as a rule early autumn before the soil cools down or early spring when the soil starts to warm up.

Deciduous hedges mainly after leaf-fall especially if they are bare rooted. Conifers, hollies and laurels in the early spring. Many hedge plants do come in containers at a price, can be planted any time from October to March.

The tree nursery where I get my bare root hedging plants and trees says to plant between November and March. I've find they run out of some things by Feb / March so I order and plant earlier.

Hawthorn, hazel, spindle, blackthorn, hornbeam from early Nov when the plants come in to wholesalers, right up until March (they will even survive if planted after that. However, beech, a favourite, often struggles if planted late, and I always plant it before Christmas so that it has a chance to make some root before it breaks into leaf. (Did I mention the C word? Sorry). Phil J