based on the pix provided.. and your location.... as well as how big.. how planted.. native soil.. and amendments thrown in the hole.. and ambient weather ...

here is my suggestion:

ken

Sounds like your birch need to be watered. There is a reason it is called river birch.

Ken,

Was there a suggestion or are you asking for those details that you would like?

Embothrium,

I would be inclined to agree with you if the other six river birch that were planted at the same time were not thriving and growing. Also, we have been getting some really good summer thunder storms moving through the area and, according to my rain gauge, I have been getting about 1"-1.5" a week.

I have four river birch so am learning how to care for them. I know that aphids love River Birch. I believe morpheus (a pro regular here) said light application of soapy water helps rid the leaves of them. They don't seem to harm the roots or branches, but do turn leaves yellow with white powder. Of course it could be other like a fungus. That's why a photo may help. Curious its the two Betula nigra involved-perhaps less robust a species.

It may be overly simplistic to assume the trees are getting sufficient water just based on rainfall. There are all sorts of variables that could enter into the factor including soil type and water percolation, if the trees are planted on a slope, type of mulch used, runoff, etc. And soil conditions can change quite dramatically from one area to another, even within the same garden, so just because other nearby birches seem to be doing OK, it doesn't necessarily translate that the ones under stress are under the same conditions.

Newly planted river birches - and last fall counts as 'newly planted' - need a considerable amount of water to become properly established. This is a tree that will grow in standing water and is native to some pretty wet areas. And without a photo or any substantiating information to confirm otherwise - what Ken was alluding to in his post - your description of the trees and their "sudden drying" sounds more like drought stress/lack of adequate water than anything else.

Lol bboy, loved your comment.

I see more and more that idiotic landscapers are using these in hell strips, in yards with bad soil that people don't want to water, etc. etc. And they don't look good after dry spells. They are semi-drought tolerant when established - in the sense it won't kill them - but still not very drought tolerant. A big pair in my neighborhood when I grew up as a kid often lost their leaves in summer.