The term “small tree” is imprecise in horticulture, often confusing gardeners selecting plants. Classification depends not just on final height but also on genetic programming and structural form. Understanding the terminology differentiates naturally small plants from those kept small through intervention, which is important for predicting maintenance needs and mature size.
Terminology for Naturally Small Trees
When a tree is inherently small, it is assigned a classification that reflects its genetic potential. The most common term is “dwarf,” which describes a cultivar significantly smaller than the standard species, typically reaching only 30 to 60 percent of the height of its counterpart. For instance, a standard apple tree might reach 30 feet, while a dwarf variety of the same tree may mature at 6 to 12 feet tall.
The term “miniature,” or “genetic dwarf,” refers to trees whose small stature is not due to grafting or pruning, but is their natural growth habit. These varieties are often the smallest, sometimes staying under 8 feet, and require very little pruning to maintain their compact size. They are particularly popular for container gardening because their root systems are less vigorous than those of other types.
“Semi-dwarf” trees represent an intermediate size, achieving about 60 to 90 percent of the standard tree’s mature height. These trees typically grow larger than true dwarf types, often reaching 10 to 16 feet tall at maturity. Horticulturists use these precise size classifications to guide planting decisions, as they indicate the plant’s maximum expected size.
Structural Differences Defining a Tree Versus a Shrub
The difference between a small tree and a large shrub is primarily a matter of structure rather than final size. A tree is defined by its single, dominant, woody trunk, known as a bole, which supports a distinct crown of branches well above the ground. While mature height varies by species, a tree is generally considered a woody plant with a single trunk that will exceed 13 to 20 feet in height.
A shrub, by contrast, is characterized by its multi-stemmed habit, with several woody stems branching out from the base. Shrubs typically lack the single, defined trunk of a tree and usually remain shorter than 13 feet. The structure of the plant determines its classification, not its height, which is why a very tall, multi-stemmed lilac is still considered a shrub.
This structural distinction creates a gray area for some popular landscaping plants, such as Japanese maples, which can naturally grow as multi-stemmed shrubs or be selectively trained into single-trunk small trees. In these cases, the plant’s designation depends on whether it was cultivated to feature a single, dominant stem or allowed to retain its natural cluster of stems.
Manipulation Techniques that Create Small Trees
Not all small trees are naturally small; many are standard varieties whose size is restricted through human intervention. One of the most common methods, especially in fruit production, is the use of dwarfing rootstock. This technique involves grafting the desired fruit-producing variety onto the root system of a different plant that inherently limits the growth of the canopy.
The rootstock controls the overall vigor and size of the tree above the graft union, resulting in a physically smaller plant, such as a 10-foot apple tree that would otherwise grow to 30 feet. Another technique involves intensive pruning and training, such as espalier, where a tree is trained to grow flat against a wall or trellis. This method restricts the tree’s volume and directs its energy into fruiting rather than vertical growth.
Other techniques include container growing, where the size of the container restricts the root system and the plant’s overall size. Bonsai is an extreme example of this restriction, combining precise root pruning and branch training to create a miniature tree that is genetically capable of growing much larger. These methods allow gardeners to control the mature size of a plant that is not naturally a dwarf variety.