Hello,I planted a beech hedge last year

Not sure what the green powder is other than some kind of fungal growth, but beech come into leaf very late, and very dependent on the weather, so you shouldn't be expecting any growth yet. Get worried if there's nothing by late April.
(We used to have a beech hedge all the way round our property in the UK; very good plant but a huge amount of work cutting it every year. I seem to remember always waiting for it to come into leaf in spring. Sadly, beech won't grow here as I think it must be too dry.)

Thanks for that, why do you consider beech harder than other hedge types? We have about 120 ft of the new beech and are thinking about another 100 ft or so? Any suggestions other than beech?

The green powder is probably some kind of algal growth. If the hedge isn't growing strongly then this can form.It won't hurt the plants but you need to get the hedge growing better, so feed it and give it a mulch of something. Is it growing in shade as this can also encourage algae?

Hornbeam as an alternative.