Autumn Colour 2011

[Webos]

Gday Guys,
I read somewhere that the Autumn colour in Deciduous trees is related to how fast the temperatures change between summer and autumn. So if we go from really hot conditions to cold conditions in a very quick period of time, the Autumn leaf colour should be very strong. This year in victoria, we have had a very mild summer with just a few days over 30. It will be very interesting to see how the trees colour up this year.

Anyone out there have any info on deciduous Autumn colour and how it works??

[Handy Mick]

Webos,
I thought it was due to the difference between night temp and the day temp, and maybe the length of day.

Mick

[Webos]

You may be right Mick. This is just what i read...I'd be very interested in knowing the truth

[Matthew]

Webos im not sure how it works but i thought sunny days and cool nights are what will give the best colour. with the rain this year im not sure how it will effect it, time will tell. One bonus is not a single tree has any leaf burn this year which does improve colour. Things turning here already are popplas, some creepers (virginia and bosten), some japanese maples just showing tinges, flowering cherrys. the nights are warmer for the next week or so (above 10) so its a guess this year. last year i didnt notice good colour untill late april ,may.

[Ash]

Living in the tropics I have absolutely no experience with autumn colour and plants. But I wanted to ask a question- do any of you attempt to control factors like temperature and day length to induce or improve foliage colouration?

The reason I ask is our winters up here are often too mild to stimulate flowering in some native orchids we grow (the ones from up in the hills). For example Dendrobium speciosum flowers in response to cool nights. Some growers (myself included) have experimented with placing the potted plants on a high concrete topped pedestal in the sun during the day to warm it up, the high thermal mass of the concrete warms the roots. Then after dark place it on a the ground on a concrete paver (after it is cool to the touch- you may wet it to get it there) which also has a high thermal mass and gets much cooler by dawn.

People who grow Zygocactus much around with day length- covering the plants with cardboard boxes early in the afternoon and then taking it off an hour or so after sun up to induce flowering. Some Sarrecenia and Dionaea growers in the tropics bare root their plants and keep the tubers in the refrigerator to simulate a cold dark winter.

Does anyone do it for autumn colour?

Ash

[bodhidharma]

G'day Ash, the only thing i do is keep my trees in shadehouse conditions in Summer and then move them out into full sun in cooler conditions. This year though we have had fairly cool conditions all Summer so i think colour will be anyone's guess this year. It will be interesting to watch.

[Kyushu Danji]

Considering the fact that in places like northern europe and canada (I'm not mentioning japan because summers there can be severe), where many of the deciduous species are from do not get the hot summers we tend to get, and get far more rain, I don't think this year's lack of searing heat and increased rainfall should have such an impact on autumn colour.

[dragon]

hi all
i heard that if you shorten the day the plant will get tricked it is time to change and
to get the leaves on your maples to go the red you place them in a dark cool area
so i had a small maple and thought i would try it and sure enought it worked
the leaves went red haveing a old fridge in shed turned on and placed small maple inside
every night for 2 weeks the leaves did go red so theory has it place in cool dark area and they will turn
cheers dean

[Craig]

Hi all, this is an extract from Bonsai-its Art,Science,History and Philosophy,By Deborah R Koreshoff.

this chlorophyll is situated in chloroplasts-small structures within the leaf that are like minute factories producing sugars from the suns energy as well as carbon dioxide,water and minerals,in order to feed the plant. Chlorophyll, being an unstable chemical is continually breaking down. However, in the active growing season, providing the plant receives sufficient light, the chlorophyll is being produced by the plant in adequate quantities to replace that which is being broken down to colorless compounds. The plant, therefore, retains its gree coloring.
With the cooler weather of autumn, this production of green chlorophyll is retarded in some trees and finally the stage is reached where it is being destroyed fster than it can be produced. When this occurs, the pigments formed by the chemicals know as carotenoids(carotene) and anthoxanthins(xantophyll) become apparent and the leaves take on a yellow to orange hue. These colors have been present right through the growing season but the production of the chlorophylls in the warmer seasons masks these weaker pigments.


In some types of tree a slightly different process occurs,With the onset of cooler weather,pigments known as flavinoids:floavones and anthocyanins, are produced through the action of sunlight on excess sugar and waste products that are trapped within the leaf.In the growing season, the leaves produce the sugars during the day and these sugars are transported during the night to be stored in the stems and roots.When autumn comes the day temperatures are usually warm and the weather is sunny so that sugar production continues.The night temperature, however, are usually cool and particularly when the temps fall below 9 degrees celcius, the biological processes of the tree are slowed down and,as a consequence,the tree is not able to move out all the sugars and waste products produced by the leaf during the day. 7degrees celcius seems to be the temp where this movement ceases altogether.If these sugars were left in the leaves, the pressure in the cells would become so great that the cells would be destroyed. As a solution to this problem,the plant converts these sugars into quite harmless pigments,that is,flavones and anthocyanins. These pigments produce the spectacular reds and purples, and are a result of pigments specifically produced in autumn, rather than having been masked by chlorophyll in the growing season.

To produce the best pigments, just when the leaf reaches proper maturity, five to seven consecutive nights of cool or frosty weather are necessary, while the days are warm sunny and dry. if the plants are overwatered at this stage, or if continued rain occurs, the more rapid movement of sap within the tree counteracts the entrappment of sugars in the leaf. Consequently less coloration will occurs.


Hope this is helpful ,,,Regards Craig

[Kyushu Danji]

Interesting stuff, reminds me of my high school chemistry class though o_O

[leamos]

Colour will depend on temperture, levels of sugars in the leaves, amount of autumn rain and day length

[Craig]

You may be right Mick. This is just what i read...I'd be very interested in knowing the truth

[Kyushu Danji]

Definitely getting some reddish tinges on my dogwood.

[dragon]

hi everyone
i have started to notice that on a few of my maples the leaves are starting to go reddish
where as temp here has dropped a little in the last few days and with one of my maples
i have been putting a plastic black garbage can over it so it shortens the days for it
and it has gone reddish more than the rest
cheers dean