Conifer Hedges are planted in trenches, dig a trench wide 50cm (20″) And 30cm deep. Loosen up the bottom of the trench as this will encourage the downward growth of the roots.
Mix the bottom Soil with some potting compost and some organic fertiliser pellets. Place the trees in the trench & space them at approx. 30cm (12"). If you have the correct spacing ( no. of trees x meters) you can start to plant them spreading out the roots and fill up with a mix of the topsoil with potting compost. Use a planting line to ensure you have a straight line to plant along.
Water well (daily) for the next 2 weeks to ensure there is sufficient moist for the roots to start building New white roots.
During first two years do not trim the Hedge with a mechanical trimmer but by hand with a sharp secateur ( that's best). Once the Hedge has reached its desired height take out the top shoot ( use a line to keep the height level for all trees). Fertilise the Hedge in spring with oragnic fertiliser pellets. During late autumn early winter give a dose of Magnesium Salt, this keeps the Hedge Healthy and green.
Trim preferable during dark and rainy weather, it has two benefits; you won't get scorched foliage and the electric trimmer runs better on wet foliage (it gets water lubrication). So good clothing and a hat to keep you dry. Never trim a conifer Hedge with short sleeves in sun as some perople are sensitive for the foliage of Conifers (red and itchy skin).
A well trimmed Hedge is wider at the bottom and smaller at the top, (triangle shaped) this helps the Hedge to get sunlight evenly on all sides of the trees.