Thuja standishii x plicata 'Steeplechase' / Steeplechase hybrid arborvitae
Thuja standishii×plicata'Steeplechase' is a popular and attractive dense, broadly pyramidal shrub-form of hybrid arborvitae with finely textured, rich-green foliage. It is an ideal choice for hedgerows, screens, or as as a standalone specimen. 'Steeplechase is an excellent alternative to Italian cypress (Cupressus sempervirens) in colder climates where one desires a Mediterranean style.
At maturity, a specimen will measure 20 feet (6 m) tall and 8 feet (2.5 m) wide, an annual growth rate of 2 feet (60 cm). It will quickly become a massive tree that will be hard to keep in bounds even when judiciously pruned.
This cultivar originated as a branch sport found in 1990 on a specimen of 'Green Giant' by Alan Jones of Felton, Pennsylvania, USA. It was granted U.S. Plant Patent #16094 in 2004 for broader, more finely textured foliage than it's mother plant as well a denser, bushier growth habit.
Thuja standishii × plicata 'Steeplechase' — a 1999 accession at the New York Botanical Garden, The Bronx, New York (USDA Hardiness Zone 7a); photo from 2020.
A formidable hedgerow of Thuja × 'Steeplechase.'
Photo by The Gardener Direct, LLC