Liquidambar

liquidambar

( li - kwid - AM - bar )

At-A-Glance Information

This genus, commonly known as Sweet Gum, Star Gum, Red Gum, Satin-Walnut or American Storax, is made up of species of deciduous trees that need full sun and moderate to regular water to perform well in the landscape. They will attract birds to the garden. The foliage is beautiful, turning brilliant colors in fall, and casts deep shade in summertime. Younger trees have an upright habit, while mature ones have spreading canopies. Flowers are inconspicuous. Spiky ball-shaped fruits fall from trees throughout the year. They are good street trees if given enough distance from sidewalks and roads; their root systems will raise paved surfaces. Use these trees in the landscape as shade trees, accents, background plantings, or simply to add fall color to the garden. Although these plants are not considered toxic, their spiky seed balls can be a physical hazard to grazing animals and barefoot humans.

liquidambar Species and Varietals

Liquidambar is a member of the plant family Altingiaceae, and includes 15 extant species. Plants in this genus are related to those in Fothergilla, Witch-Hazel, and Parrotia. The common name Sweet Gum refers to the sweet-smelling resin that the trees exude when damaged. The best growing zones for Sweet Gum trees vary depending on the species. For more information, see the descriptions below. To find your zone, click here: Zone Map.

Liquidambar acalycina (Chang's Sweet Gum, Chinese Sweet Gum)
Native to southern China, these trees reach between 30-50 feet tall and have a crown that spread to 20-30 feet wide. Leaves turn red in autumn before falling. Bark is brown to black in color. Flowers are insignificant and yellow-green. Hardy down to 5 degrees Fahrenheit, these trees prefer full sun to partial shade. Cultivars include 'Burgundy Flush' (with purple new leaves that mature to green and turn burgundy-red in fall) and 'Spinners' (to 3-45 feet tall with a conical habit). Chang's Sweetgum grows well in USDA hardiness zones 6-9.

Liquidambar cambodiana (Sdey)
Endemic to southwestern areas of Cambodia, this species of Sweet Gum reaches between 26 and 33 feet tall when mature. Upper sides of leaves are glossy. These trees have not been seen growing naturally in their native range for a few decades, and the species may be extinct. This species grows well in USDA hardiness zones 10-12.

Liquidambar excelsa (Altingia escelsa) (Mala, Rasamala, Xì qīng pí, 细青皮, Tulasan, Nantayok)
These trees are native to Tibet, Yunnan Province in China, the eastern Himalayas, Assam, Bangladesh, and Southeastern Asia. They can reach upwards of 200 feet tall at maturity, and are typically found growing naturally in wet tropical forested areas. Leaves are simple. This species of Liquidambar grows well in USDA hardiness zones 9-11.

Liquidambar formosana (Formosan Gum, Chinese Sweet Gum, Formosa Sweet Gum, Fēng Xiāng, 枫香, 楓香)
Best in USDA hardiness zones 7a-9b or Sunset growing zones 4-9, 14-24, and native to East Asia, these trees reach 40-60 feet tall and 25 feet wide at maturity. Forms vary depending on individual trees. Leaves are violet when new, mature to deep green, and turn red to yellow in fall. Leaves drop in early wintertime and have three lobes.

Liquidambar orientalis (Oriental Sweetgum, Turkish Sweetgum, Amber Tree, Levant Storax, Styrax Levant, Oriental Styrax, Günlük, Sığla Ağacı)
Native to floodplains in the eastern Mediterranean region, these deciduous trees reach between 98 and 115 feet tall at maturity. These attractive landscape ornamentals are valued for their colorful fall leaves and grow well in areas with mean annual temperatures around 65 degrees Fahrenheit. Bark is greyish-brown and fissured on mature trees. Oriental Sweetgum grows well in USDA hardiness zones 7-9.

Liquidambar styraciflua (American Sweet Gum, American Storax, Hazel Pie, Bilsted, Redgum, Satin-Walnut, Star-Leaved Gum, Alligatorwood, Gumball Tree)
This species of Sweet Gum is native to the eastern United States and grows well in USDA hardiness zones 5-9 or Sunset growing zones 3-9 and 14-24. It reaches around 60 feet tall in gardens, but can get much taller in larger spaces, and spreads to 20-25 feet wide. Bark is furrowed and branches have a pleasing pattern to them. Leaves are deep green in spring and summertime, and turn purple, yellow, or red in fall. This species can behave invasively in the southeastern and eastern United States.

'Burgundy'
Deep purple-red fall color, and foliage hangs on for a long time, sometimes even through winter.

'Cherokee'
Produces few seedpods; fall color is burgundy-red (yellow if in shade).

'Emerald Sentinel'
30 feet tall and 12 feet wide, with a pyramid to column shape, and yellow-orange to orange fall color.

'Festival'
Narrow, columnar tree with light green leaves and fall color that is a combination of pink, yellow, peach, and burgundy.

'Gold Dust'
45 feet tall and 30 feet wide, with green leaves flecked with yellow. Fall color is pink, yellow, and burgundy.

'Golden Treasure'
Deep green leaves are edged in gold, In fall, edges turn pale yellow, then white, and the green center turns burgundy.

'Moraine'
Very cold-tolerant species of Liquidambar, to 40 feet tall and 25 feet wide, with dark green foliage and burgundy fall color.

'Palo Alto'
Orange-red to bright red fall color.

'Rotundiloba'
Rounded rather than sharply pointed leaves with fall color in yellow, red, burgundy and purple. Does not set seed.

'Slender Silhouette'
60 feet tall and just 8 feet wide, with orange-burgundy fall color.

'Variegata'
Green leaves with yellow streaks and splotches. Variegation turns pink in fall, and leaves turn red.

'Worplesdon'
Orange-red fall color.

Caring for liquidambar

Although these plants are not considered toxic, their spiky seed balls can be a physical hazard to grazing animals and barefoot humans. These trees have aggressive, invasive root systems that will interfere with underground pipes and hardscaped areas including sidewalks and driveways; make sure to plant them at least 40 to 50 feet away from any structures. Liquidambar trees do best when planted in full sun to partial shade. They like to grow in moist but well-draining soil that is slightly acidic (with a pH of between 5.0 and 7.4). Trees can tolerate clay soils as well as they are well-draining and not compacted. Apply a 2-4 inch layer of mulch around the base of trees to increase soil moisture retention, suppress weed growth, and regulate soil temperatures. After planting, make sure young trees receive regular waterings to help them establish a strong, healthy root system. Mature trees should be deep watered to encourage a root system that stretches farther down into the soil, but are considered moderately drought-tolerant.

Fertilize yearly in early springtime with an application of 2 inches of compost around the base of plants. Pull mulch back before applying, work the compost gently into the soil a bit, water it in, and then replace mulch. Prune these trees in late winter or early springtime, and remove damaged, dead, diseased or crossing branches at this time to maintain a healthy shape. Never top these trees, as this will destroy their natural, pyramid form and open them up to diseases. Pruning is generally not necessary except in certain circumstances. These trees are long-lived, typically surviving for 150 to 400 years or more under favorable conditions in their native landscapes. In gardens, their life span is significantly shortened to between 50 and 80 years. They grow at a medium to fast rate, reaching their mature size in 10 to 20 years.

Propagation

Liquidambar can be propagated either by using cuttings or from seed. To ensure that your propagated plant will have the exact same qualities and characteristics as the parent plant, use the cutting method. If you would like to experiment and see what plant you can grow from seed, just keep in mind that it will not necessarily be the same as the parent plant. To propagate your Sweet Gum tree, follow the instructions below:

Propagating Liquidambar by Cutting

Gather your materials. You'll need a clean, sanitized, sharp pair of garden shears, rooting hormone, a pencil, and a 3-inch pot filled with well-draining compost or other organic material. A good substrate for propagation of cuttings is a light blend of 1/3 pasteurized soil or compost, 1/3 sand, vermiculite or perlite, and 1/3 coconut coir or peat moss.
In spring or early summertime, choose the plant that you'd like to propagate. Ensure that this plant has had a good watering the night before, as this will improve the chances your cutting will take root. Cut one or more 6 inch portion(s) of the end of a non-blooming branch and strip the leaves off of the lower half. Make a hole in your planting medium by pushing your pencil into the soil. Dip the end of the stem in rooting hormone, and plant it in your pot. Fill in soil around the cutting to support it, but do not pack it down too much.
Moisten with water, and ensure that the pot has good drainage. Your pot should be kept in warm, sunny conditions indoors (and not in direct sunlight). Water whenever your soil is dry under the top layer. After about four to six weeks have passed, your cutting should be rooted. When you notice new growth, you'll know you have roots.
Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring, when you can transplant it to its new home. Ensure that the last frost of the year has occurred before doing this, as it can seriously damage your new shrub.

Propagating Liquidambar by Seed

Keep in mind that the plant you get from seed will not necessarily mimic all of the characteristics of the parent plant. To propagate by seed, you will need a paper bag, a pot or tray filled with well-draining compost or other organic material, a spray bottle and a fork. The best potting medium for seed germination is a light blend of 1/3 pasteurized soil or compost, 1/3 sand, vermiculite or perlite, and 1/3 coconut coir or peat moss.
Harvest your seeds. The seeds are contained inside of spiky balls which develop holes and release seeds into the environment. This process happens in fall. The balls will begin to fall from the tree and litter the ground. Collect them and place them in a paper bag. Place the paper bag in a cool, dry, dark area while the rest of the seeds are released (shaking the bag can help this process move a little faster). Once seeds are out of the balls, they can be worked with.
Seeds need to undergo a period of cold stratification to germinate. To complete this process, place harvested seeds in a damp mixture of sand and potting mix in a sealable container or plastic bag, and place the container in the refrigerator for at least three months' time. Remove the seeds from their bed after the cold stratification period, and soak them in lukewarm water for between 12 and 24 hours. Viable seeds will sink, and any that float can be discarded, as they will not germinate.
Water your prepared seed tray or pot filled with soil, and ensure that good drainage is occurring. Place your seeds in your prepared pot or seed tray about a quarter inch to a half-inch under the soil surface. Cover them with soil and water with your spray bottle. Place your tray of seeds in a warm area that receives bright, indirect light. A greenhouse is the most ideal climate, but a planting tray inside a window will do as well. Germination usually takes 7-14 days from sowing. Once you begin to see seedlings sprout and they are able to be handled, transplant them to their own individual 3-inch pots, filled with the same potting medium as described in Step 1. Loosen the seedlings from the potting medium by digging down with the tines of your fork about an inch and a half, gently working the seedling up until it is out. Then, replant the seedling in its individual pot.
Keep the seedling's potting medium moist, but not wet, by spraying the soil with your spray bottle. Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring (after the danger of frost has passed), when you can transplant it to its new home.

Liquidambar dried seed pods. Seeds are released through the small holes.

Seeds of liquidambar trees are small and winged.

Problems and Pests

These trees can cause a litter nuisance in the garden, especially if they are planted as street trees or overhanging patios, where consistent cleanup is required. Other than the issues they themselves create in the landscape, Liquidambar trees are susceptible to developing problems with the following pests and diseases: