Plants chickens WON'T eat

In short the only things I can think of are nettles and dock leaves 

my girls don't like mint, although they do sometimes give it a try!!  make sure its an established clump, i dug an old root from the veg patch and got it going in a large plastic pot first with large stones covering the soil so they can't turn it into a dust bath!!  they don't seem to eat established tomato plants either, but i put them up a bit higher so it's an effort for them, just in case.  good luck

yup, nettles and dock are about all that will survive!

Having said that, there's a couple of potatoes in my hen run that I clearly missed and they haven't touched them, plus the soil should be nicely fertilized to give you a good crop! 

I have 3 raised beds in my hen run but I have put chicken wire around them to stop the chooks getting in and digging up the veg and making dust baths out of them! 

One of mine destroyed a Christmas cactus yesterday so you can cross that off the list.

there's a few shrubs in my garden that the girls haven't gone for, choisya, viburnum, budleia, roses, hebes, photinia, kerria japonica, maybe because they have quite a large chunk of the garden to free range in, and the beds are quite big, they are more interested in the bug life underneath the shrubs  could be different story if there was only one shrub in their run,  sounds like your run is pretty big if you've got a cherry tree and rhododenun in it 

ours dont like marigolds or roses 

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