Sweet Gum ‘Slender Silhouette’ – By Steve Huddleston

Steve’s first meeting with ‘Slender Silhouette’ sweet gum at the German garden show in 2018.

I first saw this cultivar of sweet gum at a garden show in Germany in 2018, only to find out later that a nurseryman from Franklin County, Tennessee, discovered it growing wild in his neck of the woods. Don Shadow or Shadow Wholesale Nursery, a fourth-generation nurseryman known for introducing great plants to the trade, found it growing along railroad tracks near his nursery.

The columnar habit of ‘Slender Silhouette’ is really visible here at the Fort Worth Botanic Gardens. Click image for larger view.

‘Slender Silhouette’ is a tall, columnar cultivar of sweet gum, the familiar native tree of East Texas and the Gulf South. This cultivar will grow 50 to 60 ft. tall and only 5 to 6 ft. wide. As it matures, it maintains its columnar form and is just as wide at the top as it is at the bottom.

Its leaves are 5-pointed and deep, lustrous green all summer. Fall color is brilliant in orange, yellow and burgundy.

The tree’s bark is dark brown or gray and becomes deeply furrowed as the tree matures. The deciduous leaves are dark green, glossy, and star-shaped with five points. They are fragrant when bruised. Fall colors include the yellows, oranges, and burgundies for which the species is known.

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The tree produces inconspicuous, yellow-green flowers in the spring. However, these flowers yield very conspicuous fruit. The fruit are round, brown, spiky, woody capsules less than an inch wide. They can be a pain to step on with bare feet. However, ‘Slender Silhouette’ produces fewer fruit than the species, which means there will be less mess on the ground when the fruit drop in the fall.

As with the species, ‘Slender Silhouette’ prefers acidic soil (pH 6.0 or lower), but it will do well in neutral soils (pH 7.0). The leaves can suffer from chlorosis (yellowing) in alkaline soils. It’s best when the soils are deep, moist, and well drained.

It’s preferable to plant ‘Slender Silhouette’ in rather poor soils to yield slower growth and to maintain its narrow growth habit. If it’s planted in ideal conditions, the tree may grow too quickly and splay open.

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Plant ‘Slender Silhouette’ in full sun to partial shade (4 hours of direct sun or more). Be sure you have the tree perfectly plumb at the time of planting. Mulch it well to retain moisture and to moderate soil temperature extremes, but do not pile mulch up around the trunk.

‘Slender Silhouette’ is especially useful in narrow spaces between houses, along drives, in medians and parkways and in smaller gardens.

When you need a vertical look, ‘Slender Silhouette’ might be a good choice. Click image for larger view.

What you’ll want to know…
Botanical name: Liquidambar styraciflua ‘Slender Silhouette.’ The genus name originates from the Latin words liquidus, meaning “liquid,” and ambar, meaning “amber.” This refers to the tree’s aromatic resin, or gum, that exudes from a wound to the tree.
Belongs to the family Altingiaceae.
Hardy in Zones 5-9.
Resistant to deer and rabbits and tolerant of dry soil (after establishment), clay soil, and urban conditions.
Use as an accent, barrier, border, screen, or street tree.

Note: This cultivar may not be widely available yet in the retail nursery trade, but your independent retail garden center or landscape contractor can probably order it for you, especially when they begin to bring in their deliveries this fall or early next spring. Ask, and be willing to wait.

Posted by Steve Huddleston
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