Invasive oxalis

[johnralphcarpenter]

Can anyone put a name to this tiny invasive oxalis, which seeds itself in pots, cracks in paving, everywhere really. Flower is 7mm across, leaves 5mm.

[Maggi Young]

I think this persistent and colonising little hooligan is Oxalis corniculata. I believe the bronze leaved  similar plant is also that species.  Tracts of ground disappearing under it here - hard to dig it out from cyclamen and  other bulbs. 

[astragalus]

Returns here every summer no matter how many times I remove it.  I just try to remember "a weed is a good plant in the wrong place", but I don't truly believe it.

[Alan_b]

I have the bronze-leaved form.  It makes a very deep root which allows it to over-winter, it is drought-tolerant and the seeds are explosive.  But it seems to like full sun and has not spread to the shadier parts of my garden. 

[ChrisB]

Nightmare plant in my garden also.  No matter how many times I dig it out it comes back.  Must be loads of seed.  I'm also battling against tropeolum ciliatum that has some huge tubers now very deep down.  Another nightmare but this one I must confess to having introduced myself.

[Alan_b]

In favour of Oxalis Corniculata, it does not run produce runners that are hard to remove (spreading only chiefly by seed), it does not appear to inhibit the growth of surrounding plants and it is not wholly unattractive.  It just pops up where you do not want it.

[Anthony Darby]

So which similar species has runners which may or may not be just below the soil surface?

[Jupiter]

I thought that was O. corniculata? Spreading by runners just below the surface, which break easily when you're weeding it out guaranteeing that you always leave some behind no matter how careful you are! At least it doesn't form bulbs. I have another species with little pink flowers which does.

This weed is rife in the nursery industry which is how it came to my garden. It loves to form dense mats in the top of pots from which its seed are explosively broadcast far and wide. I've actually be pinged in the eye by seeds while pulling it out! The little purple form seems to do better in sunnier more exposed positions so I have it in my sunny beds in the front garden. I like to use a regular cutlery fork to weed these out.

 

[Alan_b]

I went outside to pull some up and yes, I was being over-optimistic, and there are runners.  But these tend to form shallow roots initially and the stems are strong so they are relatively easy to remove if you don't wait too long.  On the other hand, the main plant forms a deep somewhat tuberous root that is very much harder to excavate.

Jupiter mentioned using a cutlery fork and I was wondering if some strong nail scissors used to cut the stems before they flower would eventually allow the plant to be eradicated in areas where proximity to other plants precludes more drastic measures.. 

[Anthony Darby]

I first encountered it in our school greenhouse. Then plants in my classroom. Not only do the seeds ping, but they stick to things too. The window used to get covered with them. Explosive on contact and then spread further if the stick to a passing animal or wellie boot!

[Jupiter]

It's a clever little plant really isn't it? You have to give it that. Yes I've had them in glasshouses at my work and I also noticed that the seeds stuck to the walls! Nurserymen everywhere must hate this oxalis with a passion.

[johnralphcarpenter]

It's a clever little plant really isn't it? You have to give it that. Yes I've had them in glasshouses at my work and I also noticed that the seeds stuck to the walls! Nurserymen everywhere must hate this oxalis with a passion.

Clever,yes! I'm beginning to like it.

[ChrisB]

At the Plant Heritage sale in June Kirkley Hall, our host (an agricultural college), had hanging baskets of them and were trying to sell them. I was aghast...

[fermi de Sousa]

At the Plant Heritage sale in June Kirkley Hall, our host (an agricultural college), had hanging baskets of them and were trying to sell them. I was aghast...

Obviously  "if you can't beat'em, join'em" or try to sell'em!
cheers
fermi

[Jupiter]

Oh that's a great idea! Hang it up high so the seed can broadcast far and wide, all over the garden!!! .