Slender Silhouette sweetgum

Sun

Full sun gives the best shape and autumn colour; tolerates light partial shade.

Water

Keep the root zone evenly moist while establishing. Once established, water deeply during prolonged dry spells, particularly in hot climates.

Soil

Moist, well-drained, acidic to neutral soil; tolerates clay if drainage is adequate. Avoid chalky or strongly alkaline soil, where leaves may turn yellow.

Height

40-60 ft (12-18 m)

Spread

5-8 ft (1.5-2.4 m), potentially wider with age

Foliage

Glossy green, star-shaped leaves with five to seven pointed lobes. Autumn colour can combine yellow, orange, red and purple; the display varies with climate and growing conditions.

Growth

Moderate to fast once established, depending on moisture, soil and summer warmth.

Care needed

Medium

• Heat tolerant
• Wildlife

Northern hemisphere months. In Australia, shift them by six.

Difficulty

Moderate

Toughness

Fairly tough

Pick your zone, country, light and whether you have pets.

1. Planting day

   7 ft (2 m)

2. After 1 year

   9 ft (2.8 m)

3. After 2 years

   12 ft (3.6 m)

4. After 3 years

   15 ft (4.4 m)

5. After 5 years

   20 ft (6.1 m)

About 16 years to full size.

From a typical nursery size, at an average rate for this kind of plant. A rule of thumb, not a forecast.

Cats and dogs

Safe

Native to

the US

Growth rate

Fast

• Plant while dormant, using a young container-grown tree where possible; established sweetgums resent root disturbance.
• Water deeply through the first two or three growing seasons, checking the soil before watering again.
• Maintain a 2-3 in (5-8 cm) layer of organic mulch over the root zone, keeping it clear of the trunk.
• Feed only if growth is poor and a soil test indicates a deficiency; avoid routine heavy nitrogen feeding.
• Stake only if the root ball moves in wind, and remove ties once the tree is secure.
• Allow space away from paving and drains; a narrow crown does not mean a narrow root system.

Pruning. Prune lightly in late winter while dormant, removing dead, damaged or crossing branches and any competing leader. Preserve the central leader and natural columnar outline; do not top the tree or routinely shear its sides.

Autumn

Plant after leaf fall where winters are mild and the soil is workable; water thoroughly.

Late winter

Check the central leader and remove damaged or competing shoots with minimal pruning.

Spring

Plant in colder regions once the soil is workable; renew mulch and check staking ties.

Late spring

Check new leaves for yellowing between green veins, which may indicate alkaline soil or root stress.

Summer

Water young trees deeply during dry weather and keep grass away from the trunk.

Late autumn

Collect fallen seed balls from paths and lawns, and compost healthy fallen leaves.

• Use as a tall vertical accent at the back of a mixed border, with lower shrubs concealing the trunk base.
• Plant a spaced row to frame a long view or mark a boundary without the broad canopy of ordinary sweetgum.
• Repeat beside a large lawn or formal garden to create a consistent upright rhythm.
• Combine with ornamental grasses and autumn-flowering perennials for contrasting shapes and seasonal colour.

Garden styles it suits: Architectural minimal, Formal, Modern, Urban city garden, Autumn colour and Grand estate.

Plant it with: Oakleaf hydrangea, Virginia sweetspire, Japanese forest grass, Switchgrass, Christmas fern and New England aster.

Wildlife: The seeds are eaten by small birds and mammals, and the crown provides shelter and nesting sites. In its native eastern North American range, sweetgum also supports caterpillars and other leaf-feeding insects; its wind-pollinated flowers are not a significant nectar source.

• Yellow leaves with green veins: alkaline soil can prevent iron uptake. Test the soil, correct drainage problems and use chelated iron suitable for the soil pH if needed; persistently chalky sites are unsuitable.
• Leaf scorch or early leaf drop: drought, heat or disturbed roots can cause browning. Water deeply, mulch and avoid digging within the root zone.
• Scale insects: inspect twigs for attached bumps and sticky honeydew. Encourage natural predators and treat significant infestations with an appropriate horticultural oil according to the label.
• Surface roots and prickly seed-ball litter: keep the tree away from paving and busy seating areas, collect fallen fruits and do not cut major roots to accommodate paths.

Sweetgum is not known to be toxic to people, cats, dogs or horses. The hard, prickly seed balls can injure bare feet or paws and can pose a choking or intestinal-obstruction risk if swallowed.

• American sweetgum (Liquidambar styraciflua)

  The ordinary species has the same star-shaped leaves and prickly seed balls but develops a much broader crown rather than this cultivar's tightly upright outline.

• Columnar Norway maple (Acer platanoides 'Columnare')

  Maple leaves and buds occur in opposite pairs, while sweetgum leaves and buds alternate along the twig. Norway maple produces paired winged seeds rather than spiky balls.

• Lombardy poplar (Populus nigra 'Italica')

  It has a similarly narrow silhouette but triangular to diamond-shaped leaves rather than star-shaped leaves, and it does not produce woody, prickly seed balls.

Liquidambar combines Latin liquidus, meaning liquid, with Arabic ambar, referring to the fragrant resin, while 'Slender Silhouette' describes the cultivar's narrow outline.

Propagation. Propagate by grafting onto Liquidambar styraciflua rootstock, usually by a specialist nursery. Seedlings do not reliably retain the cultivar's narrow shape.

Accepted botanical name

Liquidambar styraciflua

In the US and Canada

Native in the lower 48 states.

Native range

Alabama, Arkansas, Belize, Connecticut, El Salvador, Florida, Georgia, Guatemala, Honduras, Illinois, Indiana and Kentucky.

Measured

Soil pH 4.5 to 7. Average height 1840 cm.

Sources: GBIF (CC BY 4.0), USDA PLANTS and Trefle (CC BY 4.0). The care and design notes are LandscapeGPT's own.