hi i am in Ireland and may is the perfect time for us to plant out.
At the 21st of june we can have up to 21/22 hours of light by the time the light gets back to under 13.5 hours a day. leaves us with a harvest date round about late october. plenty of time but like said above just be smaller the longer ya leave it. and holands hope is a good strain if ya get wet weather near ur harvest time. they are mould resistant and hardly aswell
best of luck