Acer or Maple trees come in many cultivars with dramatic foliage in various shades and colours. Some grow very tall, whereas other species are suitable for container gardening, due to their manageable small size. One thing’s for sure, whether it’s a native Field maple tree (Acer campestre), Norway maple (Acer platanoides), Sycamore maple (Acer pseudoplatanus) or gorgeous Japanese maple (Acer palmatum), which can easily thrive in a pot, an acer tree can be always a beautiful focal point in your garden if you show it some TLC.
Acer species are relatively easy to grow, once established, but they do suffer from some problems, due to disease, environmental factors and in that sense, due to one’s lack of knowledge on the specific growing conditions a particular type prefers. On that note, our post will focus on the common problems you may encounter when growing an acer tree in a container, as well as on some general issues that could pose a challenge to your woody plant.
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In Britain, one of the popular acer tree variety that can be grown in a pot is Japanese maple. It comes in many subspecies, which boast distinct-shaped leaves in various hues. Its delicate foliage commonly tends to suffer from weather-related problems or wrong growing conditions.
So, if you notice one day that the leaves have suddenly started to brown, curl up or shrivel and the lower branches look as if dying, your potted acer tree has a problem, especially if the variety has overly dissected leaves. Experts refer to the condition as leaf scorch. The cause is most likely excessive exposure to dry winds, direct sunlight in hot summer or frost in the winter.
Also, excessive watering doesn’t do any favours to your potted Japanese maple tree, either, as this type of acer plant doesn’t thrive in waterlogged soils. To be fair, it neither flourishes in heavy shade.
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Now, let’s look at some other issues that may affect your acer tree, be it a potted Japanese maple or another variety that you’ve planted in the ground.
Galls (mites) can affect various acer plants, including Sugar maple, Red maple, Boxelder maple and Norway maple. Depending on the type of galls, the leaves of the plant can be covered in velvet patches, pimples or worm-like protrusions.
Pear thrips are winged insects, which lay their eggs on the plant. In spring, the larvae will feed on the leaves, causing their discolouration. Sugar maple is prone to a pear thrips infestation.
If the infestation is in an early stage, you can successfully treat it with a homemade natural pesticide. We have collected our favourite recipes in this post. Feel free to test them out.
With basic acer tree care you can fix and prevent the most common issues with your potted maple plant, which are not related to a specific fungal infection or an insect pest infestation. Those are best treated after a professional inspection by a specialist, as the solution is always individual and depends on the type and the severity of the condition. The prevention and care tips below will help you fight environmental causes for leaf scorch and generally improve the well-being of your Acer palmatum tree, especially if you’ve decided to grow it in a container.
Japanese maples thrive in slightly acidic, sandy, water-retentive soil with good drainage. Choose a good-sized pot that has a sufficient number of drainage holes to avoid waterlogging of the soil. Note that loam-based compost for acers is the best growing medium for your beautiful maple tree (ex: John Innes No 2). Furthermore, it’s recommended that you repot your Acer palmatum approximately every 4 years between February and March. As the leaves emerge, you can give your plant a balanced feed, as well. If you’ve never grown a Japanese maple in a container, follow these easy steps on how to plant an acer in a pot.
Mulching around the trunk of your Japanese maple with organic material, such a bark mulch, or with gravel slates will help the soil retain its moisture, especially in hot weather, when you are advised to water the plant a couple of times a day. Make sure that there is some space between the tree and the mulch, however. Again, protecting your acer tree from losing water and drying out is not only a preventative measure against weather-related leaf scorch, but can also reverse leaf damage if the problem is not yet too far gone. In addition, any steps towards enhanced water-retention of the soil will prevent it from case-hardening around the roots, by keeping the growing medium crumbly, but moist.
Finding the right position for your potted Japanese maple is important to avoid the onset of leaf scorch. This means that your plant should not be placed under direct sunlight in hot weather. A semi-shaded spot in your yard, which is sheltered from high dry winds, is the ideal environment for a healthy and flourishing acer tree. You can also resort to using a temporary windbreak around your potted acer plant during unexpected stormy weather conditions.
In winter, to prevent frost damage, cover your plant in a protective insulating material – a large box, placed carefully over a young plant, overnight, will do. Note that experts do not advise to bring the container indoors, as the difference in temperature when you move the plant in and out, can do more damage than good. Defoliation is a common outcome when contrasting temperatures are at play.
Pruning your Japanese maple is only necessary to achieve an aesthetically balanced shape of your plant, as new shoots usually grow in one direction. The task is best completed in late summer or early autumn. Remember that pruning in the wrong time of the year causes bleeding. Still, if your potted acer tree suffers from mild dieback and browning leaves and branches, pruning those will improve the overall look and state of the plant. Naturally, however, you will need to find out the underlying cause for the poor health of your maple tree.
A more specific pruning procedure that requires some knowledge and skills is root pruning, that can be done when it’s time to replace the soil or sometimes when you replant the acer tree in a larger container. You should prune the roots only lightly while cleaning them off any dry and hardened-up old soil.
Potted maple tree problems are often preventable by applying vigilance and the right care:
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Have you had any experience with growing potted acer trees? Let us know in the comments below!
Image source: Shutterstock: By Vahan Abrahamyan
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