Chapter 105 Liquidamber styraciflua
105.1 Sweetgum
A sweetgum developing its fall colors. Some trees’ leaves turn dark red bordering on purple. Sweetgums develop beautiful flaking bark, but are challenging because they have very large leaves. Link to original image.
105.2 Soil: Moist Deciduous Mix
Ratio: 4 parts bark, 1 part grit
Add-ins: dolomitic limestone (~5 lbs/yd), Tree-Tone (15 lbs/yd)
pH: ~6.5 (slightly below neutral)
Moisture: Average
Light: Full sun.
105.3 Cultivation Notes
105.3.1 Potting & Root Pruning
Repot every two years in spring as buds extend.
105.3.1.1 Top & Branch Management
Heavy pruning: like birches, sweetgums do not react well to pruning during dormancy; it can cause dieback of branches and poor wound healing. Try to limit pruning to the growing season when the tree is active.
Scars can take a long time to heal but do heal quicker if wounds are made during the growing season.
Fine pruning: prune to shape throughout the growing season paying special attention to pruning back the apical or top growth, failure to do this can lead to weakening and dieback of lower branches.
Sweetgums produce ‘sprays’ of leaves from shoots, similar to gingkos.
Leaf pruning: reacts well to leaf-pruning.
105.3.2 Feeding
Every two weeks during the growing season.
105.3.3 Pests & Problems
No major pests.
105.3.4 Winter Storage
Frost protection required below -10°C. Shelter from freezing winds. Store in mulch outdoors. Try to place in a shaded area so buds do not break in a mid-winter warm spell.
105.4 Propagation Notes
I have never tried to grow these from seed. The sweetgums in my collection are all grown out from commercial liners.
105.5 Artistic & Styling Notes
Liquidamber can be difficult to style as bonsai; there is a tendency for branches to die back or weaken. Growth is also coarse, with long internodes. Smaller trees in group plantings seem to stay more compact.
105.6 Additional Information
105.6.1 Natural History
Sweetgum is native to moist woodland in areas of eastern USA and Mexico where it reaches heights of up to 80 feet. Mature trees are broadly conical, upright with an open canopy.