Japanese Acer Tree - How to reinvigorate growth

pravjoy

Hello

We have a Japanese acer tree in the garden that was overshadowed and crowded out by a bottle brush on one side and a large bayleaf bush on the other. So much so that I did not even notice the tree was there until last week!

As a result, it looks like its growth has been stunted and it has not filled out or grown nearly as much as the acer on the other side of the garden. I have attached photos of both - as you can see, the other tree is twice as tall and filled out much more with thicker branches.

I can only assume both trees were planted at the same time (about 10 years ago) by the previous owners. But it could be possible that the second tree was seeded more recently by the larger tree?

I noticed a few small dead branches on the lower limbs that were not getting any sun, which I have cut off. I have now cut back the bottle brush and bayleaf trees to provide space for the acer.

Could you please give me some advice on how to reinvigorate the growth of the smaller acer? Is it worth trying compost or will regular watering suffice? The idea is to make the acer a feature tree at the end of our patio.

Many thanks for any advice and tips.

jamesharcourt

These are slow growing plants - you won't be able to fill out it particularly quickly.  

Not sure of the variety, but assuming it's Acer Palmatum Atropurpureum ... if so, it grows fairly vigorously and despite what most people say, these like as much sun as they can get.

The key with these trees is good soil with enough air pockets for decent oxygen exchange and regular water (as opposed to loads of water).

Re soil - normal compost on it's own is very often a bad thing, particularly in larger pots.  I'd mulch it with composted pine bark fines (referred to as pine bark "soil conditioner") and water with a liquid seaweed organic feed every two weeks through the growing season - and just use a moisture meter to ensure the soil right around it doesn't dry out too quickly. 

Don't overwater, this is just as bad as giving it no water.  This depends a bit if you're on very heavy clay soil which is bad for drainage particularly in winter.

Come the dormant season, I would then look at pruning to try to encourage back growth lower down.   I suspect it will just extend the branches it has at the moment if you left it - so personally, I would wait until Winter - during a dry period - and cut it low down above that lower section of growth - and seal the wound.  Then let it grow up from there, my Atropurpureum puts out upwards of 1' of growth a year with a lot of that coming in Spring.

pravjoy

Many thanks James for the advice

Fairygirl

@jamesharcourt has made a very good point re the drainage for Acers @pravjoy . Despite needing regular watering, they still need good drainage. In pots, it can be more difficult to achieve, and people often make the mistake of just soaking them constantly, forgetting that they don't like small roots sitting in permanently damp soil. It's also the reason why they should always be potted on slowly - not too big a jump in pot size at a time. 
That one has clearly got some good conditions at it's feet, and a bit of judicial pruning later will help. It should become a nice specimen again.
He's also right that although dappled shade is the ideal for virtually all Acers, the purple ones need enough light to give their best colouration. The amount of sun they'll tolerate is dependent on the other things being suitable. Exposure to lots of wind and soil which dries too rapidly, will affect that enormously. 

Fairygirl

@jamesharcourt has made a very good point re the drainage for Acers @pravjoy . Despite needing regular watering, they still need good drainage. In pots, it can be more difficult to achieve, and people often make the mistake of just soaking them constantly, forgetting that they don't like small roots sitting in permanently damp soil. It's also the reason why they should always be potted on slowly - not too big a jump in pot size at a time. 
That one has clearly got some good conditions at it's feet, and a bit of judicial pruning later will help. It should become a nice specimen again.
He's also right that although dappled shade is the ideal for virtually all Acers, the purple ones need enough light to give their best colouration. The amount of sun they'll tolerate is dependent on the other things being suitable. Exposure to lots of wind and soil which dries too rapidly, will affect that enormously. 

Fairygirl

@jamesharcourt has made a very good point re the drainage for Acers @pravjoy . Despite needing regular watering, they still need good drainage. In pots, it can be more difficult to achieve, and people often make the mistake of just soaking them constantly, forgetting that they don't like small roots sitting in permanently damp soil. It's also the reason why they should always be potted on slowly - not too big a jump in pot size at a time. 
That one has clearly got some good conditions at it's feet, and a bit of judicial pruning later will help. It should become a nice specimen again.
He's also right that although dappled shade is the ideal for virtually all Acers, the purple ones need enough light to give their best colouration. The amount of sun they'll tolerate is dependent on the other things being suitable. Exposure to lots of wind and soil which dries too rapidly, will affect that enormously. 

Fairygirl

@jamesharcourt has made a very good point re the drainage for Acers @pravjoy . Despite needing regular watering, they still need good drainage. In pots, it can be more difficult to achieve, and people often make the mistake of just soaking them constantly, forgetting that they don't like small roots sitting in permanently damp soil. It's also the reason why they should always be potted on slowly - not too big a jump in pot size at a time. 
That one has clearly got some good conditions at it's feet, and a bit of judicial pruning later will help. It should become a nice specimen again.
He's also right that although dappled shade is the ideal for virtually all Acers, the purple ones need enough light to give their best colouration. The amount of sun they'll tolerate is dependent on the other things being suitable. Exposure to lots of wind and soil which dries too rapidly, will affect that enormously. 

Dave Humby

You can say that again @Fairygirl

Just a quick add on pruning. This should be done in the dead of winter as Acer's 'bleed' heavily if pruned during the growth seasons. We are lucky to have two mature specimens here and one is in pretty much full sun all day....and loves it! We are the highest point around here and ex-gravel workings so it's windy and dry rubbish ground conditions. All in all the Acers should hate it but they threw out the rule book I guess 

micearguers

@pravjoy, @jamesharcourt one point regarding sealing. I thought this was a thing of the past, and that Wound cuts seal themselves, and applying a sealer can lock in moisture and decay. Is it different if you cut back the main trunk?

punkdoc

Sealing of wounds on trees is no longer recommended, it encourages infection, by locking in "badness".

jamesharcourt

I’ve had two Japanese Maples die from pseudomonas syringae or other waterborne infection - both times entering unsealed old pruning wounds already made by the arboretum, always low down the tree where dampness is more likely depending on tree position.  

Others I have spoken to do the same - selective sealing (based on cultivar - some are far more susceptible - and planting position etc.) - and have had nothing but healthy maples.

I don’t use it for pruning anything else though - and I definitely don’t use it when cutting off plants that have had disease.