A few more points on keeping newly planted tubelings alive in extreme conditions.
Our regular planting instructions strive to be complete; but the reality is, the current record-breaking heat and drought are outside anything you could call "normal". We do have some additional experience that can help you in this situation.
A. Water deeply. If you are only able to supply enough water to get the ground wet down 2-3"; you might be better off not watering at all. Because: hazels normally grow roots very near, or even "in" the ground surface. Particularly when newly planted, they have limited resources to work with; if you are only watering shallowly, they will be encouraged to grow mostly shallow roots- following where the water is. They may not have energy enough to also grow deep roots. So- when it gets dry again- they will be stressed, again.
Try to deliver enough water so that the ground becomes wet at least 6" deep; 8" is better. This will encourage deep root growth- and down below 8" there will still likely be water available in the soil; and the roots will continue growing deeper.
B. DO NOT PULL WEEDS near your newly planted tubelings. Their roots are intertwined, and you will destroy some of the roots of the tubeling; it may not be able to recover in this extreme situation. You can cut the weeds off; but don't pull them.
C. NEVER HOE around new tubelings- the damage to their roots can be drastic.
D. DO NOT suddenly remove all weed cover, if the tubeling has been buried- it will burn up. If weed cover has become extensive, we cut off all weeds to the NE of the tubeling, leaving most of the weed shade to the south, west, and overhead. A little shade won't slow the tubeling down at all; and a little protection from drying winds and sun may actually help.
E. DO NOT let the tubelings remain totally buried in weeds - not only will total shade slow them; but the deep cover greatly encourages insects, which are safe from birds there. In particular, young hazels may be skeletonized by grasshopper nymphs - if buried in grass. Opening up just the NE side will drastically decrease grasshopper attacks.
F. If you feel you cannot keep up with watering in these drastic conditions; consider a) covering the tubelings with a hay/straw "hat", just during the extremes, quickly removed when the weather breaks; or even b) abandoning some of the planting, and concentrating on saving a portion of it- whatever you can actually deliver enough water to.
Even in the worst conditions- there are tactics that should prevent total loss.
G. CALL US - if you need advice. We'll try to help; and there are a few more tricks in our bag.