Ask Mr. Smarty Plants

As we researched your question, we realized that Tsuga canadensis (eastern hemlock),  which is native to South Carolina, is a pretty finicky plant.  When you have a plant having unexplained problems, you have to look at the environment of the plant, not just now, but for the last couple years. If you purchased the plant from a nursery in a pot, and transplanted it into the native soil, the roots may have just now (since it's been planted less than two years) gotten in contact with that soil. 

Here are the Condition Comments on this plant from our Native Plant Database:

"Conditions Comments: Eastern hemlock can be a fast-grower, but is more often slow-growing. It must be placed where there is good drainage and no strong, drying winds. Trees seem somewhat pH adaptable but prefers acidity. They can be restrained as a hedge for years with regular pruning. Sunscorch kills back branches, and drought kills the tree. A number of diseases and insects can be troublesome, but trees in good health prove reliable."

There are several clues in those Comments, possibly the most telling one is "drought kills the tree."  The conditions that the tree has had to withstand last year and this year would be a trial to any plant, especially a young one like that. First, it was drought, now, this year, it's flooding. Are you sure you are getting good drainage? What is generally called "clay loam" in soil analysis is about 25% clay, 30 to 50% silt and the rest sand. This is not necessarily a particularly fertile soil, and probably not well-draining. If you were watering it heavily last year, and the drainage was not good, the roots could have been drowning last year, and are really drowning this year. It prefers acidic soil, and needs part shade (2 to 6 hours of sun a day) to shade (less than 2 hours of sun a day. We tried to ascertain if your soil was acidic or alkaline, and couldn't find any indications either way. Sometimes plants which need acidic soils but are planted in alkaline soils become chlorotic, losing the green color in their leaves. 

Read all of this Ohio State University website Tsuga canadensis,  which details the many problems of the tree. Especially, we noted this excerpt from that site:

"Canadian Hemlock is somewhat sensitive to being transplanted in Autumn, and care should be taken to amend the soil, fertilize, water thoroughly, mulch adequately, and avoid Winter salt spray, to enhance survival chances during the first Winter."

We found a list of hemlock stressors, or insects and diseases: hemlock wooly adelgid (Adelges Tsuga Annand), elongate hemlock scale (Fiorinia externa), hemlock looper (Lambdina fiscellaria), spruce spider mite (Oligonychus umunguis), hemlock borer (Melanophila fulvoguttata), root rot disease (Armillaria mellea), needlerust (Melampsora parlowii). If you examine these linked websites, perhaps you will recognize some of the symptoms you have detailed for us. 

Bottom Line: Since we are gardeners, not entomologists nor plant pathologists, we can't possibly diagnose the problem(s) from a distance. Furthermore, our soils are very alkaline in Austin and we're in extreme drought, so there would be no possibility of a hemlock flourishing here. Best guess: We think your tree was in trouble from the time it was planted. It probably should not have been planted in the Fall, the soil needed extensive amendment to improve drainage, and a raised bed would have been better still. Working compost into the soil, mulching to protect the roots and checking the drainage of your soil could help, but too much damage may have already been done.

If you would like to try to save your tree, we suggest you contact a trained and certified arborist to look at it and determine what, if anything, can be done. You might contact the Clemson University Extension Office Greenville County for information and possibly a list of experts that could help you. 

Tsuga canadensis

Tsuga canadensis

Tsuga canadensis

Tsuga canadensis