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Re-potting Japanese Maples

Re-potting Japanese Maples
Japanese Maples grow beautifully in containers

Japanese Maples look fabulous growing in a container but every so often they will need a little more growing room for their roots. Follow our simple guide to re-potting your tree to ensure it is happy for the next few years…

When should my Japanese Maple be re-potted?

The best time by far to re-pot a Japanese Maple is early Spring, just before the buds begin to burst into life. The reason for this is that the days are starting to increase in length and the temperatures (hopefully) are beginning to rise, meaning that your Japanese Maple is beginning to wake up from its winter slumbers. The roots generally begin to grow before the leaf buds and so, re-potting now means that the plant will start to root out into its new compost more quickly than at other times of year.

We wouldn’t advise re-potting in April/May – this can be more stressful for your Japanese Maple as it is putting all of its efforts into producing new foliage and the shock of being transplanted at the same time can result in the spoiling of the leaves. This can be seen by black or brown tips to the leaves but isn’t necessarily anything to worry about, it just looks unsightly. This doesn’t happen on all Japanese maples but it is worth bearing in mind.

You can re-pot through the summer months as your Japanese Maple will have done a lot of its growth by then and will happily root into fresher compost. However, if you re-pot in the very height of summer when temperatures can be at their most extreme, you may find that the foliage shows signs of stress as it struggles to move enough moisture from the roots to the leaves. Again, don’t worry – keep the compost damp and the tree will be fine.

Definitely DON’T re-pot in the autumn. As the day length decreases and the temperatures begin to fall, your Japanese Maple is getting ready to go into hibernation. This means that although it may start to produce some new roots into the fresh compost you’ve given it, it more than likely won’t fully root into its new container. This means trouble. If it hasn’t rooted properly before the onset of winter (particularly considering our wet winters)

What compost should I use to repot my Japanese Maple?

Potting up Japanese maples
Japanese maples like growing in a free-draining compost

Japanese Maples like a free-draining compost that retains some moisture and has a good balance of air and moisture. We use a mixture of good quality peat-free ericaceous compost (it’s not vital but we find you tend to get better colours in the leaves) mixed 50:50 with fine pine bark and some slow release fertiliser.

The fine bark serves two purposes. Firstly, it creates air gaps within the compost to allow the movement of air around the roots and ensures that they don’t become waterlogged, as can often be the case in denser compost mixes. Secondly, the nature of bark means that it can also absorb and retain moisture that can be accessed by the roots, meaning the compost can be free-draining (excess water can drain through) but moisture retentive (doesn’t dry out too quickly.

How big should the pot be for my Japanese Maple?

GOLDEN RULE: NEVER OVER-POT YOUR JAPANESE MAPLE!

One of the biggest killers of Japanese Maples is over-potting. Don’t be tempted to transplant your tree from its container into something that is much larger, thinking that it will save you time in the long run. Japanese maples like to be re-potted in stages, going up in size a little at a time – somewhere between 50 to 100% wider than its current container.

For example, a young Japanese Maple growing in a pot that is 15cm (6 inches) wide should be transplanted into a pot between 22.5cm (9 inches) and 30cm wide (12 inches). For slower-growing forms and dwarf types, it would be best to err on the smaller jump in size as they can take longer to get settled.

What is the best type of pot for my Japanese Maple?

Glazed pots look fabulous and are ideal for growing Japanese Maples

Glazed pots would be my go-to choice when growing a Japanese Maple for the long term. Terracotta pots are porous and as such tend to dry out too quickly in the summer months which will result in a stressed tree – but absolutely fine for plants more used to Mediterranean climes such as olive or fig trees. Definitely avoid metal containers – they might look funky but in the summer, they get far too hot and can seriously damage the root system.

As for pot shape, try to steer away from pots that curve in at the neck as this will cause real problems when re-potting in the future as you may not be able to get the tree out without damaging the pot or the tree or both! For the weeping forms of Japanese Maple you may wish to opt for a taller pot so the branches can cascade over the edges but I would avoid a tall pot for a tall tree as they can be more unstable in windy weather.

Be sure to place your pot on pot feet that raise it slightly off the ground – this will help to ensure that excess water is free to drain away from the pot as well as help to avoid frost damage to the pot in the winter months.

And finally…

It’s worth taking your time and making sure you’ve got everything right from the compost mix to the type of container – the aim is to produce a beautiful, happy tree that will reward you for all your hard work. Good luck!

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How to grow Japanese Maples – our quick guide

Japanese Maples (Acer palmatum, Acer shirasawanum, Acer japonicum, Acer sieboldianum being the most well-known) have the rather unfair reputation of being hard to grow and this simply isn’t true if you follow a few simple guidelines.

  • They don’t require acid soil to grow and will be perfectly happy on most good soils.  Just avoid very chalky soils and areas that get waterlogged or incredibly dry.
  • They don’t have to be grown in the shade – almost all cultivars will grow well in a sunny position.  Those that are variegated or with pale yellow foliage will benefit from some shade during the hottest part of the day.  Purple leaved types need at least half a day of full sun to maintain strong colouring.
  • Never over-pot a young tree and only ever re-pot if the root system is well developed and holding together well.
  • The best time to re-pot is early spring, just as the tree is coming in to leaf.  They don’t require ericaceous compost but be sure to use a good quality, free-draining compost.  We use a peat-free multipurpose compost mixed with composted bark which helps maintain an open soil structure.  Air in the compost is just as important as moisture.
  • Ensure the compost stays damp (but not soaking wet) throughout the growing season – consistency is key!  As with any tree, the larger and more mature it is, the more tolerant it will be of erratic watering.  However, do remember that the better you treat the tree, the better it will grow and reward you for your kindness…
  • Young trees grown in pots will benefit from being moved somewhere reasonably sheltered from the worst of the winter weather.
  • Japanese Maples grow very well in containers and with the right care can be happy for many years (think Bonsai).  Having said that, they will always grow better in the ground;  they have access to everything they need (water and nutrients).  In a pot they are always reliant on a third party (you!) to remember to water or feed when necessary.
  • We recommend seaweed fertiliser as a feed – it contains all the normal stuff plus a whole heap of trace elements for excellent growth.  Don’t overfeed – once or twice a year is plenty for strong growth.
  • When planting in the ground, we strongly advise the addition of Rootgrow Mycorrhizal Fungi Planting Powder – this will create a symbiotic relationship with your Japanese Maple which will last its lifetime, making it a healthier and happier tree.  In fact, the fungi make the roots so efficient that fertilizer is not required.
  • Ensure the tree is watered well for its first season – until it is has established its root system.  It is better to give it a good soak once a week or so during dry weather than just a little every day.
  • Whether planting in the ground or in a container, please ensure that you don’t plant too deeply. Look closely at the base of the trunk and you should be able to identify where it starts to widen – this is known as the root flare and should be the finished ground level. If a tree is planted too deep, soil will be in contact with the trunk which can promote fungal diseases and attacks by pathogens.

I hope this has helped and answered more questions than it has posed! Please feel free to email or call us if you would like any further advice. Good luck!

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There’s no business like (flower) showbusiness…

After a few late nights of wading through paperwork and forms-a-plenty, we have now booked our flower shows/plant fairs for 2019. Only having exhibited our Japanese Maples for the last two years, we are still working out which shows suit us well. To that end, in addition to our ‘normal’ flower shows, this year we are excited to be attending some of the renowned plant fairs organised by the Plant Fairs Roadshow.

Floral-Fringe-Fair-Miles-Japanese-Maples
Floral Fringe Fair

You can see the whole list of our flower shows here.

We’ll be sticking with the black cloth displays as per normal, just as you would see in the floral marquees at at one of the big RHS flower shows like Chelsea or Hampton Court. It may look a little dramatic but there really is nothing better to set off the leaf colour of the Japanese Maples than good old black.

If you are planning to come and see us at one of the shows and would like us to bring a particular maple with us, just let us know and we’ll keep one aside for you. Think of it like Click and Collect but more analogue.