Thuja occidentalis 'Smaragd' – Emerald Green Arborvitae
Thuja occidentalis 'Smaragd' is a refined, slow-growing evergreen conifer prized above all for the exceptional, jewel-bright emerald green of its foliage — a colour it holds with remarkable consistency through every season of the year, including the depths of winter when many conifers turn dull or bronze. Its naturally slender, pencil-like silhouette and dense, finely textured sprays make it one of the most elegant and versatile conifers available, equally at home as a formal clipped hedge, a structural specimen, or a neat accent in a mixed planting scheme.
Where 'Smaragd' truly distinguishes itself is in its combination of ornamental quality and ease of management. Its naturally compact, well-ordered habit requires very little intervention to look its best, and its moderate, controlled growth rate means it stays in proportion far longer than faster-growing alternatives. For gardeners seeking a conifer that is genuinely beautiful, reliably tidy, and straightforward to care for, 'Smaragd' is an outstanding choice.
Habit & Appearance
Form and foliage. 'Smaragd' produces a strongly upright, narrowly conical form that is naturally neat and symmetrical from an early age. The foliage is arranged in flat, overlapping sprays of fine, scale-like leaves with a smooth, slightly glossy surface and a pleasant, resinous fragrance when brushed or trimmed. The defining characteristic of this cultivar is its foliage colour — a vivid, saturated emerald green that genuinely earns its name and, crucially, does not fade, bronze, or yellow through autumn and winter as many Thuja cultivars can. New spring growth emerges in a fresh, slightly brighter green before settling into the rich, deep tone that makes 'Smaragd' so instantly recognisable. Left to develop naturally, plants form a slender, elegant spire that gives the garden strong vertical structure and year-round interest.
Growth rate. Unlike some hedging conifers, 'Smaragd' is a moderate rather than vigorous grower, typically putting on around 15–25 cm per year under good conditions. This measured pace is one of its great virtues — it means the plant stays manageable, retains its proportions naturally, and rarely demands the frequent, heavy trimming that faster-growing alternatives require. For those who want a tidy, well-behaved conifer that rewards patience with enduring beauty, the growth rate is an advantage rather than a limitation.
Growing Conditions
Position. Thuja 'Smaragd' performs best in a position receiving full sun to light partial shade. A bright, open aspect will produce the densest foliage and the most vivid colouring, though the plant tolerates dappled shade reasonably well. It is fully hardy throughout the UK and copes well with exposed, windy sites, making it a reliable choice for more challenging garden positions as well as sheltered, formal settings.
Soil. 'Smaragd' is adaptable to a broad range of well-drained soils, including loam, clay, and sandy ground, provided they are not prone to waterlogging. Like most Thuja, it will not perform well in permanently wet or poorly drained conditions — if planting on heavy ground, improving drainage and incorporating organic matter at planting will give the best results. A slightly acid to neutral soil pH is ideal, though it will tolerate mildly alkaline conditions without significant difficulty.
Planting spacing. For a formal, close-clipped hedge, spacing plants approximately 40–60 cm apart will produce a dense, uniform line. For more relaxed or informal planting, or where individual specimens are intended to display their natural conical shape, wider spacing or solitary planting is perfectly appropriate. As a specimen or accent plant, 'Smaragd' works beautifully in pairs flanking an entrance or repeated at intervals to create rhythm in a border.
Care
Watering. Water regularly and thoroughly throughout the first growing season after planting to support good root establishment. This is especially important during dry spells in spring and summer, when newly planted conifers are most vulnerable. Once well established, 'Smaragd' becomes reasonably drought tolerant and will generally need supplementary watering only during prolonged dry periods.
Feeding. Apply a balanced, slow-release granular fertiliser — ideally one formulated for conifers or hedging plants — in early spring each year to encourage healthy, consistent growth and strong foliage colour. A mulch of bark chippings or garden compost applied around the base in spring will help conserve soil moisture, suppress competing weeds, and protect the root zone from temperature fluctuations.
Pruning. One of 'Smaragd's' most appealing qualities is its naturally disciplined form, which often requires very little trimming at all when grown as a specimen. For hedging or where a particularly precise, formal outline is desired, a single light trim once a year — ideally in late spring or early summer after the main flush of new growth — is generally all that is needed to keep plants looking crisp and well-defined. A second, lighter pass in late summer can be given if required. As with all Thuja, avoid cutting back hard into old, bare wood, as the plant will not regenerate from stems that have lost their foliage. Regular, gentle trimming carried out from an early stage consistently delivers the neatest and most attractive results.
Ideal Uses
Formal hedging – Narrow habit and dense foliage clip to a crisp, elegant hedge line with minimal effort.
Specimen and accent planting – The slender, jewel-green spire creates a striking vertical accent in borders, courtyards, and open lawn settings.
Entrance framing – Planted in matching pairs,
