Growing Magnolias In Pots and Containers – The Complete Guide
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Magnolias are one of my favourite shrubs and I have several varieties in my own garden, from the smaller growing Stellata and Susan that flower in spring, to the summer flowering Magnolia Yellow River which is a really impressive tree. These small trees present abundant blossoms of various colours, from white to purple, to pink and even yellow.
Many people are usually surprised that Magnolias can grow in large pots because these plants possess a wide root system, but there are a few varieties that will thrive in pots. My favourite Magnolia for growing in pots is actually the Magnolia ‘Stellata’. This is one of the smaller growing varieties but it produces lots of star-shaped white flowers and there is even a Magnolia Stellata Rosea that produces white flowers tinged with pink.
It is possible to grow Magnolias in pots, as long as you follow the few guidelines that I will talk about in more detail below. Growing them in pots is a lot easier than you think. Let me start by looking at why Magnolias are suitable for growing in pots.
Why Magnolias are suitable for growing in pots
Magnolias can either be deciduous or evergreen, so consider which cultivar you want to grow. These plants are known to have extensive root coverage and even though the roots travel broadly, they don’t go too deep into the soil. This means that the containers do not have to be ridiculously large, although in general, the larger the better.
Another reason why Magnolias can be successfully grown in pots is down to their slow growth rate. These trees typically take more than a decade to fully mature; therefore, there is more than enough time to transplant them to the ground if need be. However, if you stick to the smaller varieties (such as the Stellata) they can stay in pots permanently with a little care.
Where to grow potted Magnolias
These plants enjoy plenty of sunshine; hence, place them in a well-ventilated and sunny spot. If you live in hotter and dry areas (as I know some of you might live in the US) place your Magnolia in an area offering partial shade. For those of you in the UK, an open sunny position should be fine, although you can still grow them in a semi-shaded position too. The shade will help the plant roots remain cool, save moisture and prevent wilting which can be an issue when growing them in pots if you don’t keep on top of the watering.
Choosing the correct compost
In terms of soil composition, Magnolias are not very fussy because they thrive in loam, sandy and clay soils. As long as the soil provides the correct drainage and it has enough nutrients, Magnolias will grow happily. In addition, it is important to note the soil’s pH to establish whether the plant will get the nutrients it needs to grow. Magnolias do well in alkaline to neutral soils but also even in slightly acidic soil. When growing them in pots I recommend using a John Innes potting compost with some grit mixed through to help with the drainage. The reason I recommend John Innes compost is because it is loam-based so retains more moisture than a standard multi-purpose compost does, plus it has long term fertiliser mixed in too.
If you do not want your Magnolia blooms to be damaged from strong winds, place them in a more sheltered position. Magnolia flowers are fairly delicate, especially the Stellata varieties so this helps the flowers last much longer.
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Planting Magnolias in pots
Before you choose which cultivar to grow, you have to consider the full height of the plant when it is mature, the colour of the blooms and if the Magnolia is deciduous or evergreen. The size of the matured shrub will affect the container size you will plant it in.
Choosing the right size container
Before selecting your container, ask yourself if you are growing the Magnolias permanently in the pot or just temporarily. If you are only growing the trees to transfer them to the ground at a later date, you don’t have to get a very big container, a little larger than its current size will be fine.
However, for those growing Magnolias in pots permanently (which I think most people reading this guide are) you must select a suitably sized pot because Magnolia roots spread wide. In general, the larger the pot the better, however, you also don’t want the plant to look ridiculous in an oversized pot. I recommend using pots twice as wide as the root ball and as deep as it is wide. I then like to pot them up every few years until it is in the largest pot I can get away with. This gives the tree ample space to grow for more than a decade without constricting the roots.
A well-sized container will keep the roots in place instead of them emerging through the drainage holes. If you see any roots poking out of holes in the container, it is time to transplant to a bigger pot or in the ground.
As with all pots, make sure there are holes in the bottom and cover them up with some crockery to avoid them getting blocked up. It is also worthing noting that it is best to use a heavy pot that will help keep them upright, so terracotta or stones pots often work the best.
Moving Magnolias from one pot to another can be a tricky affair if you don’t know what you are doing. Ideally, you need to take care not to damage the root ball as the roots are essential for the plant to re-establish itself and get a good start.
Once you find a suitable container it is time to transplant. It is good practice to stop watering the tree for about three days before moving into a different container. This is because wet soil is trickier to handle compared to compact soil around the root ball.
When planting, make sure that the top roots are just below the soil line, so basically they need to be planted to the same level as it was originally in the pot. Transplanting Magnolias too deep into the soil may cause the bark to deteriorate and be prone to diseases like canker.
It’s also worth noting that you can buy rooted balled magnolias between November and March and these are often cheaper. These are basically Magnolias that have been grown in the ground and dug up and the roots wrapped in sacking ready for planting.
Caring for Magnolias that are grown in pots
Young Magnolias need monitoring as they grow because it is easier for diseases and pests to attack. Once the tree establishes itself, there is not much work to do except for a little maintenance here and there. Some of the things you should consider doing for your Magnolia include:
Water your Magnolias frequently. These trees are partially drought resistant, but they need their daily dose of water during dry spells. This is especially essential for young trees or those planted in warmer areas. Watering daily does not mean you flood the container; the soil just needs little water to retain moisture. Just be careful not to overwater.
Magnolias don’t require feeding often. When the new growth appears, use your preferred fertiliser in measured quantities to avoid overfeeding the plants, a general fertiliser will be fine. Traces of salt damage or leaf edge burns usually identify overfed plants.
Mulching to help retain moisture and provide some winter protection for the roots
Mulching should not be overlooked because it helps the tree retain moisture and acts as a temperature regulator for the roots. Introduce fresh mulch occasionally but make sure the mulch does not touch the bark, this may mean removing the mulch from the previous season. This is because lack of ventilation encourages a breeding ground for diseases and pests.
To learn more about pests and diseases to watch out for on magnolias, read my guide here
Pruning helps maintain the tree’s shape and removes dead or whippy branches. Prune your evergreen Magnolias in the spring and deciduous varieties in the late summer. Pruning is usually minimal.
Magnolias grown in pots are more suspectable to frost damage. I recommend moving them to a shaded place for winter with a little shelter, perhaps against a wall. I also recommend wrapping the pot in bubble wrap or sacking to insulate the roots and little. You can also wrap the plant itself in fleece or buy a fleece jacket. When temperatures are better in the morning, remove the fleece to allow the plant to function normally.
If you have a cold greenhouse, you could just leave it in there for the winter, just don’t forget to check if it needs watering occasionally and give it some water if the soil is dry.
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