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Growing magnolias in pots – the beginner’s guide
Last Updated on January 21, 2020 by John
Magnolias can be found in evergreen or deciduous varieties. The deciduous varieties which lose their leaves come winter are much more common in gardens across the UK and they are usually for sale at all good garden centres and nurseries. The main reason for this is that they produce stunning large flowers in spite of having few leaves which makes for an incredibly striking visual at the end of winter and beginning of springtime when not much else is flowering just yet, with stunning flowers juxtaposed by a bright blue sky, snow on the ground in some cases, and bare branches.
Magnolias may or may not be the best option for your garden depending on the type of soil and sun exposure you have. So before you head out to buy your next Magnolia and start planting, check to see whether your garden is a good fit, in most cases the answer will be yes as you don’t have to worry about soil quality and ph if you are planting one in a large pot or container.
A few tips to get you started when growing magnolias
- Magnolias prefer full sun all year round but they can survive if you have an area of your garden with light shade for just part of the day. If you only have low light conditions in your garden, you can theoretically grow Magnolias but they won’t produce many flowers. With pots, you can grow magnolias anywhere in your garden with adequate exposure.
- There are certain varieties that are better suited for container growing so if you plan on growing Magnolias in a container, be sure you’ve selected the appropriate variety.
- Different varieties reach various heights and spreads, sum spanning an average of 2.5 meters in height with a similar spread while others can reach up to 20 meters in height and spread. To that end, you want to be sure that you have enough space to allow a fully mature Magnolia to thrive wherever you plan to grow it. If for example you have a smaller space in your garden just make sure that you pick the right variety. The good news is container-grown magnolias will be somewhat restricted and will not get anywhere near the size they would in the ground, it’s just better to choose a variety that doesn’t grow to large in the first place.
- Certain Magnolia varieties grow best in slightly acidic or neutral soil but most do not thrive in highly alkaline soil so by growing in a container, you can amend the soil easily to suit the variety you have selected. In most cases, John Innes potting compost with some grit mixed through will be fine.
- Magnolia plants have shallow roots and because of that, you have to take precautions to prevent the soil from drying out. This is particularly problematic when growing in pots, as compost in pots dries out much faster than in the ground. You can help prevent water loss by adding mulch annually and water regularly when needed.
- Aside from the annual mulch requirement, most Magnolias will tolerate neglect once they get established because they have very low nutrient requirements thereafter and very minimal pruning requirements.
- Magnolias will all produce flowers spanning the end of March through the end of May depending on your local weather.
- You don’t want to plant them in an area that is subject to a lot of waterlogging. With pots, you can always drill extra drainage holes and add perlite to the mixture to help with this.
- Most Magnolias won’t suffer from pest or disease.
- It is recommended that you plant them in a slightly protected area so that they are not exposed to direct wind and so are positioned in a sheltered position. Severe wind exposure can damage the branches but it can also exacerbate the negative impact of frost.
Once you have verified that you are well-equipped to plant a magnolia, it’s time to get down to business.
Picking the right container for your magnolia
Pick a large heavy wide pot
When growing Magnolia’s you want to pick the right container to start. Stone or terracotta pots are the best for multiple reasons. First and foremost, a magnolia is quite large and therefore quite heavy. The weight of a stone or terracotta pot is significantly higher compared to plastic which will help support the weight of the Magnolia and prevent it from being blown over in the wind.
It is best to pick containers that have a base just as wide as it is tall. This will give it more stability and help it to maintain an upright position. You don’t want round pots where the top is narrower compared to the middle of the base because if you have to repot your Magnolia for any reason down the line, you might be able to get it out without breaking your container, plus they tend to be less stable.
Wood containers are very attractive and can be of course decorated how you see fit, but the problem is that Magnolias will be around for quite some time, not just one season and to that end, you will likely have to apply some treatment to the wood containers to help prevent decay as your Magnolia gets older.
Ensure you have adequate drainage holes to avoid waterlogging
Whatever the material you select make sure that it has adequate drainage holes. If it doesn’t, you can always drill more before you plant your Magnolia.
Choosing the right pot size
The size you select should be appropriate for the size of the Magnolia you have and its current pot size. Look at the container size in relationship to the size of the pot as a good starting point. For example, if you have a magnolia that is in a 5-litre pot, you might want to consider a 10-15 litre pot so that it has plenty of space to grow of the next couple of years, its best to pot up gradually than plant it straight into a very large pot straight away, this actually goes for most plants not just magnolias.
Planting a magnolia in a container
If you are going to grow in containers, it is recommended that you pick one of the Magnolia stellata varieties as pictured above, they are easy to identify from the star-shaped flowers in either white or sometimes tinted pink. These are comparably smaller and will do just fine with the restriction of a container.
When to plant magnolias in pots
When you purchase your Magnolia in a pot, it might have to be replanted immediately in a new container. If this is the case, you should replant it at the beginning of Spring but they will do well if planted in summer. You can get root balled magnolias which are usually more affordable and often large established shrubs, these can be planted between November and March when they are dormant and have no foliage but often already have flower buds on. Once you plant your Magnolia you should not have to replant it for several years, not until it outgrows the existing container.
Always clean old pots before using them again
If you are using a container you have ever used previously, make sure you clean it out, allow it to soak in a mixture of bleach and water to ensure it is sterilized before you plant your Magnolia. The last thing you want is for the residue of a fungus, or the unexpected pest problem to infiltrate your Magnolia immediately.
Choosing the right compost
Magnolias prefer slightly acidic soil, so you should choose a compost that is good for ericaceous plants like rhododendrons or azaleas. You can also pick an ericaceous mixture that is loam based with extra acidity which means going for a John Innes ericaceous compost. They will also grow in normal compost too if needed but a soil-based compost is always better to help retain moisture and the added weight helps prevent them from getting blown over.
Don’t forget to add stone or crockery to the bottom of the pot
You can help guarantee better drainage by adding stone/gravel or broken pieces of crockery from broken pots to the base of your Magnolia container. This will help prevent the holes from getting blocked up.
Planting your magnolias into its new pot
When you are ready, remove your Magnolia from an old container being careful not to damage the root ball. Be careful when you do this, the roots can break easily and any unnecessary pressure will break them. Place your new compost mixture into the container and transfer your Magnolia, backfilling once the magnolia is buried to the same depth that was originally. When you are adding the compost, you want to make sure the main stem is at the same level it was, and you can guarantee this by adding a few centimetres at a time and then lightly packing it down, never firmly packing it down, those roots need to be able to expand into the new compost as it grows.
When you are done, water it well to allow the Magnolia an opportunity to settle in place.
When you grow Magnolias in containers they require minimal care. The first thing you need to do is give them a regular supply of water but never over water. If you have two or three days of sunny weather and you forget to water them it can cause some damage so always be on the lookout for dry soil. If you are going on a holiday make sure to ask someone to come by and water your Magnolias. If that’s not possible, simply move them into the shade, in a cooler area while you are gone and think about adding a water time to an outside tap if possible.
Protecting contain grown magnolias in winter
Winter care for container-grown Magnolias consists of two key principles. The first is to prevent your soil from becoming waterlogged by reducing the amount of rain to which it is exposed. The second is to protect the soil from freezing conditions over a long amount of time as the root system can be damaged by regular exposure to frost.
Place magnolias in a greenhouse over winter if possible
If the winter in your area is particularly harsh and you suffer from heavy frost, cold weather, with high wind, it is recommended that you move your Magnolias into a greenhouse or in your garage from the middle of December until the start of spring, putting them outdoors during mild weather. You can help the springtime recuperation by adding a general-purpose fertilizer at the beginning of spring every two weeks in preparation for moving them back outside.
Wrap pots in bubble wrap and protect with fleece in freezing weather
If you don’t have a garage or a greenhouse where you can store the Magnolia, do not bring it inside. Other plants you can bring indoors for the winter but not a magnolia. The air inside your home will be too dry and too warm. The best solution here, if you have no other option, is to find the most protected area against the walls of your home and add some adition protection by wrapping the pot in bubble wrap and the plant in fleece. The physical walls of your home will be relatively warmer in the winter compared to the outside are so if you have no other options, this will protect them against the worst of winter with the help of the bubble wrap and fleece.
If possible find a position in your garden that protects the Magnolias from wind and from heavy rainfall. Too much rain on the soil in your container can cause root rot.
Only prune magnolias if you have to
If you see any wispy shoots that are detracting from the overall structure of your Magnolia plant, you can prune them. However, regular pruning will reduce the flowering for the next few years. As a general rule, it is not recommended that you prune Magnolias if you can avoid it. The only reason you should prune is if they are outgrowing the existing space. If you absolutely must prune your magnolias hard, spread it out over two or three years. Remove diseased branches first and then branches that cross one another. The idea is to keep the middle of your Magnolia tree open by pruning the branches back to the main stem. Do it in the middle of summer after flowering. If you do it any other time of the year it will cause the cuts to bleed which makes your plants susceptible to infection.
Pests and Diseases
Slings and snails
If you have a younger Magnolia, slugs will try to eat the new fresh leaves. You can add slug pellets to prevent them from munching away on your plants or you can pick them off by hand. Once you have a magnolia that is more than 5 years old this should no longer be a problem. Another way to stop leaves getting to your magnolia if by sticking copper tape around the top of the pot. This can be purchased from most garden centres and had proved effective as protecting potted plants from slugs and snails as they get an electric shock when they touch the copper tape.
Rabbits might eat through the bark, something you can prevent by adding a barrier or a low wire fence. Once the rabbits have eaten the bark they can eat through a significant amount in one sitting which could have fatal consequences for your Magnolia. Your best option is a preventative one.
If you notice the leaves on your Magnolia are turning yellow it is indicative of too much alkalinity which is usually unlikely for pot grown plants. Too much alkalinity is problematic because it prevents your Magnolia from absorbing the essential nutrients. Younger plants often naturally have yellow leaves when young which is not to be confused with alkalinity.
The Magnolia stellata is the best variety for growing in a container. This variety will reach a height of 2.5 meters and a spread of the same when grown in the ground and even smaller in pots which is why its such a good choice. It flowers between the end of March and April just when spring is getting on the way and people start venturing back into their gardens again. The flowers are pure white with very thin petals and a lovely scent. The leaves are green and they shed in winter as they are deciduous. The Magnolia stellata is tolerant of alkaline soil, does very well in containers, and has received the RHS Award of Garden Merit. You can also get a variety called Magnolia stellata Rosea which is very similar but has a pink tinge to the flowers.
Another variety is the Magnolia Susan which reaches a full mature height and spread of around 3 meters when grown in the ground and much smaller in containers. It blooms between April and the beginning of May just like stellata. The flowers are purple when the buds start to form and once the flowers are in full bloom they take on a beautiful pink. The leaves are green and they shed in the winter. This is another variety perfect for containers.
Overall, if you would like to enjoy Magnolias but you want a smaller variety that you can move around outside, or you simply want the ease of a container-grown magnolia, growing Magnolias in pots is fairly simple and if you follow all of these instructions you will enjoy beautiful flowers at the beginning of Spring.