Strange Acer colouring.

I have a rather lovely Acer which produces a nice reddish grey leaf.  Here is it exactly a year ago:




This spring, it sent out nice deep red new growth as normal, then for some reason it stopped. I put this down to our wet, sunless and very windy late spring/early summer as some leaves were showing signs of scorch.  I then put it into the greenhouse to give it some shelter for a few weeks during which time I fed it regularly with a weak Miracle Gro.  This seemed to work in that it has put on the growth it should have. 

BUT...

...the new growth has come in mostly green.  Here is the "today" pic:




My question is several fold and is one for the plant physiognomists I think:

1.  do the different colourings of maples depend on substances such as anthocyanins etc as per other red leaved trees?
2.  are these determined by sunlight levels?
3.  does the process need direct sunlight - i.e. could glass in the greenhouse have interrupted the formation of the red leaves by acting as some
     sort of barrier?
4.  or is it just a combination of things not mentioned above?

and more importantly, 5. will it revert to its "proper" colouring next year?


I should also mention that in the past month, we have had a period of good hot strong sunshine for most of the day. The tree was taken out of the greenhouse at the beginning of that as the temperatures would have cooked it.

Hi Fiona

It look like you have a nice healthy acer deshojo...take it back outside next year, and it will grow, and gain the collors it used too.

Kind regards Yvonne

Yes, it looks like Acer p. 'Deshojo': late growth in the season is usually not as red as in the spring. It coud be the explanation.

But there are hundreds, and perhaps even thousands of A. P. cultivars, not to mention those which are not from the true stock, have been misnamed, mislabelled, etc. So if one doesn't know what cultivar it is exactly, it's very difficult to give any precise diagnosis.

I wouldn't worry: colours can vary from one year to the other on many of them because of the weather conditions, the water pH, differences in fertilization, etc.

Very nice tree BTW, even if some could say that the top could be cut down a bit and be more rounded, but I like it like that

Temperature, ferts and sunlight would also impact on the colour in my experience.

My experience of deshojo maples tells me that the red colour lasts the longest in direct sunlight. Mine was left out last spring to break bud in the garden and was left in direct sunlight all summer. The leaves remained red all season. In a very cloudy summer the leaves will fade to reddy green as summer progresses. This year because of the late cold snap it was kept in the polytunnel until several weeks after leaves came out and as such the shady conditions meant that the red started to fade before I felt confident enough to put it out. Since then it has stabilised as a reddy green and not gone any greener. You will notice that any new growth produced during summer will come out bright red so if we have another late spring then a defoliation in late spring will restore the bright red if its that important.
The most conclusive evidence regarding deshojo involves my mother in law who was convinced she could keep one in her lounge. It came out bright red but within a matter of days it had faded to green in the unnatural shaded conditions and by June it was thinking it was autumn and began to lose leaves. That's when it was given to me to save and it is still going 12 years later but now lives a more normal red life on the patio.

Thanks for that, it makes sense in a general way.

What I'd be interested in having confirmed is if indeed the glass of the greenhouse acted as a barrier to the sunlight (e.g. changed the wavelengths/intensity or whatever) and that is what caused the new growth to come in green rather than red.  Please note that the "normal" colour of this tree is a red-grey rather than the all over red you get on a lot of deshojos.  It was its more unusual colouring that attracted me to it.   

What I'm doing now is keeping a close eye on it to see what colour any new growth I get is now that it's outdoors in full sunlight - and amazingly we're having quite a bit of that.

Fiona,
Is it a genuine grey colouration, or do the leaves just look a bit pale and washed-out?
Reason I ask is that I have a big Shindeshojo (in ground) that ends up looking a bit pale and chlorotic once the first flush of colour fades. It's in full sun at the front of the house. My Deshojos, round the back, get afternoon shade and are still much redder.
Your first picture looks similar to my big one in some ways.

Yes, the color might be affected by the greenhouse glass.
Yes, the color is due to anthocyanins and other pigments.
One factor not mentioned was night temperatures. The strongest leaf coloring in most red-leaved plants occurs when days are hot and sunny and nights are cool.
Iris

Tom, it's a genuine grey-red colouration - you can see it more clearly in some of the leaves in the first pic. It is almost like a vareigated leaf.  It is not that result of chlorosis.

Iris, well we certainly get the coolness at night here and in a "normal" summer, we obviously get enough sunlight and heat.

I can confirm that uncoated greenhouse glass will transmit light at different wavelengths in equal quantities but there will simply be less of it at all wavelengths. This suggests that the only difference between outdoors and in a greenhouse is less light. Ie more shade. I can say this because my day job is applying specialist coatings to lenses used in optical systems mainly for military purposes.
A couple of years ago I left a deshojo on the bench in full sun but failed to turn it all summer. The result wad ref foliage on the sunny side and green leaves on the back. This shows that even with maximum exposure to daylight in full sun the difference which you would think would not be that great has made a difference. I would expect to lose a lot more light through "dirty", low quality greenhouse glass so the difference in greenhouse foliage colour will always be noticeable whatever you do.

Thanks for that.       My friend who also works with specialist lens coatings said exactly the same thing.

more nitrogen or just more fertiliser than normal changes leaf colour and colour intensity too - my big one goes greener quicker in the greenhouse than it does on the bonsai bench under shade netting though, which is odd as apparently it should stay red longer in the shade. mine always gets defoliated each year too and the second set of red leaves appear early summer but never stay as red for as long in the summer light intensities. 1st spring colour holds for 6-7 weeks, the new leaves that follow defoliation are usually red for just 3 weeks. mine may be beni maiko, if not shin deshojo - virtually impossible to tell even though it is a long ago grafted imported tree.

i think red acers are actually becoming much stronger and doing well when the leaves are green - they (the green leaves) are certainly giving more to the plant than red ones. this has been a great year for growing bonsai - best out of the last 10 for sure , i have high hopes for great autumn colour if we get a nice chilly snap too.

cheers

here we go - my tree been in greenhouse all year up until July 6th


then on the shaded bench from 6th until 18th July and it goes green !


recovering from a rampant aphid attack on the bottom branch too - odd little white ones wilted all the tips of every shoot on the one branch but were not on any other tree or any other branch of this tree - they died in hours after a normal spray treatment too - very annoying

Thanks , Marcus.

Interesting. It may have been the combination of the greenhouse and the aggressive feeding that has brought about the difference.  

The main thing is it's doing well now, irrespective of its colour. We'll see if there is any reversion to red as our sun intensity starts to fade. It is certainly far more sunny than it was last year.


btw I almost never defoliate trees up here as our growing season is so short, not to mention wet.  I know some people who partially defoliate and I've never been convinced that it has achieved anything.

fiona wrote:
btw I almost never defoliate trees up here as our growing season is so short, not to mention wet.  I know some people who partially defoliate and I've never been convinced that it has achieved anything.

On my maples defoliation is done in different ways to achieve different goals. Between late feb (kiyohime) and early April all the acers leaf out. If I need to build more inner ramification from new buds I fully defoliate the tree after 6 weeks in leaf, this makes new inner buds form and open while the tree is also opening outer buds that were at the leaf bases. These trees then need a second treatment to let light reach the new small shoots - outer leaves are reduced to 1 in each pair, then the 1 leaf cut in half - this work on the outer canopy reduces shading but doesn't trigger buds to open at the leaf bases again.

on trees that will need old outer branch sections cutting back to already present inner shoots i will defoliate totally the outer growth but leave the inner leaves. this gives the inner shoots a boost in strength as they see some light and get all the growth time while the tree starts to open outer buds again. this method makes outer ramification better too as a small shoot grows where before there was just a leaf

once a tree has ramification you are happy with from inside to out, and most importantly short node length on all sections of the branches defoliating is not needed - now it is essential to do the leaf pair reduction to one and the cut in half method - this is the only way to get light in so the inner shoots remain healthy and critically they maintain short nodes - if the outer tree is too dense inner shoots extend like mad to reach light and the entire years growth needs cutting off at the base and doing again - this undoes all the work and puts the tree back where you started.

it only takes 5 to 6 weeks to complete the cycle and it improves the tree hugely as the last thing we want is strong first flush growth making up the branches - nodes end up 4 or 5 cm long (or worse) which is way too much. The second bud growth is less vigorous and builds better branches on trees you want to refine. You also extend the growing season too as the new leaves are in better condition and stay on the tree longer so i'd say it was essential in locations with poorer weather.

try it, you'll be happy with the results as long as you do it early - leave it until late and you get bigger leaves sometimes.

cheers

Hi Marcus

Well said about defoliation, this how to maker better bonsai, and the reason why we do it  

Would you think, the lowest branch on your acer was attacked, because the lowest part is small and weak, compared to the rest of the tree?

Kind regards Yvonne