Anyway when we came back they all looked dried out and dead. Upon closer inspection, 2 of the three have a few green healthy looking leaves and canes, and one looks completely dead.

Are they history? Should I cut off the dead parts of the ones that have green, or wait until fall? Is the dead looking one totally dead?

One thing I did not do was separate the roots when planting--the instructions didn't mention that, but I see it now that I am reading here. (Note to self: next time read Garden Web forum BEFORE planting!!)They didn't seem too rootbound, but maybe this killed them?

Help please, and thank you!
I'm in mid missouri, and daytime temps are in the mid 90's.

Ren920

its a bit early to start hacking them up ....

find the receipt if you have a warranty

ken

May is pretty late for planted trees and shrubs. With pot-grown material, it is do-able, but isn't ideal. It certainly requires diligence with monitoring soil moisture and watering when necessary.

I planted according to the directions on the tag, and prepared the holes well, backfilling with a mix of bagged topsoil, compost, and native soil.

The instructions you depended on were incorrect. It is almost never a good idea to amend backfill soil. Whoever wrote those instructions apparently didn't know much about planting woody plants.

"I watered them after planting, but then we left town for 8 days."

Without knowing what type of soil and drainage you have and how much it rained, we can't know much about whether this was a problem, but it definitely is a red flag.

"One thing I did not do was separate the roots when planting...maybe this killed them?"

I'm not sure exactly what you did from your description, but you probably helped your lilac more than hurting it by addressing any pot-bound roots. I don't think your problem lies here.

As Ken said, find/keep that receipt if you have a warranty! Check out the link below for future plantings.

Tada! Now we have the oft claimed "transplant shock."
But no. Not shock at all.
Instead, drought stress because the roots are dry.

Neither of these assumptions are always the case. Roots are only confined to the rootball if the root ball was not disturbed (which Ren920 actually claims to have done). Rootballs only dry out before the surrounding soil if 1. pore size of rootball material is larger than pore size of surrounding soil AND 2. moisture is insufficient to keep the rootball moist.

"...water won't go sideways into the rootball."

That statement is just false. Capillary action (a major component of internal soil drainage) can move water sideways (horizontally) equally as well as it can move water vertically.

"Tada! Now we have the oft claimed transplant shock. But no. Not shock at all. Instead, drought stress because the roots are dry."

This may indeed be the case, but we have little if anything to base this conclusion on, at this point. Unless you have a crystal ball, you are jumping the gun BIG TIME!

Anne