It is loss of chorophyl in the leaves.

But what happens to the chlorophyl?
I've been watching a variegated plant I discovered. Some of the foliage emerges green, some yellow. The yellow slowly lightens to pure white and then after a time kind of crinkles and dries up without discoloration. Is this due to the chloroplasts bursting? The leaves are very thin, so maybe the chloroplasts make a significant structural difference to the leaves. Today I realized some of the yellow foliage is also darkening to green after emergence. Are these chloroplast developmentally disabled, getting off to a late start somehow? Then there is the foliage that emerges green and seems to be stable. Its hard to imagine all these different things going on in one plant.

Howdy Hoe,

This Nutrient Troublechart might help you figure this out.

Take a look and see if the newer or older leaves are affected. Generally speaking, plants will sacrifice old leaves in favor of new growth. Some of the minerals that the plant needs are moveable. So if the plant cannot find enough of a particular mineral in the rootzone, it will harvest the mineral from its own older leaves, transfer from one part of the plant to the other.

Without seeing the plant, I cannot say that this is what is happening in your case, but I think if you observe the plant with this new knowledge, you may have a better shot at figuring it out.

Hello all, I think all of you are missing the point of Hoe Hoe question. I think the question is more of what causes yellow variegation and what causes white variegation and why does some plants switch between the two. My experience with this has to do with a plant that was normal green, mutated into a yellow/green pattern, then from there went on to a white/green pattern. If the plant constantly does this, my belief(I will admit I know very very little about botany) is that the mutation is a bit unstable. There's a article in the link below that talks about chlorophyll and xanthophyll. here's a quote "Variegation in leaves is caused by a loss of light absorbing pigments in the plant cells. Remove only the green chlorophyll and the result is yellow variegation. Remove both chlorophyll and the yellow pigment xanthophyll and the variegation is white. Yellow variegated leaves are still quite efficient at using the energy of sunlight to produce sugars."

Here is a link that might be useful: chlorophyll and xanthophyll

thank you Admmad. That is a great explanation. It also explains another variegation question I would of had too. ThankS!

The color change you describe is particularly common in Hostas. Yellow variegation will often turn green over the growing season, or if exposed to sun, yellow frequently bleaches to white. And, as you describe, white colored areas burn in the summer heat. That's why many of the Hostas with white variegation do not grow well in southern gardens. The quote below is from www.emilycompost.com under "Foliage Coloring".

Three terms are pertinent to the culture of hosta, that sometimes make them chameleon-like in growth behavior. It is basically a color instability. Viridescence, will happen when a yellow center will gradually turn green as the season continues. This term also applies to when a white leaf turns green. Lutescence happens when a hosta will begin green and turn to a shade of yellow as the season matures. The third color changing term is albescence. This is when yellow area turns white. It is important to know that this is a normal thing.

As for why this happens, admmad gave a great explanation.

Here is a link that might be useful: emily compost