Is there such a thing as a lilac tree?

Lilacs are beautiful spring-blooming shrubs that produce an abundance of fragrant flowers in shades of purple, pink, white, and red. They are extremely popular landscape plants because of their stunning floral display and sweet scent. But is there actually such a thing as a lilac tree? The answer is yes and no – it depends on how you define “tree.”

In the traditional sense, lilacs are not considered trees because they have multiple stems and shrub-like growth. However, there are a few different varieties of lilac that can grow into tree-like forms under the right conditions. So while lilacs are technically classified as shrubs, some unique cultivars exhibit tree-like characteristics.

Tree Lilacs

There are a handful of lilac varieties that have an upright, single-stemmed form and can grow over 15 feet tall. These lilacs take on the appearance of small flowering trees. Some examples include:

Japanese Tree Lilac

The Japanese tree lilac (Syringa reticulata) is the most commonly recognized tree form. It has a straight, upright shape that resembles a small cherry tree. It grows 15-25 feet tall with a 10-15 foot spread. The flowers are creamy white and bloom in late spring.

Peking Lilac

The Peking lilac (Syringa pekinensis) also grows in a small, rounded tree form up to 20 feet tall and wide. It features fragrant white flowers in late spring. This variety originates from Beijing, China.

Preston Lilac

The Preston lilac (Syringa x prestoniae) is a hybrid that combines traits of Japanese and Peking lilacs. It has a narrowly upright shape and grows 15-20 feet high. Its flowers are light pink and bloom in late spring.

Miss Kim Lilac

Miss Kim lilac (Syringa patula) is a dwarf, compact cultivar that matures at 6-10 feet tall. When pruned properly, it can take on a miniature tree shape. It produces pale lilac-purple blooms.

How Tree Lilacs Are Created

These upright lilac varieties occur naturally as genetic mutations. They are propagated from cuttings to maintain their tree-like shape and height. Here are some key factors that enable them to grow into tree forms:

• A dominant central leader – This allows the plant to grow vertically into a tree shape rather than bush out.
• Minimal suckering – Most lilacs produce suckers from the base, which results in a shrubby form. Tree lilacs sucker less vigorously.
• Thicker stems – Upright tree lilacs often have stouter stems than ordinary lilac shrubs.
• Pruning – Regular pruning, especially in the first few years, promotes a tree shape by removing lower side branches.

With proper pruning and care, these tree lilacs can maintain their form for many years. Periodic thinning is necessary to keep lower branches in check and sustain the tree silhouette.

Growing Conditions

Tree lilacs perform best in full sun and well-drained soil. Here are some tips for successfully growing them:

• Plant in spring once the threat of frost has passed.
• Space at least 10-15 feet apart to allow for mature size.
• Provide at least 6 hours of direct sun daily.
• Prune frequently while young to establish shape.
• Water 1-2 times per week until established.
• Fertilize in early spring with a balanced fertilizer.
• Watch for suckers and prune them out to maintain tree form.

With the right care, tree lilacs require minimal maintenance other than annual pruning. They are resistant to pests and tolerate pollution well.

Blooms and Fragrance

One of the best qualities of tree lilacs is their incredibly fragrant blooms. While the colors are generally white to light pink, they emit a stronger scent than ordinary lilac shrubs. The flowers appear in late spring on the tips of branches. Blooms last about 2-3 weeks before fading. Deadheading spent blooms can encourage potential reblooming.

Here’s a quick comparison of the bloom traits:

Variety	Flower Color	Fragrance	Bloom Time
Japanese Tree Lilac	Creamy white	Very fragrant	Late spring
Peking Lilac	White	Very fragrant	Late spring
Preston Lilac	Light pink	Very fragrant	Late spring
Miss Kim Lilac	Pale purple	Moderately fragrant	Late spring

As you can see, the flowers of tree lilacs tend to be white or light in color but their real appeal lies in their intense fragrance.

Pruning

Pruning is essential for developing and maintaining the tree form of lilacs. Here are some tips:

• Prune frequently in the first 2-3 years after planting to establish the central leader and remove lower branches.
• Remove suckers as soon as they appear to discourage shrubby growth.
• In later years, prune in late winter or early spring before new growth begins.
• Remove around 20% of the oldest branches at the base to encourage new growth.
• Maintain an open silhouette by thinning congested branches.
• Deadhead spent blooms to encourage potential reblooming.

Here is a simple annual pruning regimen to follow:

1. Prune out all dead, damaged, or diseased branches.
2. Remove suckers and waterspouts.
3. Selectively thin overcrowded branches.
4. Cut back the oldest branches at the base by about 20%.
5. Shape and trim branches to balance the canopy.

Proper pruning not only creates an attractive tree shape, but it also revitalizes lilacs by allowing more air circulation and light penetration in the canopy. This results in more prolific blooms.

Advantages of Tree Lilacs

There are many reasons why tree lilacs make exceptional landscape plants:

• They take up less space than a lilac hedge or shrub border.
• Their tree shape creates a stunning specimen plant.
• They are low maintenance when properly trained.
• Fragrant blooms are produced on compact framed branches.
• Thrives in urban settings and withstands pollution.
• Provides vertical interest in the garden.
• Grows well in colder climates.
• Has no serious pest or disease problems.

For gardens with limited space, tree lilacs are an excellent choice. Their vertically oriented shape saves room while still allowing you to enjoy breathtaking lilac blooms. The cultivars that grow 8-15 feet tall can fit into all but the smallest landscape.

Disadvantages of Tree Lilacs

Despite their merits, tree lilacs do have some disadvantages:

• Require diligent pruning, especially when young.
• Selection is limited to just a few cultivars.
• Bloom time is short, only 2-3 weeks.
• Need full sun to bloom well.
• Limited availability; may be hard to find.
• Slow growing compared to shrub lilacs.

The main drawback is that they require careful training and pruning to achieve and keep the tree form – otherwise, they will revert to a shrubby habit. Their blooming period is quite short as well. Tree lilacs also tend to be slower growing than old-fashioned lilac shrubs.

Alternatives to Tree Lilacs

If you like the look of tree lilacs but want something lower maintenance, here are a couple alternatives to consider:

Japanese Tree Lilac Alternatives

• Crape myrtle – Has exfoliating bark and summer blooms.
• Flowering cherry – Pretty spring blooms and fall foliage.
• Redbud – Blooms magenta flowers before leaves emerge.
• Serviceberry – White spring flowers and edible fruit.

These small flowering trees provide vertical interest without intensive pruning. Their drawback is they lack fragrant blooms.

Dwarf Lilac Alternatives

For a compact, tree-shaped shrub, consider:

• Dwarf Korean lilac – Grows 6 feet tall; lavender blooms.
• Bloomerang lilac – Reblooming; grows 5-7 feet tall.
• Dwarf Chinese lilac – Grows 4 feet tall; fragrant white blooms.
• Miss Canada lilac – Compact 4-5 foot shrub with pink blooms.

These dwarf lilac shrubs require less pruning to maintain a tidy shape. They repeat bloom longer than tree lilacs but have less intense fragrance.

The Best Uses for Tree Lilacs in Landscaping

Here are some ideal ways to showcase tree lilacs in the garden:

• Specimen planting – Feature one as a focal point in the yard.
• Flanking an entryway – Line the walkway or frame the front door.
• Grouped planting – Plant 3-5 in a cluster for a breathtaking spring display.
• Ornamental border – Blend with lower shrubs and perennials.
• Cut flower – Bloom sprays can be cut to enjoy indoors.
• Park and public area planting – Withstands urban conditions well.

Choose a prominent spot to show off their gorgeous blooms and form. Avoid tucking tree lilacs in the back of garden beds where they won’t be appreciated. Give them room to reach their mature size.

Conclusion

While lilacs are almost always considered a shrub, there are some unique lilac varieties that can be grown into small tree forms. Japanese tree lilac is the classic example, taking on an upright, cherry tree-like shape and growing up to 25 feet tall yet still producing the signature fragrant lilac blooms. With diligent pruning and care, especially when young, certain lilac cultivars can be trained into miniature flowering trees. Though relatively slow growing and particular about pruning, tree lilacs offer vertical interest and phenomenal spring flowers for small space gardens. If you have the patience required to shape and maintain one, it’s well worth growing a tree lilac. Just be sure you have room to accommodate its mature size without too much encroachment.