Plants
Arborvitae
Thuja · Cupressaceae
Arborvitae has been Germany's classic hedge for decades: fast-growing, fully screening, frost-hardy and, with varieties like ‚Smaragd‘, neat in shape even without clipping. Its aromatic scent of crushed foliage is part of many childhood garden fences. Two things deserve honest mention: thuja is poisonous, and — unlike yew — it forgives no cut into old wood.
- Light
- Sunny to partially shaded; in deep shade arborvitae goes bare.
- Watering
- Regular — the shallow-rooted plant tolerates no long dry spells, not even in winter.
- Care level
- Easy
- Botanical
- Thuja
Three varieties dominate the market: ‚Smaragd‘ grows in a slim cone, stays rich green even in winter and needs hardly any clipping — but closes gaps only slowly. ‚Brabant‘ grows noticeably faster and denser but demands two cuts a year. The large-leaved Thuja plicata ‚Martin‘ is the toughest choice for harsh sites and wide hedges.
The name has history: when French sailors fell ill with scurvy in 16th-century Canada, a vitamin-C-rich bark tea of the Iroquois cured them — and the tree arrived at the French court as „arbor vitae“, tree of life. The name has nothing to do with the plant's healthiness in the garden today.
Thuja wants a sunny to partially shaded spot with moist, nutrient-rich soil. Its shallow roots make it drought-sensitive: hedges turning brown after hot summers have usually died of thirst, not disease. Water during dry spells — including in winter when the ground is frost-free — especially in the first years.
For pruning, the iron rule of the cypress family applies: cut only into leafy, green wood. Bare brown holes never fill in again. Ideal are a light cut in late June and a second in late summer if needed — always checking for nesting birds first, as thuja hedges are popular nesting sites.
Clarity is owed on toxicity: the essential oil thujone in shoot tips and cones is poisonous to people and animals — ingestion causes gastrointestinal upset, and larger amounts can trigger cramps and liver and kidney damage. The sap can also irritate skin, which is why we recommend gloves when trimming. Clippings must be kept from grazing animals.
In floristry, thuja greenery is a winter classic: for Advent wreaths, grave arrangements and the November grave covering it has served generations thanks to its keeping quality and aromatic scent — good craftsman's material, as long as it is not used within reach of nibbling animals.
Is Arborvitae toxic to children and pets?
- Children
- Toxic
- Cats
- Toxic
- Dogs
- Toxic
The shoot tips and cones contain the essential oil thujone and are toxic to cats, dogs, horses and people; skin contact with the sap can also irritate. The cones are especially tempting for children. Dispose of clippings safely and contact poison control or a vet if ingested.
Typical symptoms: Drooling, vomiting, diarrhoea and abdominal pain; larger amounts may cause cramps and liver and kidney damage.
In an emergency:call the German poison control centre in Bonn on +49 228 19240 (24/7) — for pets, contact an emergency vet directly. This information does not replace medical or veterinary advice.
Overview: toxic & non-toxic plants for cats, dogs and children
Care
- 01Choose a sunny to partially shaded spot with moist, nutrient-rich soil.
- 02Never let it dry out: water deeply and regularly in dry spells and in the first year.
- 03Cut into green wood only — bare patches never regrow.
- 04Main cut in late June, a second in late summer if needed; check for nests first.
- 05Feed with organic fertiliser or compost in spring; Epsom salts help with browning caused by magnesium deficiency.
- 06Wear gloves when trimming — the sap can irritate skin.
Frequently asked
- Why is my thuja hedge turning brown?
- The most common cause is simply lack of water — as a shallow-rooter, thuja dies of thirst in hot summers and dry winters. Road salt, magnesium deficiency (Epsom salts help), fungal diseases or bark beetles are other candidates. A slight winter bronzing in varieties like ‚Brabant‘, however, is normal and grows out in spring.
- Is arborvitae toxic to dogs and cats?
- Yes: the thujone it contains irritates the stomach and gut and can cause cramps and organ damage in larger amounts. The bitter taste usually prevents major ingestion, but playing dogs and nibbling cats are at risk. Clear away hedge clippings immediately and see a vet if symptoms appear.
- Smaragd or Brabant — which thuja should I plant?
- ‚Smaragd‘ for anyone who wants minimal clipping: slim, winter-green, slower. ‚Brabant‘ for anyone who needs a dense hedge fast and does not mind two cuts a year. In harsh or windy sites the large-leaved Thuja plicata ‚Martin‘ is the toughest choice.
- Can a bare thuja hedge become dense again?
- Unfortunately only to a degree: thuja does not resprout from old, brown wood — bare inner sections stay bare. You can weave in neighbouring green shoots horizontally to mask gaps; with badly bared hedges, replanting is usually the more honest solution. Hence: clip regularly and lightly from the start.