ID this Weed

[Huw.S]

Hi all,

My questions are, what is this weed called? And more importantly what is its weakness?!

It has appeared in one of my growing areas where I have a lot of stock trees close together in black plastic pots. It multiplies and spreads incredibly fast and (dare I say it) seems to be resistant to broad spectrum herbicides. I have so far been pulling it out by the handful, but it is only to be replaced by hundreds of tiny seedlings, it germinates/ multiples on any surface (be that concrete, soil, wooden fence etc). I also have a feeling that the recent rain isn't helping my efforts.

I have attached a few photos showing a range of development stages, including one of the soil covered with hundreds of newly germinated ones (a week or so after removing the adult versions).

Any help would be greatly appreciated.

Huw

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[Keep Calm and Ramify]

I had some of this showing up last year in one of my comp tree posts and the wonderful Mel Brackstone advised me it was called military fern, or artillery fern = Pilea Microphylla. Luckily I could remove mine by hand before it spread too much. Looks like you've got base camp set up at your place.

[Huw.S]

Ok thanks! The name was enough for me to at least do a little reading on it, seems like glyphosphate with a brush (as tedious as that will be) might be the best approach. I also think some hot and dry weather would help, don't like my chances for that!

Any other tips would be appreciated!

[shibui]

Photos are not clear enough to be definitive for my old eyes.
This could also be a species of euphorbia That has become a common pot weed in recent years. Sets seed very quick after emerging, spreads seed over a distance and can be quite hard to spot when small. Looks like some of these may have had a recent name change to Chamaesyce.
spotted spurge -Chamaesyce maculata is one of a few closely related species - spotted spurgeChamaesyce maculata

Manual removal before seed is ripe is effective.
Brushing with glyphoste also works well if the infestation is bad.

Unfortunately there will still be more seed in the pots which will continue to germinate for a number of years. Continued vigilance is necessary no matter what control method you choose.

[Huw.S]

Photos are not clear enough to be definitive for my old eyes.
This could also be a species of euphorbia That has become a common pot weed in recent years. Sets seed very quick after emerging, spreads seed over a distance and can be quite hard to spot when small. Looks like some of these may have had a recent name change to Chamaesyce.
spotted spurge -Chamaesyce maculata is one of a few closely related species - spotted spurgeChamaesyce maculata

Manual removal before seed is ripe is effective.
Brushing with glyphoste also works well if the infestation is bad.

Unfortunately there will still be more seed in the pots which will continue to germinate for a number of years. Continued vigilance is necessary no matter what control method you choose.

Thanks Shibui,

I do know the spotted spurge and related species you're talking about and it isn't that. It is most definitely Pilea microphylla or Military fern after doing some research.

Have you or any others on here had any ill effects on trees by brushing weeds with glyphosphate? Are there risks of it leeching into soil and killing the tree for example?

[Raging Bull]

Hi Huw, I have this pesky weed come up all over my garden and in my pots as well . I've given up trying to eradicate it and just try to control it in my pots by hand weeding where-ever I see it. Where it comes up between the paving bricks and among the wood chip mulch I spray with Roundup glyphosate weed spray . It's an ongoing process as it grows so fast and seems to put seed out from very early in its life cycle and somehow even gets into pots on the highest shelves. If you find a better way of getting rid of it please let us know.
Cheers, Frank.

[shibui]

I use glyphosate regularly on pots to control a range of weeds - copper oxalis, couch, spurge, bitter cress, etc. I have never seen a problem resulting from using it. I use glyphosate in 2 ways - diluted 1:1 with water then brushed on to the weeds is the preferred way but I also keep a small spray bottle (the kind used for household cleaning products) with a more dilute mix so I can spray onto occasional weeds.
Glyphosate is only taken in to plants through leaves or direct into the sap stream through cuts. It does not affect roots so applying to the soil will not affect nearby trees. Be careful it does not get onto leaves of plants you want, especially when spraying nearby. Accidental application to a good plant can be washed off the leaves with lots of water or I have also just pruned off any affected shoots. Both need to be done within a few minutes to make sure the leaves do not absorb the chemical into the plant.

One of our local members also discovered that spray on insect repellent kills weeds. Aerogard was initially recommended but I tried a few others and they all seem to kill weeds despite having different active ingredients. I am not sure how these actually kill weeds but it is very quick and the weeds shrivel and die in a few hours. I have only used these a few times but have not seen any affect on the trees in the pots treated so far.

[Huw.S]

Thanks Shibui and Frank,

I will start trialing some things and will post on here any interesting results I find. The insect repellent is a very strange one but will definitely give it a go.