Why is my new Acer tree dying?

Yep, that is a Japanese Maple, Acer palmatum

Here’s how to plant/grow a Japanese maple tree in a pot:

  • Prep:

  • The preparation necessary before attempting to plant. Make sure all of these steps are done/ready before you begin.

    • Make sure you have a pot large enough to accommodate the plant for at least a year. They will need at least 6 cubic feet (38 US gallons) of potting mix once mature. The pot should have at least one inch’s diameter worth of drainage per square foot of container space. More, smaller holes are preferable to one large one. Black pots should be avoided because of heat problems in the sun. Also, trees tend to prefer a shallow rooting, so a pot higher than it is wide will be beneficial.

    • Have the full amount of backfill mix ready before you plant. In a large container, it is useful to have a very free-draining mix. A base of coir (ground coconut husk) is ideal, because of improved fertilizer retention and lower acidity, as compared with peat-based mixtures. There should be at least 5-10 percent drainage helpers, such as coarse sand or perlite.

    • It is best to plant on a day which is overcast, so that the plant will not transipre too fast.

    • If the plant is potted, the roots may have circled the perimeter of the pot. in this case, it is best to score straight down the sides of the root ball in 3-4 evenly spaced places to about 1/2 – 1″ deep.

  • Planting:

  • Getting the tree in the pot – here are the basics you need to know.

    • Fill the pot with potting mix , up to the level of where the bottom of the root ball will sit. tamp firmly, to remove air pockets.

    • Place the tree in position in the center of the pot. Fill the rest of the way with potting mix, and tamp again. add more soil if necessary to level it off. Remember that the beginning of the root flare should be visible at all times. Do not bury it. Also, in a container it is not useful to plant high. The top of the potting mix should be level and even.

    • Water well, giving the tree a good soaking. The mix will be a little loose, so don’t aim a heavy stream at it. Rather, water with a trickle, and let it soak in.

    • Put some slow release fertilizer on top of the soil, so it can seep into the mix during rain. I’ve also had success using tree spikes.

  • Care/Maintenance:

  • For the established plant. This is the basic care required for general tree health. This does not cover pest/disease management, which will need to be taken care of case by case.

    • Never water if you can feel moisture when you stick your finger an inch or two into the mix. Overwatering and too much moisture are the biggest reasons I’ve seen these fail. If the soil is dry finger deep, give it a good soaking, and leave it to dry again. Constant dampness is not what you’re looking for.

    • Keep it in at least 6 hours of sunlight for best growth and leaf color.

    • Fertilizing can remain as replacing the extended release fertilizer when it runs out. I usually read the label, to find how long it was designed to last, and reapply about a week before that date is hit.

    • In winter, wrapping the pot in an insulator, and if you’re in a very windy location, putting a big box (large enough not to cramp the branches) over the tree will help prevent freeze damage.

    • Pruning isn’t usually necessary on these plants, but if you see a dead area, or a branch that is going way out of proportion, some light trimming will be necessary.

    • If the plant becomes root bound, which could take some time, if you can’t move it into a larger container, you will have to clean the roots off, and prune them lightly, enough that they will easily spread out in the pot. You can also take this opportunity to replace the potting soil. Do the root pruning and replant as fast as possible, but don’t go so fast you do a messy job. Cut back the top to mirror what you did to the roots, taking out only the branges with the worst placement. Try not to suddenly ex[ose a large area of bark, or you may get sun burn.

Your tree has a few issues. First of all, you should repot into a proper potting medium as soon as possible. The soil isn’t drying out properly between waterings, and the tree is showing signs of this (it can cause drying around leaf edges, while the plant remains unwilted). Also, the tree has been planted too deep for healthy growth. When you replant, make sure you can see the root flare.

Because of the time of year, you should keep the plant out of full sun for the first couple weeks after replanting. This will keep the tree from over-drying while it regrows some roots.

Your tree looks completely recoverable, it only needs a little proper care.

If you have any questions, or wish for me to expand on something or cover another topic, please let me know.

Acer palmatum

How many times have you heard a member of the Gardeners’ Question Time audience complain that their lovely acer has gone ‘all crinkly’ and died?

Just what is the secret with these plants? The RHS website describes acers as ‘easy to grow’. And they are when you know how…or rather, when you know where.

The best advice I was ever given was from nurseryman James Harris of Mallet Court Nursery in Somerset. Acers are happy in all soils, even chalky ones. Heavy clay can be a problem as acers dislike wet feet, so be sure to incorporate some organic matter into the hole at planting time. And don’t overdo the watering.

But, he said, if you remember nothing else, the single most important factor is shelter. And the more delicate the leaf, the more shelter it needs. Shelter means a place out of cold easterly and northerly winds and lingering late frosts, as it’s these two problems that cause the damage in spring after the new, delicate foliage has emerged.

Putting fleece over leaves if frost is forecast will help, as will providing shelter from overhanging trees, boundaries walls or surrounding buildings.

Japanese maples and city/suburban gardens are a match made in heaven, as long as the surrounding landscape has reduced the wind, and not created ruinous wind tunnels or eddies. Here, maples also benefit from the unintended side-effect of protection from unrelenting sunshine.

Golden and variegated types are scorched by hot sun and prefer dappled shade, though red and claret varieties are unaffected by sunshine, provided the soil is sufficiently moist.

A great spot is in the shelter of a tall tree, planted at the dripline where it won’t have too much competition from existing roots. This might mean digging out the lawn around an existing tree to create a new curved border for your acer. But it’s worth it.

Make it a few metres wide and long so it’s big enough to accommodate the mature plant, and to create an opportunity to grow other foliage plants, like ferns and heuchera or an oriental-style border with Japanese lanterns and stone bowls. You could add some evergreen foliage, though the maple’s deciduous outline is attractive in winter.

The decision on which variety to go for will be based on three things: i) how big you want your tree to grow – some reach 15ft (4.5m), whilst others stay a around a metre; ii) do you want an upright tree, or a mound shape – for mounds go for a dissectum. Finally it’s down to iii) colour and shape of the leaves. Do you want red, green or yellowish leaves? Or archetypal maple shape or fancy, lacily cut leaves?


‘Okushimo’ – unusual rolled-in edges to green leaves. Golden and yellow in autumn. Narrow, to 26ft (8m)

‘Senkaki’ – grown for its bright coral stems. Autumn colour ranges from golden-yellow to coral-red. Upright, to 16ft (5m).

‘Osakazuki’ – classic green maple turning a brilliant orange-scarlet in autumn. Upright, to 20ft (6m)

‘Bloodgood’ – deep red maple leaves like the Canadian flag. Stunning crimson in autumn. Upright, 16ft (5m).

‘Hana Matoi’ – a new variegated A. palmatum Atropurpureum Dissectum that has acer-philes excited: cream, pink and red in spring; red in autumn. Dome-shaped, to 6-10ft (2-3m).


‘Shindeshojo’ – gives you two bites of the cherry as it tints red in spring and again in autumn. Makes a small, layered shape, to 6ft (2m).

‘Katsura’ – unusual orange-edged leaves from spring to summer. Fiery red, orange and yellow in autumn. Upright, 10-14ft (3-4m).

‘Seiryu’ – lacy green leaves, tinted glorious red in autumn. Very classy in a black container. It’s an upright grower, 6-10ft (2-3m).

‘Deshojo’ – like confused traffic lights, this turns from amber in spring, through green turning red in autumn. Upright, to 6ft (2m).

‘Crimson Queen’ – lacy, wine-coloured leaves, gorgeous in terracotta or white stone. Scarlet in autumn. Dome-shaped, to 10ft (3m).


Mallet Court Nursery
T 01823 481493, www.malletcourt.co.uk

Big Plant Nursery
T 01903 891466, www.bigplantnursery.co.uk

By Lisa Buckland

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