I planted a row of Thuja plicata atrovirens, about 4 years ago, the plants I purchased were 4ft tall and looked healthy and bushy at the time. They have now grown in height to between 6 and 8ft, but they are now very spindly and thin with very little foliage. Some are so thin it hardly looks like there is any hedge at all! I have looked on the internet and they seem to have a disease that looks like Keithia blight, any new growth is soon damaged by the blight. Is this a disease they will recover from, and will they later become more bushy? or will they just get taller and remain spindly? I have not trimmed them as I wanted these to grow into large trees, as there is plenty of space for them, Is it time I cut them down and replaced them, with something else, or wait longer for them to recover? I am in mid-Wales, do they just not grow well in this area?
Any advice would be appreciated.