I can find 21 of them, I'm not sure what happened to the rest, I think they got dug up and eaten. Those that remain show serious signs of having been nibbled, probably by a hare or rabbit. The hot dry Spring didn't do them any good either, and some were showing signs of drought damage. There are some self-seeded Walnut trees in the field too, and even they are showing some dead leaves that came out too early and dried up.
I decided to make an effort to water the new trees frequently to protect them from this hot weather. I started out by carrying two watering cans across the field, putting half a can on each tree. 6 return trips, it took an hour and a half, and made my arms ache. I needed a better option if I am going to be doing this all Summer.
Here is the solution. I have a sit-on mower, 22 horsepower, with a towing ball on the back. I have a trailer that it can pull, and a couple of plastic dustbins that I used to store Dahlia tubers in over Winter. Put the dustbins in the trailer, fill them with water and use the mower to take them over. When in place, use the watering can on the trees.
For the nibbling problem, I spotted an ad in the French national small ads website leboncoin.fr, for some used tree protectors: thick plastic mesh, and poles for support. Perfect, €1.50 each.
As an aid to getting the mower over my unkempt field, I asked a neighbour to come and make a path around it (leaving the trees that are in the path; I can weave around them) using his 100hp tractor and flail mowers. It worked a treat, and I can now get the trailer all around the field with no problem.
The trees are responding to the water, and all, or nearly all, are showing signs of new growth. You can even see that the grass is greener where I have been watering.
My Husqvarna mower has done good service over the years. It has needed its share of spare parts, but then I haven't been gentle with it. Truth is, though, I should have bought a small tractor instead, a diesel, one that has a central mowing deck like the Husqvarna, but that has all the other possibilities of a tractor. It would have cost about 7 times the mower though, and at the time I never even thought about it.