My slender silhouette sweetgum tree leaves turning red in July


Hi our slender silhouette sweetgum trees have been planted professionally in late October, 2022 and it took them until the first two weeks of June to fully develop leaves. The leaves are somewhat scare in some parts of the trees and some branches died. Most troubling is the fact that not only they are bright green as opposed to deep dark green, they started turning red at the end of July. Some also have fallen off. Those leaves were either pale yellow or green with red parts and dried brown tips. I check the soil and the ph is at 7 and wet with full sun exposure. What could be causing this problem? I’m scared the trees are under some stress and are lacking nutrients. I have used fertilizer spikes at the end of July and started watering each tree for 90 seconds to two minutes. I’m scared my trees are shutting down for the season and/or dying. It’s very stressful as we’ve paid a lot of money for the trees and planting. Any advice? Thank you.


What striking trees you have planted!

The slender Silhouette Sweetgum, Liquidambar Styraciflua ‘Slender Silhouette’ is a narrow columnar variety that can grow to 15m tall and 2m wide.  Leaves are dark green and, in the fall, could be shades of yellow, orange, red, or burgundy.

These trees like full sun and are intolerant of shade.  They prefer deep, fertile moist, well-drained soils, but will tolerate a wide variety of soils.  Alkaline soils should be avoided.

This tree is rated hardiness zone 6, so it should overwinter in Toronto.

Transplanting is a major stress for all trees, and they often take some time to get established. Adequate water is especially important for new trees.

In Planting a Tree for Life: A Toronto Master Gardeners Guide we recommend the following after care for new trees:

Water regularly for the first few years of your tree’s growth, checking to make sure the soil has not dried out.  If there is not much rain, gently pour two large buckets of water over the soil once or twice a week or let the hose slowly trickle down the same amount of water. However, don’t overwater.  If water is pooling around the tree and the soil is very wet, cut back on your watering and water less frequently.

A sprinkle with the hose for a couple of minutes does more damage than good as this does not provide enough water to penetrate deep into the soil.  Newly planted trees must be watered regularly until frost.

Maintain a 2 to 3” mulch layer of leaf litter or wood chips around the base of the tree, a home to countless organisms and a source of valuable nutrients as it decomposes. Mulch forms a barrier which reduces evaporation and traps water, allowing moisture to drain slowly into the soil. It will also suppress weeds and makes their removal easier while protecting the soil structure and moderating swings in soil temperature.

Keep the root zone free of grass and weeds to allow all the nutrients to be directed to your tree.

Following the above watering regime for your sweetgums could be the key to getting your trees to thrive.  New trees generally do not need additional fertilizer, so do not fertilize the trees any further.

Note – if a tree has not been well cared for at the tree farm where it was grown, it may not survive, even with good after planting care due to stress.

You should also contact the nursery where you bought the trees from for their advice on what to do.  If you acquired them through a 3rd party such as a landscaper or garden designer, please contact them to let them know you think your expensive trees are in trouble.  Reputable nurseries and horticultural businesses have plant guarantees, and will usually replace a dead plant within a certain timeframe.