Mimosa is one of the most beautiful winter-flowering shrubs, renowned for its exceptional bright gold yellow flowering.
Key facts about mimosa
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
Proper planting of the winter mimosa tree, its pruning and the care you’ll give it will help you have a magnificent mimosa tree, whether in pots or in the ground in the garden.
- Read also: Albizia julibrissin, the Mimosa tree of the Americas
Planting a winter mimosa tree
Mimosa is planted preferably in spring or in fall in a sunny spot and, ideally, sheltered from wind.
If you choose to grow your mimosa tree in a pot for a deck, balcony or terrace, its fragrance will spread in the entire vicinity as soon as the first flowers unfurl.
Indeed, mimosa tree particularly loves sun-endowed emplacements that are protected from drafts, and especially well-drained soil.
- You’ll do well in avoiding heavy clay soil.
- For chalky soil, select a flowering mimosa tree that is grafted with a local native root stock. It will be better suited to that particular soil type.
- Follow our tips on how to plant a mimosa tree.
- Propagate your mimosa tree through cuttings in summer (highest success rate, but spring is also fine).
- Gather seeds from a tree, they germinate readily.
- You can even grow a new mimosa tree from bark.
In regions with harsh winters, your best option is to plant your mimosa tree in large pots so that you may bring them indoors over winter.
Growing mimosa in a pot
- Never use a pot that sits in a water retention device, the pot must drain freely at the bottom for the water to run off.
- Start with a smaller pot for it to develop its root system.
- Ensure it stays sheltered from wind.
- Mimosa requires sun to bloom.
After 3-4 years, the time has come to repot it in a larger pot.
Soil mix for growing mimosa in a pot
Use a well-draining potting blend:
- 10% river sand and for the rest, half-and-half flower potting mix and peat.
- Add a few handfuls of compost on top.
- If the pot is too large, topdress instead of repotting.
Pruning potted mimosa trees
Unlike a mimosa tree that is planted in the ground, which can be left to grow freely, a potted mimosa must be pruned.
- The pruning is performed after the blooming.
- Shorten all the branches, giving the tree the shape you desire for it: sphere, cone, etc…
Watering and fertilizer for potted mimosa trees
Mimosa shrubs grown in pots dry up much faster, and must thus be watered often.
- Water regularly but not too much, so as to not drown the roots while still maintaining constant moisture in the soil.
- Provide flower shrub fertilizer during the entire growth period.
- Or use natural fertilizer every two weeks during spring and summer for nutrients.
Mimosa tree and winter freezing
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.
Potted mimosa tree in Winter
A mimosa grown in pots isn’t as hardy to the cold and must be brought 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 the branches with the winterizing fabric at the onset of the first frost spells. Your mimosa tree will be effectively protected from freezing.
- Also protect the base with a thick layer of dried leaf mulch.
If you transfer a potted mimosa to the ground, remember to winterize it for at least three years. This is especially important if you’ve previously been bringing it indoors for protection. These first three “outdoor winters” will gradually harden the tree until it can cope against freezing on its own.
Pruning and caring for mimosa
Once properly settled in with a developed root system, the mimosa tree calls for minimal care. The only thing you might fear is having a late deep frost spell hit the mimosa tree in full bloom.
Otherwise, mimosa is so vigorous that some people call it an invasive plant. But stand assured: regular care and pruning will restrain its rapid growth.
How to trim a mimosa tree
Pruning of the mimosa tree takes place after the blooming because if you cut the tree in winter, you won’t have a single flower.
- Cut branches that have born flowers back lightly.
- As soon as they appear on the trunk, pinch suckers off. These usually shoot out at ground level, and they’ll weaken the rest of the tree.
If, at the end of winter, you notice branches that are broken and blackened because of freezing, feel free to cut them off because they, too, would weaken the tree.
How fast does a mimosa tree grow?
A single shoot can grow up to 5 feet (1.5 meters) in a single season!
- From this shoot, in the next season, more side branches will fan out.
If you want a low, bushy shrub:
- snip every branch as soon as it reaches two feet (50 cm).
- They will branch out and create a round, dense shrub that will be covered in flowers in winter.
- Don’t worry about the timing, this can be done any time.
- Also, feel free to cut back drastically if you need to reduce the size of the tree. Mimosa can cope with hard pruning quite well.
If you want a tall, tree-like shape:
- Let the topmost, leading stem grow freely.
- Cut out suckers that grow from the side of the trunk.
- Remove suckers up to the height you want your “trunk” to look like.
- Above this, branches will start fanning out and grow, forming a tree-like crown.
Mimosa will start back from the roots even if freezing killed the trunk off. Nurture the new sucker depending on how you wish to shape your tree.
Note: Always prune your tree just after a split or y-junction with a smaller branch. An alternative is to prune just after (above) a bud that can take the lead and grow. Otherwise you’ll end up hatracking your tree, which isn’t a good thing.
Watering a mimosa tree
Mimosa isn’t a tree that requires much watering, except when potted, of course. However, it hates excess moisture that has a tendency to make the roots rot, eventually killing the tree.
Watering a mimosa tree 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 mimosa tree’s needs.
Watering potted mimosa
- Mimosa trees grown in pots require regular watering that is moderate in quantity during winter. Only provide it when it isn’t freezing.
- In summer and in case of hot weather, water in the evening to avoid having water evaporate immediately.
Mimosa tree, key points to know
Its foliage is evergreen and its blooming has a fresh, appealing smell.
Winter’s deepest and darkest months is when this tree drapes itself in full color and releases its delicious spring-like fragrance throughout the neighborhood.
You can also take advantage of all this tree’s gifts on your terrace, balcony or deck if you plant it in a large garden box. Simply water it as soon as the soil turns dry.
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. In addition, for Americans, a mimosa is a tree of the Albizia genus, the silk tree.
- More clarity on the different acacia tree types
Now, about varieties: over 1200 mimosa tree species have been numbered throughout the world, and the first ones were introduced in Europe first along the Mediterranean, then along the Atlantic. They’ve spread across the temperate hemisphere ever since.
Smart tip about the mimosa tree
No need to add any fertilizer because a mimosa tree never needs fertilizer, even upon planting. An exception to this is when growing mimosa in pots: the soil must be replenished.
Simple mulch is enough and will keep water from evaporating and weeds from growing.
Your mimosa tree will happily stay small if you prune it often, and if you let it grow it can turn into a tall tree.
Winter mimosa on social media
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Credits for images shared to Nature & Garden (all edits by Gaspard Lorthiois):
Dreamy mimosa branch (also on social media) by Tomoko Uji under Unsplash license
Potted mimosa by Nacho under © CC BY 2.0
Mimosa snow by nofrills under © CC BY-NC 2.0
Tall blooming mimosa by Rosalyn & Gaspard Lorthiois, own work
Mimosa golden flower (on social media) by Nicola Giordano ★ under Pixabay license