Lilacs are extremely popular spring-blooming shrubs that add color and fragrance to gardens. There are over 200 cultivars of lilacs available, ranging in color from traditional lavender to white, pink, red, blue, and even yellow. While most people think of the common lilac bush when they hear the word “lilac,” there are also lilac trees. So what exactly is the difference between a lilac bush and a lilac tree?
Page Contents
Growth Habit
The biggest difference between lilac bushes and lilac trees comes down to their growth habits. Lilac bushes grow in a rounded, multi-stemmed form, with multiple stems coming up from the base of the plant. They tend to grow wider than they do tall. The branches of lilac bushes tend to arch gracefully outward as the bush matures.
In contrast, lilac trees grow with a single trunk and a rounded, tree-like form, branching outward from the central trunk. They have an upright habit rather than the arching, fountain-like shape of lilac bushes. Lilac trees generally grow much taller than lilac bushes, some reaching heights of over 20 feet.
Pruning
The different growth habits of lilac bushes and lilac trees means they require different pruning techniques. Lilac bushes should be pruned to remove old, unproductive wood and shape the plant. The goal is remove older branches all the way to the base to encourage new growth. Heavy pruning every few years helps keep lilac bushes productive.
Lilac trees should be pruned more like other trees, with minimal removal of large branches. Only prune branches that are dead, damaged, or crossing. Avoid removing more than 30% of the tree’s branches in one season to maintain the tree’s shape. The pruning cuts should be clean and leave branch collars.
Ideal Uses
The forms of lilac bushes and trees lend themselves to different uses in the landscape. Lilac bushes make excellent standalone specimens in perennial borders or foundation plantings where their fountain shape can be shown off. They also work well in groupings and flower borders. Keep their mature size in mind when planting.
Lilac trees make nice, small accent trees thanks to their rounded forms, spring blooms, and fall color. Plant them where they have room to reach their mature size. Avoid planting lilac trees near paved surfaces, as their suckering roots can damage pavement. Lilac trees make good privacy trees or focal points in a landscape.
Lilac Bush Uses:
- Specimen plant
- Group plantings
- Flower borders
- Foundation plantings
- Hedges and screens (some cultivars)
Lilac Tree Uses:
- Accent tree
- Small focal tree
- Privacy tree
- Specimen tree
Flowering
Lilac bushes and lilac trees bloom at around the same time in spring, with color showing anywhere from late April to June depending on climate and cultivar. The length of the bloom period can vary as well, from 1-3 weeks on average. Among lilac varieties, late-bloomers tend to have the longest bloom time.
In terms of floral display, lilac bushes put on a bigger show in spring because they are covered in blooms from top to bottom. Lilac trees also bloom profusely in spring, but more of their structural branches are visible during bloom time.
Care
Fortunately, lilac bushes and trees share very similar care needs. Both require full sun exposure and well-drained soil. Fertilization is usually not needed, but a balanced fertilizer can be applied in early spring if plants look nutrient deficient. Regular watering is important when plants are young or during drought, but established plants are quite drought tolerant. Good air circulation helps discourage powdery mildew disease.
Deadheading spent lilac blooms can help encourage reblooming on some varieties. For both lilac bushes and trees, remove spent flower clusters down to a leaf set or lateral bud. In general, you should not prune lilacs immediately after flowering since this removes the buds for the next year’s bloom.
Lilac suckers, or shoots coming up from the root system, should be promptly removed to maintain a tidy appearance and prevent reversion to non-blooming types. Monitor for pests like borers, scale, and mildew and treat any issues promptly.
Size
Mature size is one of the main differences between lilac bushes and trees. The typical lilac bush grows to a rounded size of 8-15 feet tall and wide. However, compact bush lilacs are available topping out at just 3-5 feet tall.
Lilac trees grow significantly larger than lilac bushes, capable of reaching heights of 20-30 feet tall or more with nearly equal spread. Even dwarf lilac tree varieties grow larger than lilac bushes, typically 10-15 feet tall.
Typical Mature Sizes:
| Type | Height | Width |
|---|---|---|
| Lilac bush | 8-15 feet | 8-15 feet |
| Compact lilac bush | 3-5 feet | 3-5 feet |
| Lilac tree | 20-30 feet | 15-25 feet |
| Dwarf lilac tree | 10-15 feet | 8-12 feet |
Availability
Lilac bushes are widely available at nurseries, garden centers, and retail outlets that sell plants. There are many different cultivars to choose from in a range of flower colors, bloom times, sizes, and growth habits. Dwarf bush lilacs are becoming increasingly popular for small yards.
Lilac trees may be harder to locate than standard lilac bushes. However, they are gaining popularity. Specialty catalogs and online retailers offer the best selection of lilac tree cultivars. Consider ordering ahead if you want a particular variety, as stock can be limited.
Popular Varieties
While lilac bushes have more available cultivar options, there are some excellent lilac tree varieties to consider as well:
Lilac Bushes
- Syringa vulgaris – common lilac, old garden favorite, lavender flowers
- S. ‘Charles Joly’ – magenta flowers, leathery leaves
- S. ‘Miss Kim’ – dwarf variety, pale purple blooms
- S. ‘Bloomerang’ – reblooming dwarf, pink flowers
- S. ‘Palibin’ – dwarf, pinkish-lavender blooms
- S. ‘Sensation’ – single purple and white bi-color blooms
Lilac Trees
- Syringa reticulata ‘Ivory Silk’ – fragrant ivory white blooms
- S. ‘Josee’ – reblooming dwarf variety with pinkish-purple flowers
- S. ‘Declaration’ – burgundy-red flowers in upright form
- S. ‘Penda’ – single purple flowers on compact tree
- S. ‘Miss Canada’ – prolific light pink blooms on hardy tree
Differences Summary
While both offer outstanding spring color and fragrance, there are some notable differences between lilac bushes and trees:
- Lilac bushes have a multi-stemmed, fountain-like form; lilac trees have a single trunk and rounded canopy.
- Bushes grow 8-15 feet tall and wide; trees can reach 20-30+ feet tall.
- Bushes require heavier pruning to rejuvenate; trees need minimal pruning.
- Bushes work well in flower borders; trees make nice accent or specimen trees.
- Bushes offer a wider selection of cultivars and sizes.
Conclusion
Both lilac bushes and trees add beauty to the garden with their aromatic spring flowers and attractive forms. Choose lilac bushes where a full floral display over a smaller area is desired, such as in perennial borders. For a focal point or larger landscape accent, a lilac tree is a splendid choice. With proper care and pruning, either can provide many years of enjoyment.