Acacia dealbata, commonly known under the name winter mimosa tree, decorates our gardens with superb golden yellow blooms from January to March, depending on the climate.
Key Acacia dealbata facts
Name – Acacia dealbata
Family – Mimosaceae
Type – tree
Height – 13 to 32 feet (4 to 10 meters)
Exposure – full sun
Soil – well drained and sandy
Foliage – evergreen
Flowering – January to March
Planting Acacia dealbata
Plant this indifferently in spring or fall in a sunny spot and, ideally, sheltered from wind. Note also that Acacia dealbata tolerates slightly windy spots.
The acacia dealbata tree thus likes rather sun-endowed emplacements and especially well-drained soil.
- Acacia dealbata is especially suited to the Mediterranean area and along the Atlantic coastline.
- You’ll have to avoid heavy clay soil.
- In chalky soil, select a grafted tree for which the root stock will be better suited to that particular soil type. Acacia retinodes (also called swamp wattle) is a great choice for the root stock.
- Follow our guidance on how to plant your Acacia dealbata shrub.
- Propagate your A. dealbata tree through cuttings in summer.
If you choose to grow your acacia dealbata in a pot for a deck, balcony or terrace, its fragrance will spread in the entire vicinity as soon as the first flowers open.
Actually, in regions with harsh winters, it’s better to plant Acacia dealbata in pots or large containers so that you may bring the shrub indoors over winter.
Acacia dealbata in winter
The Acacia dealbata tree can resist freezing, if moderate. 23°F (-5°C) is the coldest temperature it can survive, especially when bouts of freezing only last a short while.
A potted mimosa tree isn’t as hardy to the cold, so bring it indoors for shelter in a cool spot over the winter if it freezes in your area.
- You can also put horticultural fleece to good use, wrapping it around the branches at the onset of the first frost spells. This will be very effective in protecting the mimosa tree from freezing.
- Also protect the base with a good layer of dried leaf mulch.
When growing directly in the ground and if the weather freezes deeply in your area, protect your tree by implementing our advice on protecting plants against the cold.
Pruning and caring for Acacia dealbata
Pruning of your A. dealbata takes place after the blooming because if you cut the tree in winter, you won’t have a single flower.
- Lightly cut back branches that have born flowers.
- As soon as they appear, pinch off suckers that shoot out at ground level, because these will weaken the rest of the tree.
- If your Acacia dealbata is grafted, remove any suckers that emerge from the root stock.
If, at the end of winter, you notice broken and blackened branches because of freezing, feel free to cut them off because they, too, would weaken the tree.
Watering acacia dealbata
Acacia dealbata isn’t a tree that requires much watering, except if potted.
It hates excess moisture which has a tendency to rot roots, eventually killing the tree.
Watering acacia dealbata planted in the ground
You must water in case of prolonged dry spells, but otherwise stocks of water contained in the tree itself should answer the acacia dealbata tree’s needs.
Watering acacia dealbata planted in pots
Mimosa trees grown in pots demand regular watering which should be moderate in quantity over winter and provided only when it isn’t freezing.
In summer, and in case of hot weather, water in the evening to avoid having the water evaporate immediately.
Diseases, pests & problems with Acacia dealbata
A very vigorous tree, Acacia dealbata is only rarely subject to disease.
Acacia dealbata dripping sticky sap from bark
After a heat wave, if it rains or too much water is provided, sometimes the tree builds up excess pressure in its trunk and stems. Too much sap and water swell up from the root system.
To avoid bursting entirely, special cells along the trunk wall break open and release extra pressure. These act like natural valves or nozzles that ooze out a sticky, sappy substance. This is called gummosis.
It’s a healthy sign when it only occurs occasionally. If it repeats often, perhaps the growing conditions of the tree should be looked at.
- Although this substance is mostly water, you should rinse it off with a hose. If not, you’ll risk stains on your car, concrete driveway, or pavement.
In a way, this is a similar process to that of guttation, where plants start weeping tears from leaves.
All there is to know about the acacia dealbata
Acacia dealbata is famous for its superb golden yellow blooming that decorates gardens and decks at the heart of winter or at the beginning of spring.
Its foliage is evergreen and its blooming has a fresh, appealing smell.
The middle of winter is when this tree drapes itself in full color, and releases its distinctive odor throughout the neighborhood.
You can highlight Acacia dealbata’s perks on your terrace or deck if you plant it in a large garden box and water it as soon as the soil turns dry.
Acacia dealbata was introduced in Southern France in 1820 and over 1200 mimosa tree species have been numbered throughout the world.
Note that there is a certain confusion in terms: the tree that is commonly called Mimosa tree is actually an Acacia, whereas the tree that is commonly called acacia is really the locust tree.
Smart tip about acacia dealbata
No need to add any fertilizer because acacia dealbata (mimosa tree) doesn’t need fertilizer, even upon planting.
Simple mulch is enough and will keep water from evaporating and weeds from growing.
Acacia dealbata on social media
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Credits for images shared to Nature & Garden (all edits by Gaspard Lorthiois):
Blooming Acacia dealbata (also on social media) by Dan under Pixabay license
Cluster of flowers (also on social media) by Alessandro Ruggeri under Pixabay license
Thanks for the useful info. I have a large acacia dealbata tree that is at least 12 years old (maybe older). It’s produced some suckers from its roots, which I now realise need to be removed for the health of the tree. Can I replant and grow these suckers, to create new trees?
Yes of course, Sarah! They’ll root very quickly, like cuttings. Remember to remove about half the leafage so it won’t be too much of a drain on the budding roots. You probably already saw that this Acacia will root from nearly anything.
This is fantastic – thank you so much, Gaspard!!
Hi Gaspard – thanks so much for responding. This is really good to know… we’ve got 2 large suckers, so we’re excited that we can potentially get 2 new trees from them!
The suckers are coming up from the roots of the tree, rather than growing out of the bark… will we damage the main tree if we dig up the suckers (which will obviously involve some damage to the roots of the main tree)? We’re hoping the main tree will live for another few years, so we’re a bit worried about damaging its roots.
Hi Sarah, of course the main tree will get some damage, but nothing it shouldn’t be able to cope with. As long as you try to make clean cuts, it should be ok. Usually such trees have a half-dozen main roots or more, and you’ll be taking out only two of them so it’s ok.
Hi, I recently planted some acacia dealbata seeds and only one sprouted, but the leaves are yellow— I keep it inside in pretty direct light and water it 2x a week. Am I missing something?
Hi Jess, from what you’re saying it doesn’t sound like you’re missing anything, but the plant seems to think otherwise, and somehow its opinion counts more than ours in this case…
It might be damping off. When you water, if excess water has no place to go it’ll start rotting the plant out from the bottom.
I have used merox 5 G for my mimosa dealbate tree which has practically killed it. What do I need to do now?
Thanks,
Hi. It isn’t very easy to save a “poisoned” tree, but here are a few things you can try. You can find them in this post on how to save a tree sprayed with too many chemicals.
Thank you but the sap was on the cement, we had rain, it all washed away from two trees, different locations. A third tree has a bench underneath, and that sap washed away as well. I am wondering if it is sap or something else from these trees.
Well that’s great news! I guess that sap really was mostly excess water. Good thing to know that should rain not be timely, a simple hosedown will do the trick. All the best then, Elizabeth!
I live in San Diego, planted eight of these trees five years ago from one gallon pots. They are twenty feet tall now, are beautiful but are dropping sappy stuff on my concrete driveway. Why is this and how do I wash off my driveway?
The sap is clear and shiney. One of the trees is about 8 feet from a bay window, in a walking garden that gets water once a week. Is this a concern?
Ok, shiny clear sap shows that’s just what it is and not an infection of any sort.
Regular watering or not watering anymore won’t change much regarding the sap issue. I think you’ll find it’s a seasonal problem with more sap in autumn than in the other months.
Depending on what the setup is, if the sap is really an issue you might want to keep the tree from branching out above the driveway too much with regular pruning.
As for the size of the tree near the house, it’s best to take a minute and think about how the tree will grow. Perhaps it might be an option to prune the tree to keep it small, but you can also wait until it gets too large for comfort. If your area is prone to strong winds, consider that branches might come hit the window and break the glass if too close. Hope this helps!
Hello Elizabeth! Mimosa trees have a powerful root system – that’s why they’re such vigorous trees. At times, the roots take so much water in that the tree can’t hold the pressure. Tiny cracks in the bark where tree branches join together are the natural way for sap to bleed off. It drips to the ground.
Usually the easy way to clean it is using rubbing alcohol on a wad of cotton or a rag, since sap dissolves in alcohol like wax. On large surfaces, which I expect since you’ve got those eight wonderful trees, go with either of the following:
– boiling water. Heat the kettle and dribble the water on and around the stains. That’ll make for quite a few back-and-forth’s to the kitchen, so borrow a neighbor’s kettle and pull out the extension wire so you have one cooking and one for cleaning. Take care to follow the runoff up until the side of the driveway as it might “settle” in river-like patterns if you don’t.
– powerwashing. If the sap isn’t too old, a powerwasher might do the trick in a jiffy. Check on natural detergents or environment-friendly concentrates designed for powerwashing driveways, they include special oil and wax components.
– ask your local mechanic what he or she uses to clean their workspace floors from all those grease stains.
Once you’ve found which solution works best for you, make it a regular part of garden maintenance: the older the stain, the harder the clean!
There isn’t much that can be done against the trees leeching sap, though, it’s really a natural response to the overload of rain they get in October/November while the weather is still clement after the dry San Diego summer months.