delicate yellow mimosa flowers

It’s mid-February and the mimosa trees are about to blossom, signalling the start of Portuguese spring in my eyes. Pretty soon, the hills around me will be covered with bright yellow splodges, as though someone has dipped a sponge in yellow paint and dabbed the landscape. Already, the mimosa trees seem to be covered in a furry yellow mould as the buds begin to open.

In another week, clouds of tiny yellow puff-ball flowers will dominate the silver-green feathery leaves underneath them. My drive into Coimbra will be studded with lemon-coloured trees. One of my walking routes will take me through a golden arch formed from the mimosas that grow either side of the track.

Mimosa as an invasive species

I’d never heard of or seen mimosa, aka Acacia dealbata, before I came to live in Portugal. Now that I’m here, there’s no escaping it. Much as I love the delicate, unusual flowers, I can see why this species has become a serious problem in this country.

Mimosa was first introduced to Portugal from Australia over a hundred years ago precisely because it’s so pretty. Before people realised the damage it could do, it was even cultivated and used to help prevent soil erosion.

It readily adapted to conditions in Portugal and grows extremely quickly, producing lots of seeds. The trouble is, Mimosa grows so well that it’s taken over and destroyed a lot of the natural plant life.

It’s also a bugger to get rid of once it’s established. If you don’t destroy all of the roots, you’ll just make the problem worse as new shoots will sprout up all over the place.

mimosa on the river Alva

Mimosa is probably the most aggressive invasive species of tree in Portugal. It’s become such a problem that it’s now against the law to cultivate it, sell it, or keep it for ornamental purposes. So bang goes my idea of digging some young plants up and growing them in pots in the garden.

In some areas of the country, groups of school children and volunteers go out into the forests to pull up the saplings by the roots to try and prevent the mimosa population from getting any bigger.

Mimosa, however, isn’t giving up the fight easily.

Mimosa, a super self-propogator

Once the yellow flowers have come and gone, they are replaced by thousands of seed pods which dangle from the branches. These pods mature from pea green to a rusty brown then fall to the ground, creating a crinkly copper carpet.

Each pod contains about eight tiny black seeds so it’s no wonder that each year, new seedlings appear and take over disused forest tracks or fill any gaps between existing trees.

Mimosa buds, leaves and seed pods below
Mimosa buds, leaves and seed pods below

So it looks as though the start of spring in Portugal will continue to be heralded by sprays of yellow for many years to come. If you want to see this for yourself, you need to be in Portugal around February to mid-March.

This post forms part of my Personal A to Z of Portugal.


  1. it is invasive but pulling young saplings up by the roots is more effective than chopping the trees in order to eradicate them…do it for 2-3 years and you can see the difference as the native trees spring up..

    1. Absolutely, but it’s a seemingly endless task, or at least where I live, and there’s no one to do it.

  2. Very late for a comment I know, but I have been told by a Portuguese chum that the best way to kill Mimosa is to ‘ring’ the bark, remove 10-15cm all the way round somewhere near the base. Apparently if the tree is just chopped down it will throw out a bunch of new shoots.

    1. Author

      I don’t know whether or not that would kill it. Probably. The new shoots problem is true, I’m sure.

  3. This is another big ecological problem here in Portugal. The govermente is trying to iradicate them from our natural parks but has been very dificult, each year they grow stronger, specialy after a fire!

  4. thank you, Julie, for M = Mimosa –
    the word is a metaphor in German language
    for being quickly depressive …

    1. Author

      Oh dear! At least the flowers are pretty and would hopefully cheer people up 🙂

  5. I never realised you had Australian plants doing damage over there. I can imagine this plan would thrive in the conditions. Most of our native plants have a strong survival technique (floods, fires, drought) and when not faced with those challenges, off they go!

  6. We recently removed a couple of Mimosas from our garden. I did not realise the problems with the roots! We just chopped them down and poured acid on the stumps.

    1. Author

      Hopefully, the acid will have got into the root system and destroyed it. But if you start seeing new shoots, it didn’t work. Fingers crossed that you managed it.

  7. The Mimosa is so pretty, what a shame it’s so invasive. Excellent post Jo!

  8. Wow! This stuff is pretty but dangerous! It is included in the World Conservation Unit top 100 list of invasive species. It’s a bit like Japanese Knotweed in the UK. Seems that the best advice is definately do not plant it up in your front garden!

    Now that you have confused us by jumping to M where will you go next?

    1. Author

      Not sure which letter to go to yet. I think I’ll keep you guessing, too!

  9. Now you’re being sneaky, jumping to M! No, I appreciate that the mimosa would otherwise be gone when you progressed to M. I’m expecting it to be in full bloom in the Algarve.

    Didn’t realise it was so invasive- what a shame. Another of my favourites, the Hottentot Fig that you find on the island beaches is too. Still love it.

    1. Author

      Sorry, Jo. Couldn’t hold back on M so thought I’d mix things up a bit.

Over to you. Please share your thoughts in a comment.