Hedge sharing ground with tree roots

Hi,
I planted a row of laurel hedging back in Autumn 2014, they were potted plants about 2 to 3ft tall. I planted them in between some mature trees, noticed a lot of tree roots when I was planting, dug around them to put the laurel in. I watered them well for the first year, ground has good drainage. I've been fairly vigilant weeding around them.

The hedges are surviving at best, certainly not thriving, got zero growth last year. Reading up a bit I see that the tree roots could be a problem, taking all the nutrients. I did not fertilize them at all as I was told this was not really necessary for hedges. I am wondering how best to treat the hedges this year considering they are sharing the soil with some trees. I was thinking of putting down some of those chicken droppings pellets...good/bad idea? Any other advice?

thanks.