I have a builder's bag of chippings from a privet hedge which was chipped 4 months ago (ie isn't green anymore). Can I use this to mulch around a newly planted hornbeam hedge (just whips) or should I worry about the lack of nitrogen in the mulch ? I'd like to use the chippings 1. To suppress weeds and 2. To empty the bag which is currently where I want to put a veg bed.