Craig Young
Hello Mymble, Yes, if they are Leylandii you will definitely need to keep them trimmed as they grow very quickly and can get too big very easily. Also if they are not pruned regularly and get too big you can't simply cut them back hard because they will not produce new growth from old wood. Only prune them after the last frosts of the year have passed and well before the winter is set to return. I'd recommend pruning a minimum of twice yearly. (many of my clients request they're pruned much more often than that) If kept under control this shouldn't be an expensive job. Advertise in Rated People under the 'Find a Tradesman; section if you're serious about finding a gardener to work with you. Good Luck Craig Young Spruce Garden Services Edinburgh & Lothians
