Arborvitae, members of the Thuja genus, are popular evergreens known for their dense, scale-like foliage. While many species grow into towering trees, modern landscaping requires smaller, more manageable varieties for compact spaces. Understanding the true mature size of these cultivars is paramount for avoiding an overgrown plant. This article identifies the smallest and slowest-growing Thuja options available.
Understanding Arborvitae Size Categories
The size of a Thuja cultivar is often categorized by its growth rate, which can be misleading if the ultimate mature size is not considered. Horticulturalists classify conifers based on their expected growth over a ten-year period, differentiating between dwarfs and miniatures.
A plant labeled “dwarf” typically grows slowly, adding between one and six feet in height over a decade. Cultivars in this range are significantly smaller than standard species, but a six-foot plant may still be too large for a small garden bed or container.
The “miniature” category represents the smallest arborvitae, generally growing less than six inches per year, resulting in an ultimate size under three feet. This distinction is important for small-scale applications like trough gardens. Focusing on the final, mature height and width is the only reliable way to select a plant that will not outgrow its intended space.
The Smallest Arborvitae Cultivars
The quest for the smallest possible Thuja leads to specific, ultra-compact cultivars of Thuja occidentalis. These are generally globe-shaped and prized for their extremely slow growth and natural form retention.
One of the tiniest options is ‘Anna’s Magic Ball,’ which maintains a neat, spherical habit and matures to just 10 to 15 inches in height and width. This cultivar is perfect for small spaces and offers vibrant golden-yellow foliage, providing color contrast in rock gardens.
Another miniature contender is Thuja occidentalis ‘Tiny Tim,’ which typically reaches one to two feet tall and wide. Its dense, globe shape requires virtually no pruning to maintain its form, making it a favorite for foundation plantings.
The variety ‘Teddy’ is similarly compact, forming a tight, plush mound with soft, feathery, dark green foliage. This cultivar matures to approximately two feet tall and just one foot wide, making it a narrow choice.
Slightly larger, but still within the dwarf range, is ‘Danica,’ which reaches about two feet tall and wide after ten years of growth. Other popular small globes include ‘Mr. Bowling Ball’ and ‘Tater Tot,’ typically topping out around two to three feet in height and width, making them excellent choices for low borders. The ultimate mature size should always be the deciding factor for landscape planning.
Placement and Maintenance for Dwarf Varieties
The miniature size of these arborvitae makes them highly versatile for placement in specialized garden environments. They are particularly well-suited for container gardening, where their limited root systems thrive in defined spaces, or for placement in delicate rock gardens as accent plants.
Dwarf arborvitae perform best when they receive at least six hours of direct sunlight daily to maintain their dense, characteristic foliage. Insufficient light can cause the foliage to become sparse and lose its compact shape, while in hotter climates, protection from the intense afternoon sun may be beneficial to prevent scorching.
Watering is a unique concern for small Thuja, especially when grown in pots, as container soil dries out much faster than garden soil. The soil must be kept consistently moist but never waterlogged to prevent root rot, which is particularly damaging to these small evergreens.
In winter, many Thuja varieties naturally develop a bronze or reddish hue, which is a protective mechanism. Miniature forms can be vulnerable to winter burn from harsh, drying winds. A location shielded from the worst elements is beneficial, or temporary protective wrapping can be used for young plants. Because of their naturally compact shapes, these small cultivars rarely require pruning.