When to Plant and Prune Thuja and Hedges
A hedge is one of the few things in a garden that you only get to build once. Get the species, the spacing and the planting time right at the outset and the hedge will do its job for decades. Get them wrong and the mistake only shows up in the third or fourth year, by which point there is no longer any simple remedy.
When to plant
In the continental conditions of Vojvodina and Srem, autumn is the best time to plant a hedge. The window from mid-September to mid-October, while the soil is still warm from the summer but the air has already cooled, gives the plant several weeks to put out new roots without the pressure of evaporation. First frosts arrive here in the second half of October, so planting of evergreen species is not left any later than that — the roots need to take hold while the ground is still mild.
The other workable slot is early spring, from mid-March to the beginning of April, as soon as the soil has dried out enough not to stick to the spade. Spring planting calls for considerably more watering through the first season. Container-grown stock can go in even in midsummer, given reliable watering and a little shade in the first few weeks — that is not impossible, simply the most demanding option. What really must be avoided is planting into frozen or waterlogged ground in late winter, because it creates a compacted layer around the roots that is hard to put right afterwards.
Species that do well here
Thuja
Thuja occidentalis 'Smaragd' is the safest choice for a narrow, formal hedge: it grows slowly, holds its conical shape by itself and needs little pruning. Plant at 60 to 70 cm along the row. 'Brabant' grows faster and wider, goes in at 80 to 100 cm and needs two cuts a year to stop it thinning out at the base. Thuja copes poorly with drought and reflected heat, so against a south-facing wall, a concrete path or asphalt it will almost always yellow if it is not watered.
Cherry laurel
Prunus laurocerasus, most often 'Rotundifolia' or 'Novita', gives a dense, large-leaved hedge and, unlike thuja, tolerates partial shade and a northerly aspect. Spacing is 70 to 100 cm depending on the cultivar. Its great advantage is that it regenerates from old wood, so a neglected hedge can be cut back and rejuvenated. On open ground with no shelter it can suffer in hard winters, particularly where the košava — which in Srem blows from the south-east — dries the leaves out for days on end above frozen soil.
Privet
Ligustrum is the most tolerant of the three: it puts up with compacted soil, drought, frequent cutting and urban pollution. In our winters it is semi-evergreen and in colder years it ends up looking sparse, which makes it a better choice for a boundary or street hedge than for year-round screening. Plant at 40 to 50 cm, often in two staggered rows.
Pruning, and why timing matters
With thuja there is one rule that admits no exceptions: never cut back into old, bare wood. There are no dormant buds on the brown part of a branch, so any hole made there is permanent. Thuja is therefore trimmed only within the green growth, in late May or June, with a light tidy-up at the end of August if needed.
Cherry laurel should be cut with secateurs rather than a trimmer — a leaf sliced in half turns brown and the hedge looks damaged for weeks. The main cut comes after flowering, in May or June, and a second in early August; hard rejuvenation is done in March. Privet needs two or three cuts between May and the end of August.
What applies to all three: no cutting after mid-September, because the young growth has no time to harden off before the first frosts. Nor should you cut in frosty weather or in strong midday sun. The profile of the hedge should be slightly tapered, narrower at the top than at the base. If the sides are vertical or, worse still, wider at the top, the bottom third stays in shade, thins out and never fills back in.
The first year after planting
- Water infrequently but generously — once or twice a week, and down to root depth, rather than a daily surface sprinkle.
- Spread a layer of bark mulch, five to eight centimetres deep, but not right up against the stem.
- Feed in spring; after mid-August, nitrogen produces nothing but soft growth that suffers over winter.
- Water evergreens thoroughly in late autumn, before the ground freezes. Winter yellowing of thuja is usually the result of drying out rather than of cold.
The commonest mistakes
The commonest serious mistake is planting too densely. Container stock looks small, so it gets lined up at 40 cm to make the hedge "close up faster". After the fourth year the plants start shading one another, the lower branches die back, and fungal disease takes hold more easily in the crowded growth. The hedge is no denser for it — it is simply, and irreparably, thin at the base.
Other mistakes that come up again and again: planting too deep, so that the root collar disappears below the soil; leaving the circling roots of container stock unteased; planting hard against the fence, without 50 to 60 cm of clearance for the eventual spread; and a row of thuja under the roof gutter, where the water alternately drowns and parches them.
The choice of species, the spacing and the timing all depend on the soil type, the aspect and how quickly you actually need the screening. If the hedge is part of a wider scheme for the plot, our garden installation work begins with a survey of the site and a planting layout drawn up before a single plant is bought, and only then come the plan, the installation and the fine adjustment on site. What most affects the cost is the length of the row, the choice of species and the height of the stock, machinery access and the condition of the soil — all of which is resolved quickest on a free site visit, after which you receive a quote with no obligation whatsoever.