The question of whether lilacs are trees or bushes often sparks debate among gardeners and plant enthusiasts. The truth is a bit more nuanced than a simple "tree" or "bush" answer. Lilacs are, in fact, large shrubs, or multi-stemmed deciduous woody plants. While they can grow quite tall, reaching heights of up to 20 feet in some cases, they lack the single, dominant trunk that defines a tree.
Key Differences: Trees vs. Shrubs
To understand why lilacs are classified as shrubs, let's look at the key distinctions between trees and shrubs:
- Trunk: Trees typically have a single, well-defined trunk that branches out higher up. Shrubs, on the other hand, often have multiple stems arising from the base.
- Height: While size isn't the sole determining factor, trees generally grow taller than shrubs. However, some shrubs, like lilacs, can achieve considerable height.
- Branching: Tree branches tend to be more elevated and spaced apart, while shrub branches are typically more dense and closer to the ground.
- Form: Trees generally develop a more defined, upright form, while shrubs can exhibit more diverse shapes and spreading habits.
The Lilac's Growth Habit: A Closer Look
Lilacs are known for their multiple stems arising from the base, forming a dense, bushy structure. While you can train a lilac to grow with a single, dominant stem—creating a more tree-like appearance—its natural growth habit is to produce numerous stems, clearly identifying it as a shrub. The size variation you see in lilacs often depends on the cultivar and growing conditions. Some varieties are naturally more compact, while others can reach considerable heights.
Factors Affecting Lilac Size:
- Cultivar: Different lilac cultivars exhibit varying growth habits, with some remaining smaller and bushier, while others have a more upright and taller form.
- Pruning: Regular pruning plays a significant role in shaping the lilac and maintaining its size. Proper pruning techniques can encourage a more tree-like structure or keep it compact and bushy.
- Growing Conditions: Nutrient-rich soil and adequate sunlight will generally result in more vigorous growth, potentially leading to a larger lilac.
Conclusion: Lilacs are Shrubs, Not Trees
Although some lilacs can grow impressively tall, their multiple stems, dense branching, and natural bushy habit firmly place them in the shrub category. While you might find a lilac that resembles a small tree in size, its fundamental structure will always remain characteristically shrub-like. Understanding this distinction is crucial for proper planting, pruning, and overall care of your lilac.
