Sweet gum

Tree

Liquidambar styraciflua

Sweet gum

Tall, conical tree with star-shaped leaves that blaze red, orange and purple for weeks in autumn.

  • Full sun, Partial shade
  • 15–25 m (49–82 ft)
  • 8–12 m (26–39 ft)
  • H6 · Zone 6
  • Deciduous

Overview

Sweet gum is a large deciduous tree from the eastern United States and Mexico. Its glossy, star-shaped leaves turn shades of crimson, orange, purple and gold in autumn and hang on for weeks, and spiky round seed balls follow. Older bark becomes corky and ridged.

It is hardy to about −20°C (−4°F), USDA zones 5–9, and in gardens grows to 15–25 m (50–80 ft), taller in the wild. It needs neutral to acid soil; on chalk the leaves turn yellow. It copes with heat and humid summers and colours best in full sun.

The shallow roots and falling seed balls make it unsuitable near paving.

At a Glance

Sun Full sun, Partial shade
Height 15–25 m (49–82 ft)
Spread 8–12 m (26–39 ft)
Hardiness H6 · Zone 6
Soil Clay, Loam, Sand
Moisture Moist well drained
Habit Upright
Water Moderate
Maintenance Easy

Growing Conditions

Min. Temperature -20°C (-4°F)
pH Range 5–7
Fertility Average
Drainage Moderate

Aspect Suitability

  • East-facing
  • South-facing
  • West-facing

Site Tolerance

  • Exposed sites

Soil Tolerance

  • Clay
  • Sandy
  • Loam
  • Acid
  • Neutral pH

Foliage

Persistence Deciduous
Colour Green, Red, Purple, Orange
Leaf shape / texture Star-shaped, maple-like
  • Autumn colour

Foliage interest: April–November

Seasonal Timeline

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Foliage
Fruiting
Propagate
  • Foliage Apr May Jun Jul Aug Sep Oct Nov
  • Fruiting Sep Oct Nov Dec
  • Propagate Mar Jul Aug

How to propagate

Ways to grow more Sweet gum: the usual steps for each method.

From seed Mar Easy

You'll need: Seed compost, a seed tray or small pots, labels, and a clear lid or plastic bag.

  1. Fill a tray or pots with seed compost, level it and firm it gently.
  2. Water the compost and let it drain.
  3. Sow the seeds thinly on top. Cover them with a fine layer of compost or vermiculite about as deep as the seed is big; leave tiny seeds uncovered.
  4. Label them, cover with a clear lid or bag, and keep them somewhere bright but out of hot sun.
  5. Keep the compost just moist, and take the cover off once seedlings appear.
How long
Usually comes up in 1 to 3 weeks.
It's worked when
Seedlings with their first pair of leaves.
Then
When each has its first true leaves, prick them out into their own small pots, holding them by a leaf, never the stem. Harden them off for a week or two before planting out.
Semi-ripe cuttings Jul–Aug Takes a little care

You'll need: Clean, sharp secateurs, small pots, gritty compost, and rooting powder if you have it.

  1. Choose this year's shoots that are firm at the base but still soft at the tip, and cut pieces 10 to 15 cm long.
  2. Trim just below a leaf joint and take off the lower leaves; pinch out the soft tip.
  3. Dip the cut end in rooting powder if you have some.
  4. Push them into pots of gritty compost, water them in and cover with a clear bag.
  5. Keep them in a cold frame, greenhouse or bright windowsill out of direct sun.
How long
Roots in about 6 to 10 weeks.
It's worked when
New leaves, and the cutting resists when you tug it gently.
Then
Keep them somewhere cool and frost-free over winter, and pot them up separately in spring.

Seed needs a cold spell before sowing; cuttings root with bottom heat.

Garden Design

Works well in: Modern / Contemporary, Woodland / Shade

A large lawn or avenue tree for long-lasting autumn colour; fallen seed balls are a nuisance on paths.

Companion planting: Bulbs, Ferns

Wildlife Value

  • Moths
  • Birds
  • Shelter
  • Food source
  • Caterpillar food plant
  • Nesting cover for birds
  • Food

Food for birds: January, February, November, December