A steady narrow column
The conical crown remains restrained in width and gains height without spreading untidily.
Thuja 'Smaragd' 13cm — Care & Tips
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Curves? No. Corners? None. Just one clean silhouette. 😌
Family: Cupressaceae · Pot diameter: 13cm · Height: approx. 40cm
Thuja occidentalis ‘Smaragd’ gives a space a clean vertical line that appears precisely drawn. Its narrow symmetrical crown is clothed in dense emerald-green sprays and retains colour remarkably well through winter. At an entrance, in a repeated row or as a calm evergreen background, it creates instant architectural elegance and gives the planting a timeless, polished appearance.
Young tips emerge a brighter green and gradually thicken the column, while small brown cones remain discreet. Its naturally conical habit is formal enough for structured design, yet the fine texture keeps it lively rather than rigid.
Thuja occidentalis ‘Smaragd’ holds a current RHS Award of Garden Merit, awarded in 1993.
Narrow proportions, dense upright sprays and winter green make Thuja occidentalis ‘Smaragd’ a benchmark for clean evergreen lines.
The conical crown remains restrained in width and gains height without spreading untidily.
Glossy emerald foliage retains its winter colour better than many other arborvitae selections.
Flattened branchlets stand vertically and fill the outline in many layers.
Why you will love it: it creates the long, calm green line an entrance or screen needs, without a bulky crown.
Use at an entrance, in a narrow evergreen screen or as repeated columns, in sun to light shade. Space roughly 80–100cm centre to centre for a screen, or 1.2–1.5m for distinct specimens.
The formal vertical line balances beautifully with low tufts, soft curves and seasonal flowers at its feet.
Sun to light shade; good light keeps the conical column dense from base to tip.
Water deeply during establishment and hot spells; even moisture helps prevent the base from becoming bare.
Very cold hardy, RHS H7; hot drying wind and prolonged drought can dull the foliage.
Harmful if eaten and a potential skin allergen; wear gloves when trimming and keep it away from children or animals that may chew it.
Sun to light shade; good light keeps the conical column dense from base to tip.
Water deeply during establishment and hot spells; even moisture helps prevent the base from becoming bare.
Moist but well-drained, moderately fertile soil; avoid both standing water and abrupt drying.
A light spring feed is enough; excessive feeding produces soft growth and loosens the narrow outline.
Very cold hardy, RHS H7; hot drying wind and prolonged drought can dull the foliage.
Remove only dry tips and shoots that break the column; do not cut deeply into bare old wood. Avoid removing the central leader unless you are intentionally limiting the final height.
Harmful if eaten and a potential skin allergen; wear gloves when trimming and keep it away from children or animals that may chew it.
Browning inside the crown is often normal renewal; dry tips or thinning at the base call for a check of watering, wind and competition.
The young central stem organises the first upright lateral sprays.
Each season adds new layers without a large increase in width.
The symmetrical conical crown retains a clear tip and dense base.
At maturity, Thuja occidentalis ‘Smaragd’ forms a narrow, symmetrical conical column with persistent emerald-green foliage. It supplies privacy and vertical rhythm where a broad evergreen crown would take too much room.
The two studies show how the central leader and short lateral sprays build the narrow column.
What to expect after planting: The central axis continues upwards while lateral sprays fill the column from the base. Its final narrow line becomes clearer each year, provided the leading tip remains intact.
Around 1950, at the D. T. Poulsen nursery in Kvistgård, Denmark, a distinct shoot was found on the older Thuja occidentalis ‘Kelleriis Viridis’. This natural branch sport stood out for its narrow, regular conical habit, upright growth and glossy green foliage that retained its colour through winter. It was selected as a new cultivar under the name Thuja occidentalis ‘Smaragd’.
As it spread beyond Denmark, it acquired different market names. Pépinières Minier introduced it to France in 1963 as ‘Emeraude’, while in North America it became widely known as Emerald Green. Its accepted cultivar name remains ‘Smaragd’.
In 1993, the Royal Horticultural Society granted it the Award of Garden Merit, which it still holds.
Near-vertical flattened sprays stack many foliage surfaces without rapidly broadening the crown.
A dominant central axis adds height while short lateral sprays fill the base and preserve the narrow conical outline.
Six specific answers covering position, water, soil, space and correct seasonal care.
Sun to light shade; good light keeps the conical column dense from base to tip.
Water deeply during establishment and hot spells; even moisture helps prevent the base from becoming bare.
Moist but well-drained, moderately fertile soil; avoid both standing water and abrupt drying.
An established plant commonly reaches about 3–5m high and 1–1.5m across, with natural variation between sites.
Yes. Thuja occidentalis ‘Smaragd’ usually retains a clearer green than many other arborvitae, provided it is not stressed by drought or drying wind.
Roughly 80–100cm between centres creates a continuous narrow line with room for healthy growth.