anywhere an Agri store, not too sure what part of the country your in.

tombrown

I'm in Clare - thanks for the advice

Achasanai

Have you tried comparing it to some of the identification pages on the net? Here's one another poster recommended on a different thread:

http://www.fisheriesireland.ie/invasive-species-1/242-japanese-knotweed-id-sheet-1/file

If the company are hoping to get 240 euro from you, they are going to suggest that it's JK. Not that it isn't, but y'know.

I get that there are similarities but it didn't look from your photos that the plant has that zig-zag pattern. Another thing is that they should be flowering at the moment. Have you seen it flowering and can you describe it?

looksee

Are the stems hollow. Are they in sections like bamboo. Are they zigzag. Do they have reddish markings on them. The leaves have a reddish stalk that extends into the leaf. There are numerous plants in the knotweed family and some of them are very similar. Russian Vine is one that can be a bit of a nuisance if it really gets going, but it is not a danger to buildings.

There is a limited plant and fungi identification service provided for specimens sent by post to the herbarium (Herbarium, National Botanic Gardens, Glasnevin, Dublin 9). Plants or fungi brought in for identification should be left at the Visitor Centre and collected later if required. Old varieties of Apples, Roses and Daffodils, as well as a number of other cultivated plants can be very difficult, if not impossible to identify.

I suggest you put a spray of leaves and stalk into a ziplock plastic bag and send it with a SAE to the Botanic Gardens.