What is Wrong with These Trees/Bush?

[chiang mai]

We have thirty plus (phonetically) Sigh Gowlee (Banyan Tree Korean or similar) in one location, twenty in a diffferent one.

The first group form a hedge/boundary and are exposed to direct sun, the trees are about 2/2.5 metres tall.

Problem number 1: the leaves turn yellow and fall of, about 40% of them. Problem 2: growth at the lower levels is good, dark green and robust, growth in the middle is sparse and often light colored.

The second group of trees are in the shade and grow very well, there are no problems with this group.

These trees exist in all types of locations, shaded, direct sun, some watered heavily some not at all, all seem robust except the first group above.

Yellow leaves = too much water or not enough or poor nutrition, we've tried daily watering, we've tried urea and/or 16-16-16, all successful for limited time then the leaves turn yellow and fall off!

Currently I'm replacing the soil around these trees on the basis that it might be contaminated building site soil, any other advice?

Thanks

[samuijimmy]

I think if the other plants are doing OK, you will probably solve the problem with replacing the soil ...as you are doing.

It may take a while a month or two to see if it solves the problem, keep soil moist but not wet, for first few weeks.

Dig down far and wind enough to remove concrete or other undesirable materials in the soil.

It might help after replacing the soil to use Epsom Salts about 15 mils (a tablespoon) to about 4 litres of water ...

Or if you can find a water soluble fertilizer, use that, they usually have micro nutrients ... about every couple of weeks... early morning or late afternoon, but make sure to water before applying any fertilizer!

[steven100]

yellow leaves .... too much sunlight, lack of moisture under the tree.

[chiang mai]

Thanks for the ideas both but it remains very confusing. It does seem as though sunlight is an issue on the run of trees in question. Water: we've tried watering twice daily (on recommendation of a nursery guy) and we've tried withholding water but the results are the same, yellow leaves.

Yellow soft and spongy leaves sounds like too much water to some folks, don't believe this is the case here. Steven, can believe the too much sunlight part, not the lack of moisture however.

The run of trees in the shade is a real mystery, no sun and they're perfect yet these trees exist all over the place in a variety of locations, hmmm.

I'm midway through the soil replacement and will do as Jimmy suggests, was kinda hoping somebody would pop up and say ah yes, that's because...., oh well.

Oh yes, forgot to say, the the land the trees are planted in is covered with decorative stone, about two inches, the idea being to retain moisture in the ground - stone now being removed along with soil, grrr.

[samuijimmy]

Thanks for the ideas both but it remains very confusing. It does seem as though sunlight is an issue on the run of trees in question. Water: we've tried watering twice daily (on recommendation of a nursery guy) and we've tried withholding water but the results are the same, yellow leaves.

Yellow soft and spongy leaves sounds like too much water to some folks, don't believe this is the case here. Steven, can believe the too much sunlight part, not the lack of moisture however.

The run of trees in the shade is a real mystery, no sun and they're perfect yet these trees exist all over the place in a variety of locations, hmmm.

I'm midway through the soil replacement and will do as Jimmy suggests, was kinda hoping somebody would pop up and say ah yes, that's because...., oh well.

Oh yes, forgot to say, the the land the trees are planted in is covered with decorative stone, about two inches, the idea being to retain moisture in the ground - stone now being removed along with soil, grrr.

Sometimes answers are not always black and white when it comes to plant problems, but if there is a lot of stone underneath, then fertilizer is not going to have anything to "cling too" It just washes through.... as does the water!

I think the digging out the stone as best you can is probably the answer... You have figured it out...but just wishing there was a easier magic solution... methinks! ..... Get your shovel out!

[chiang mai]

Thanks for the ideas both but it remains very confusing. It does seem as though sunlight is an issue on the run of trees in question. Water: we've tried watering twice daily (on recommendation of a nursery guy) and we've tried withholding water but the results are the same, yellow leaves.

Yellow soft and spongy leaves sounds like too much water to some folks, don't believe this is the case here. Steven, can believe the too much sunlight part, not the lack of moisture however.

The run of trees in the shade is a real mystery, no sun and they're perfect yet these trees exist all over the place in a variety of locations, hmmm.

I'm midway through the soil replacement and will do as Jimmy suggests, was kinda hoping somebody would pop up and say ah yes, that's because...., oh well.

Oh yes, forgot to say, the the land the trees are planted in is covered with decorative stone, about two inches, the idea being to retain moisture in the ground - stone now being removed along with soil, grrr.

Sometimes answers are not always black and white when it comes to plant problems, but if there is a lot of stone underneath, then fertilizer is not going to have anything to "cling too" It just washes through.... as does the water!

I think the digging out the stone as best you can is probably the answer... You have figured it out...but just wishing there was a easier magic solution... methinks! ..... Get your shovel out!

3 metres done 18 metres to go, phew!

Thanks SJ.