welcome to GoY Sonj
https://www.rhs.org.uk/Plants/89917/Thuja-plicata-Zebrina-(v)/Details

gives some back ground.

how tall are they?

Are you 100% they're Thuja? Because these trees do not regrow from woody parts such as the trunk - growth buds are present on any green areas such as tips of branches and along the branch, but not hard, non green woody parts. That means, if you cut them right down, you won't get growth from the centre, only off any green branches left below that point. They may produce enough growth to cover up the bare centres over time, if the new growth grows upwards and not sideways, but there will always be a cut off trunk in the middle of each tree.

You won’t destroy them by coming down several feet, done carefully you can conceal the cut by cutting it down a little into the top foliage, thuja can be cut back to hard wood, and will respond, however it can be a slow process, have renovated these on many occasions over the years from trees, shrubs and hedges, with good success, but on rare occasions they have not responded, I prefer to carry out this renovation pruning round about April time and always forwarn the client that it can be temperamental.

Hi and many thanks for all your responses!

Having done a bit more research, I think they may actually be Leylandii? Could this be right? I'm not sure how to attach photos to this thread.

I really don't want to spoilt the trees so would it be worth asking a consultant to come out? Local tree surgeons will be all too eager to cut them way back without really considering how they are going to look.

Any further ideas would be greatly appreciated!

Sonja

If they're Leyland Cypress, they can be reduced in height, but if its more than half the height you want to remove, best done in stages, by taking a third off in April and then half either the following year, or later in the same year if the tree has recovered. Info below, under Pruning Overgrown Hedges:

https://www.rhs.org.uk/advice/profile?pid=596

If you;re still not sure, then yes, I'm sure a tree surgeon will sort it out for you... It's not easy to tell these trees (Thuja or leylandii) apart either - both have tiny scale like leaves in groups of 4 round the stems, and the branchlets form flattened sprays. What is different are the cones - on leylandii, they're round and pea sized, pale beige to start with, on Thuja, they're browner, small but elongated... Otherwise, eventual height and rate of growth is a way of telling, but that's not much use to you because you don't know how fast they grew...