Photo-oxidation - aka sunburn. If you're interested in what happens during photo-oxidation: high light intensity levels w/o adequate amounts of protective pigments present can cause chlorophyll molecules to rise to a more excited state than normal. If light levels are high enough, the energy that is released as electrons in molecules return to their normal energy state may be sufficient to form oxygen (O2) radicals from regular O2. These O2 radicals are extremely reactive particles that readily destroy chlorophyll molecules. (This is the same O- radical that causes rapid oxidation [bleaching] in organic molecules when we apply H2O2 [hydrogen peroxide]). Evidence of the process is seen in a bleached or whitish/tannish/silverish appearance of the leaves, and is also often referred to as peroxidation.

Al

Hello Rose,

Good luck with your trees and getting the problem taken care of.

Al, that's interesting about the photo-oxidation and how it works. Does the wind add to the problem with sunburn on the plants?

Does the same thing happen to people, or is it a different scenario with people sunburn? Is it still photo-oxidation with us?

I've heard of windburn and have gotten it at times in the sun with the wind blowing hard. At least, that's what I've heard it called all my life. Does the same thing happen to plants? I know the wind affects the temps with winter damage.

Thanks,

noss

hey guys,

al thanks for the post! now the next question- what do i do about it?! haha i had worried it may have been something to do with the sun- it didnt look like the windburn i had last year.

i put them back on the enclosed porch last night to give them a bit less sun and wind... im assuming i should just more slowly acclimate the trees to being outside again?

thanks guys! :o)

rose

Hi Rose,

That's what I do--Expose the tender leaves to the sun a little at a time. If they don't have leaves yet, it doesn't seem to bother them, but if there are tender leaves, they'll burn in a heartbeat, especially down here where the sun is so strong.

noss

Rose,
To me windburn is a synonym for drying out. If there are enough winds, and the air is dry enough, it's possible that moisture can evaporate faster than it can be replenished by the plant. If this is the case try putting it on the leeward side of a building. As the air gets warmer and more humid, this problem should go away. But the leaves that are already affected will not get better.

If it is sunburn, which sounds likely given your description, probably the damage is already done, similar to sunburn in humans. Once you notice it, it's too late. As I understand it, new leaves will not be affected, since they will adjust to the full sun. So I would say that moving them back indoors is counterproductive. It will just mean that any new leaves that develop will adjust to the lower light levels, and then have an equally hard time adjusting if you put it in full sun again.

In the future try slowly acclimating the plant to the outdoors. Meaning, only a couple hours per day at first of direct sunlight, increasing over the course of a few days. If a plant wakes up early but is kept in a dark location, the leaves eventually will get so adjusted to the dark they will be unable to stand full sun. This is an undesirable situation, so try to either keep the plant from waking as quickly, or put it in the sun during the day at least when it starts to leaf out.

thank you both SO much for the help!!

i moved them back to the sunny enclosed porch just for a day or so... and will maybe put them out in a less bright location and gradually move them into brighter sun over the course of a few weeks.

right you are about it being permanent- some of the brownish leaves already died. fortunately, the trees are doing great and it was only a few leaves here and there that seemed that damaged.

i will also remember to take them out of dormancy slower next time. it was such an odd winter- i went into the basement to take them out of dormancy and they were already blooming!! crazy... but it should also hopefully equate to a nice crop this year before autumn comes. :o)

thank you!!

rose