Planting A Bare Root Hedge- Spacing

Question

Hi guys I would really appreciate some expert advice. I am planting a bare root Italian alder hedge. 7 whips per metre in two staggered rows ie a row of 4 and then a row of 3. The hedge is going to be planted next to a wooden sleeper retaining wall.i would like to keep the hedge as narrow as possible.
Q1. How far from the sleeper wall can I plant row 1.
Q2. In row 1 the whips are 33cm apart. Row 2 is staggered with row 1. But how close can I plant the second row to row 1 please?
Thanks in advance!!

Answer 1

My research showed 40 to 50 cm between rows. Also, I read that Italian alder roots are invasive and should be planted 30 meters from structures.

Here's more info that may be helpful:
https://hortnews.extension.iastate.edu/2002/3-22-2002/hedges.html