Trees don't really need any amendments. You should have posted this in the regular forum and not the gallery section because you don't have a picture.

As for the droppage...it is pretty normal if you plant a tree in August for the river birch leaves to yellow and fall off. They all won't, but that is the main thing they do to fight off uneven watering or any such stress. I think mulching them would be the best idea. And watering really well especially in the fall. They are river birches afterall. good luck!

Sounds like a terrible planting job. How deep were they planted? That's usually the problem (with too much or too little water a secondary problem). Sounds like your trees are in bowls, and your watering may be keeping the roots too wet. Have you checked the soil moisture before watering? I'd give them a call back and have them plant them right, using info from treesaregood.com. JQ is right, too. Transplanting trees in the summer will cause some stress.

My guess would be to water them plenty.
At nurseries they water their stuff ALL the time so everything looks healthy and lush for customers to see.
After plants get bought from these stores they still should get lots of water for a while.
I've bought I don't know how many potted plants that died after I brought them home for seemingly no reason.
Then I got a part-time job at a nursery where my biggest task was watering all their plants for like 3 or 4 hours a day.
They'd even tell me "now water the big ones till water comes out the bottom".
Yeah, the transplant shock could also have something to do with it.
I always thot that the planting hole should be like 3 times the size as the root ball part.

I have the same situation now with my newly (5 days) planted river birch. also about 10' tall. Please tell me if yours survived and did you do anything more to help it?

Just curious chi, was it balled and burlapped when you bot it or did they dig it up?

it was balled, and burlapped

Why would you try to plant trees in August (except in a climate where that is the rainy season)? You plant trees in the fall or earliest spring, not in the blazing hell that is August. Certainly it's possible, but it's not a good time.

chi, what kind of soil do you have? Sandy soil with good drainage will take regular watering. A heavy clay soil with poor drainage will hold water like a bath tub and will keep the roots drowning in water if watered too often. The results look the same whether too much or too little water. You'll have to figure it out according to what type of soil you are talking about.

Unfortunately chi, I think you no longer have a ten foot tree, maybe a 2' or 3' tree, (unless you take it back). Reason I think that is I've seen that happen to River Birch here too. They're big 20' multi-stemmed tree turned into a single stem 5' model, I'd be pissed.

Imo, I think nurseries let the small feeder roots grow thru the burlap into the soil, then yank up the tree and mess the tree up.

Waiting to see if it is shock from transplant. Soil is good black dirt with drainage and is on lower level ground that has lots of water. Not too dry but does drain out . If it does not recover, they will provide another by Spring and hopefully it will work. So we wait and see....