styraciflua 'Gum Ball'5The Sweetness of Sweetgum
Mike Ecker, Director of Horticulture

The first time someone told me they had a pine crossed with a maple I was completely taken aback.  That’s not possible.  A second time a year or so later, another person described the same “hybrid.”  My answer was the same.  Another year or two…  a third time … and it finally dawned on me there was more to this than met the …. well, it just had to meet the eye!  I asked for a sample which I should have done the first time.

Turns out it was a sweetgum (Liquidambar styraciflua).   And yes, when leaves and stems are crushed they smell somewhat like a pine.   And its leaves do resemble those of some maples.  Hence the impression this tree is a cross between a pine and a maple.

Sweetgum leaves have 5-7 lobes with each lobe long and pointed.  The overall shape is that of a star, and leaves are glossy green with long and slender stalks (petioles).

For people who care about such things, sweetgum has traditionally resided in the witch-hazel family (Hamamelidaceae).  Some molecular researchers (think plant DNA) are currently evaluating sweetgum’s position in the botanical hierarchy.

Sweetgum has several great ornamental characteristics that make it a wonderful addition to the landscape.  While young they grow relatively fast with a consistent conical habit.  The glossy yellow-green foliage in summer is relatively free of insect pests and fall color can be yellow, orange, red, purple or combinations thereof.   Twigs bear corky wing-like growths that in winter catch snow, creating a very picturesque scene.  This last feature varies from one plant to another unless it’s a cultivated variety specifically selected for that trait such as ‘Corky’.

Bark on mature trees is furrowed into narrow, scaly ridges… not unattractive, but not standing out as particularly notable when compared to other trees that have ornamental bark.

One drawback of sweetgum is fruit production.  The insignificant flowers develop into hard, spiny balls about 1” wide that, after persisting for up to a year, drop beneath the tree.  Here they lay for several more years before finally decomposing into the soil.  In the interim they are a nemesis of bare feet, become formidable “mowing missiles”, and are a cause of complete frustration to those who just can’t stand the fact that trees, being living organisms, occasionally drop things in the lawn.

Some say there are selections of sweetgum that are fruitless; however, every selection that has reached reproductive age at The Dawes Arboretum has produced fruit.  Some selections have just taken a bit longer than others.  Trees produced from seed can take up to 25 years to produce fruit.  Grafted selections take less time to do so.

I was told once that if the spiny fruit balls are collected and used as mulch around plants that rabbits find appetizing, the animals would refuse to walk over them to get to a plant.  Perhaps a rabbit’s soft, furry feet don’t like the feeling either?  This sounds a bit like an urban legend to me and if you try this please let us know the results.

Sweetgum is found natively on rich, moist bottomland, but it can be grown in dry or heavy clay soil.  It makes a suitable tree for landscapes because more often than not they consist of heavy clay.  It is a valued timber tree where wood has been utilized for a wide variety of applications.  The species is native from the eastern United States to central America, and this includes Ohio’s most southern counties.

Presently Dawes has 26 different cultivated varieties on grounds and in our nursery.  A few notable kinds you can see in our collection are:

‘Corky’ – selected for its heavy production of cork-like growth on twigs.  Our specimen becomes a nice red in fall; otherwise like the species.

‘Gum Ball’ – which describes the overall plant shape – round, dense, nice purple-red fall color.  The specimen in our Witch-hazel Collection is about 15’ high and wide (after 17 years); no pruning, but looks as if it was sheared regularly.

‘Silver King’ – a white and green variegated tree.  Makes for a bold statement in the landscape.  Able to withstand full sun to light shade.  To date this selection has not produced fruit.

‘Variegata’ and ‘Goduzam’ (Gold Dust®) are both variegated forms, with yellow blotches during summer that take on various shades of pink and red in autumn.

‘Slender Silhouette’ – apt name for a slender, upright form suitable for narrow planting areas;  has yellow fall color.