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Pseuderanthemum variabile 'Love Flower' 'Pastel Flower' What a pest of a weed in orchid collections.!!

Pseuderanthemum variabile 'Love Flower' 'Pastel Flower' What a pest of a weed!! 


This quite pretty Australian native Gesneriad (Africa Violet Relative) is a lovely plant in the wild.

From as far south as Bega  in Southern NSW all the way to New Guinea it is a relatively common butterfly attracting wildflower. It's issue is that it is also a bloody awful orchid weed, infesting pots, regardless of the media in that pot. 

It enjoys dark,moist rainforest areas and will grow in all soils and rock/gravel scree.

It has large seed capsules that develop on very young plants,so disperses easily from seed.

Its most irritating feature is its large rhyzome root system that makes it unable to be hand pulled.

The photo above shows the fat tuberous like carrot root.  When hand pulled, this breaks and even the smallest piece grows back into a full plant in no time at all!

It seems every time we buy an Australian Dendrobium orchid from further north than the border  (Vic /NSW) that this weed is in the pots.


We in the orchid trade are very very lucky that Linuron Weedkiller can be used over orchids with little to no effect on the orchids,but kill most weeds.

The frustrating thing is that Saintpaulia weed seems to be resistant to Linuron and is not killed by it.

When sprayed ,this plant just looks a little sad, turns purple for a month or two then powers away in full growth again. So basically ,its the only weed we cant control easily.

So how do we? We try to manually remove all of it at repot time .

Then comes the hard yard. 

Using a childs paint brush, we paint 50/50 Glyphosate/water on to the weeds leaves.

Water well the day before and then dont water again for as long as possible. Be careful, as Glyphosate or Roundup as it is also known is very toxic to orchids.

It doest though, take a LOT of glyphosate to kill an orchid, so dont be too scared to try it!



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  • Mary Tang on

    I have watched out for it since I first read this post and am happy to report that I found one; pulled it out roots and all and repotted it (the ‘weed’ that is). Thank you.

  • Nick Lloyd on

    It’s not a gesneriad! It is in the acanthus family, Acanthaceae.

  • Florian Wolf on

    We have Pseuderanthemum variabile (this is the name of the plant) now & then coming up in our seedling pots in the garden. It is quite lovely, so I try to gently removr it and plant it into a shady part of the garden, where it rambles through the leaf compost. The flowers at close up are very pretty, it comes in white and shades of pink to purple / violet, and it has a lovely scent. Also named ‘love flower’ it is one of the prettiest nuissances to have in the garden and greenhouse.

  • wes on

    I have had thin weed in my orchid collection since 1990. I have also passed it along to most members of our orchid society. I sure hope it works. Thanks for the information.

  • Debbie on

    Need to purchase these plants if you could please tell me where I can buy them from

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