Thuja occidentalis 'IslPrim' / Primo™ eastern arborvitae

Thuja occidentalis 'IslPrim' Primo™ is an irregular-growing dwarf, upright selection of eastern arborvitae with firm, spire-like growth which will quickly capture and hold the eye. It grows with refined, scale-like foliage that twists and turns providing much textural interest and beauty that more closely resembles that of a Hinoki cypress (Chamaecyparis obtusa) rather than that of an arborvitae. In summer, it is a refreshing, vivid green, which eventually becomes muted bronze for the winter in colder regions. It is on the demure side, with only 2 to 4 inches (5 – 10 cm) of growth a year, so its proportions lend itself to troughs and small spaces. It responds well to judicious pruning although that is not necessary as sculptural charm and character will develop naturally without manipulation. In 10 years, with good growing conditions, expect mature plants to measure 3 feet (1 m) tall and 1.5 feet (45 cm) in wide.

This cultivar originated as a seedling sourced from a specimen of T. occidentalis 'Zmatlik', selected in 2004 by Iseli Nursery, Boring Oregon and released to the nursery trade beginning in 2017. It is one of two plants selected in 2017 for inclusion into the ACS Collectors' Conifer of the Year Program.

Thuja occidentalis 'Isilprim' Primo™ in the Jean Iseli Memorial Garden, Boring, Oregon.
Photo by Randall Smith
© Iseli Nursery


Kim Carlisle
Here's a link to my garden blog, where I recently added a post about miniature gardens. I used a 'Primo' it!...and I'll add more information soon...
Thanks for this great plant!


This plant works great in groups. The planting looks like a miniature forest but has enough presence to work in a 'regular sized' garden!