Syringa reticulata and S. pekinensis
The large and fragrant flower of the common lilac is a fondly held memory and experience for many of us. Most often planted as a shrub, lilacs have also been grown in tree form for some time. However, they are not used as often as they should as a tree. In addition to the more familiar shrub forms, there are tree forms of this plant. As we get better at selecting small maturing trees for use in smaller spaces, tree lilacs Syringa reticulata and S. pekinensis are definitely ones to consider.
Tree lilacs are relatively small, at most about 20 to 30 feet tall and 15 to 25 feet wide. Leaves are opposite, single, entire, broad-ovate, 2 to 5 and half inches long and about half as wide. Leaves are dark green on top and grayish green and reticulate (netlike pattern) on the bottom. The undersides might also be glabrous or slightly pubescent. Spring growth appears to be fresh, clean and balanced. Newly emerging leaves have a wine colored hue, turning green as they expand. Bloom time is early summer. Flowers are white to cream color, born on stalks 6 to 12inches tall and 5 to 8inches wide. I have found them to be fragrant and agreeable while Dirr has noted some smell privet-like, un-appealing to some.
Trunks are for the most part very straight with prefect branch structure at almost a 90 degree angle of attachment before curving upward to form an ascending crown. Twigs and limbs are a bit brittle, somewhat of a concern for shipping or when children like to reach out and grab a limb. A little corrective pruning is beneficial as they age but otherwise are relatively care free trees.
Generally, lilacs can be susceptible to disease and frost injury but the selections are found to be more resistant. Transplanting is relatively easy and they favor loose, well drained soils that are slightly acid, although they are known to be tolerant of a wide pH range. They grow best in full sun and will take some shade. They have good drought tolerance once established, important to consider as our climate changes
Fortunately, more and improved varieties continue to reach the market. One of the oldest and well known selections is Syringa reticulata ‘Ivory Silk’ introduced in 1973. Others are ‘China Girl’ and ‘Summer Snow’ to name a few. Another closely related tree is Syringa pekinensis ‘Summer Charm’. Make a point of requesting these for small planting space locations and you might find them more available.