Why Is My Green Giant Turning Yellow?

A yellowing Green Giant is often doing something normal. All arborvitae shed some foliage, and Green Giants change color with the seasons. But the same yellow can also be the first visible sign of trouble in the roots, soil, or foliage. The useful question is not only why the tree is yellow, but where on the tree the yellow is and when it appeared.

Normal Yellowing You Can Ignore

Evergreens regularly shed their oldest foliage, the part that sits closest to the trunk.1Cumberland Valley Tree Service – Landscaping. Winter Plant Health Care Guide: Seasonal Needle Drop So yellowing and dropping on the inside of the tree is usually seasonal shedding.2Cumberland Valley Tree Service – Landscaping. Winter Plant Health Care Guide: Seasonal Needle Drop Browning or yellowing on the outer branch tips, or moving from the top down, is a different story and a reason for concern.3Cumberland Valley Tree Service – Landscaping. Winter Plant Health Care Guide: Seasonal Needle Drop

To check, part the branches and look in toward the trunk to see where the yellow is concentrated. Inner yellow or rusty foliage that falls off when you run a hand through it is usually shedding. If the fresh outer growth stays green, the tree is fine. A tree that looks sparse only deep inside is usually fine too.

Green Giant can also take on a slightly yellowish tone in cold winters, especially in exposed or windy spots.4Perfect Plants Nursery. Thuja Green Giant Tree Problems This tint is normal and temporary, and the foliage should return to its dark green once spring arrives.5Perfect Plants Nursery. Thuja Green Giant Tree Problems Yellowing that persists into late spring, after other plants have greened up, is not the winter tint.

Timing helps you tell the two apart. Seasonal shedding mostly shows in late summer and fall. A whole-tree tint that starts in deep winter fits cold and wind exposure. Take a dated phone photo now so you can compare in spring.

Reading the Yellow to Find the Cause

Where and how the yellow appears narrows the field quickly:

Treat each pattern as a lead, not a diagnosis. Yellow on new growth fits iron shortage, but alkaline soil, wet roots, and root damage can all produce similar yellow, so the soil and drainage around the tree matter.

Check whether the neighbors match. One sick tree in a healthy row suggests a local cause such as drainage or a dog. Then move to harder checks, like a soil test or a close look at the foliage with a magnifier or your phone’s zoom.

Problems can also overlap. A tree weakened by soggy roots is more prone to other problems, and may pick up mites or blight, so fixing one cause may not clear everything.

Too Much Water and Root Rot

Green Giant demands well-drained soil.14Perfect Plants Nursery. Thuja Green Giant Tree Problems So a tree in a low or clay spot can yellow even when it gets plenty of water.

Water often collects where you don’t expect it: at the bottom of a slope, beside a downspout, or in a clay spot that drains slowly after every rain. One tree in a row can sit in a wet pocket while its neighbors are fine. Roots need air as well as water. In saturated soil the air spaces fill, so roots weaken and stop taking up water and nutrients, and the foliage can yellow as if the tree were thirsty. Because the symptoms look like drought, many people water more, which makes things worse. Check the soil before adding water.

Soggy or clay-heavy soil invites root rot, a soil-borne disease that spreads through the roots.15Perfect Plants Nursery. Thuja Green Giant Tree Problems Green Giants are susceptible to root rots, including phytophthora and armillaria, which can kill them.16Beaufort County Center. My Trees Are Turning Brown Poor growth with reddish-brown foliage and decline despite good care can be a sign of root rot.17Perfect Plants Nursery. Thuja Green Giant Tree Problems It can also spread to nearby plants.18Perfect Plants Nursery. Thuja Green Giant Tree Problems

To check drainage, dig a hole about a foot deep near the tree, fill it with water, and see whether it drains within a few hours. Soil that stays wet or smells sour days after rain is a warning. So is a handful that drips or forms a sticky ball when squeezed.

If drainage is the problem, cut back irrigation and water only when the top few inches are dry. Redirect downspouts and sprinkler spray away from the row. For replanting, choose a raised or better-drained spot. A tree that is dying from root rot should be removed so it doesn’t spread to neighbors, but ask an arborist or extension office to confirm root rot before removing trees that still look healthy.

Nutrient Shortages and Poor Soil

Nutrient shortages show up as yellowing.19Nature Hills Nursery. Common Arborvitae Problems and How to Fix Them Iron shortage yellows the newest growth, while nitrogen shortage makes the whole tree pale green to yellow.20Nature Hills Nursery. Common Arborvitae Problems and How to Fix Them A yellowish cast a few weeks after planting can point to nutrients rather than disease, though transplant stress and watering problems can look similar.21Perfect Plants Nursery. Thuja Green Giant Tree Problems

Shortages are most common in very sandy soil, where nutrients wash out quickly.22Nature Hills Nursery. Common Arborvitae Problems and How to Fix Them In alkaline soil above pH 7.5, iron becomes unavailable to the tree.23Nature Hills Nursery. Common Arborvitae Problems and How to Fix Them Trees competing with lawn grass for nutrients are also at risk.24Nature Hills Nursery. Common Arborvitae Problems and How to Fix Them

A soil test from your extension office shows pH and missing nutrients cheaply, and the results tell you whether the problem is soil or something else entirely. If pH is above 7.5, adding fertilizer alone won’t fix iron yellowing.

To feed, apply a slow-release balanced fertilizer made for large evergreens, following the label.25Perfect Plants Nursery. Thuja Green Giant Tree Problems Once a year is usually all a Green Giant needs.26Perfect Plants Nursery. Thuja Green Giant Tree Problems Overfeeding can burn roots, so don’t double the label rate.

Pull lawn back from the base of the tree so grass doesn’t take the nutrients. A ring of mulch a few inches deep holds moisture and feeds the soil as it breaks down, as long as it stays off the trunk. Be careful when edging, since cutting roots causes its own yellowing.

Spider Mites, Leafminers, and Tip Blight

Spider mites suck juices from foliage, leaving a very fine yellowish speckling.27Hortsense. Arborvitae: Spider mites Conifer mites can leave foliage bleached, bronze, reddish, or yellow.28UC Statewide Integrated Pest Management Program. Why Is My Green Giant Turning Yellow? Heavy infestations turn foliage brown, weaken the tree, and cause early drop.29Hortsense. Arborvitae: Spider mites In bad attacks you can see fine webbing.30Washington State University Extension. Recognition and Management of Christmas Tree Pests

To confirm mites, hold a sheet of white paper under a branch and tap the branch sharply. Tiny specks that start to crawl across the paper are mites, while specks that stay still are probably debris. Mites are most active in hot, dry weather, so check then. A strong spray of water on the foliage can knock many of them off and is a gentle first response. Confirm mites before using any treatment, because the speckling can resemble other problems.

Arborvitae leafminer larvae feed inside the foliage, which turns yellow, then brown and dry, and may fall.31Arboriculture & Urban Forestry. Relative Susceptibility Among Arborvitae Cultivars to Arborvitae Leafminer, Argyresthia thuiella (Lepidoptera: Argyresthiidae) Leafminer tips look hollow and papery when held up to the light.

Tip blight is a fungal disease that starts at the foliage tips and moves toward the stem.32Wasco Nursery. Arborvitae Needle Blight: 5 Symptoms and the Best Fix Infected foliage goes from green to yellowish to dark brown or almost black.33Bartlett Tree Experts. Pestalotiopsis Tip Blight on Arborvitae Twig tips may show tiny black pinhead-size dots, where the fungus produces spores.34Bartlett Tree Experts. Pestalotiopsis Tip Blight on Arborvitae Tender young growth is infected first, and shoots turn dull red-brown as it spreads.35WSU Extension. Arborvitae: Twig blight

That near-black color and those dots are what separate blight from leafminer. If it’s blight, snip off affected tips and bag them rather than composting. Prune in dry weather so the fungus spreads less.

Salt, Dog Urine, Weed Killer, and Root Injury

Evergreens are very susceptible to salt, and trees near roads are likely to be affected.36University of Illinois Extension. Road Salt damage to Arborvitaes Salt spray browns foliage from the tip inward, and branches go bare on the road side.37Arboriculture & Urban Forestry. Why Is My Green Giant Turning Yellow?

Salt follows the road: the side facing the pavement browns or thins while the far side stays green. It arrives as spray thrown from passing cars and as runoff soaking into the soil, and both can injure the same tree. Winter burlap screens on the road side cut the spray. In spring, hose off the foliage and soak the soil to flush salt down past the roots. Use sand or salt-free de-icers near plantings.

Dog urine is high in nitrogen and salt.38Nature Hills Nursery. Why Are My Arborvitae Turning Brown? | Causes & Fixes | Nature Hills Repeated visits burn the foliage it touches and can damage roots.39Nature Hills Nursery. Why Are My Arborvitae Turning Brown? | Causes & Fixes | Nature Hills Check the lowest branches for a dog’s favorite spot.

Twisted or curled growth can signal injury from lawn weed killers such as 2,4-D.40Arboriculture & Urban Forestry (AUF). Herbicide Injuries to Trees-Symptoms and Solutions These chemicals cause abnormal growth that disrupts the tree’s water flow and food making.41Arboriculture & Urban Forestry (AUF). Herbicide Injuries to Trees-Symptoms and Solutions Ask whether a lawn service sprayed on a windy day.

Root damage often shows as thinning or yellowing that doesn’t match the season.42Urban Tree. Tree Root Damage: 6 Warning Signs You Shouldn’t Ignore Digging, trenching, grading, or aggressive lawn edging can cut roots near the surface.43Urban Tree. Tree Root Damage: 6 Warning Signs You Shouldn’t Ignore Compacted soil slowly suffocates roots, so damage can appear months after construction ends.44Urban Tree. Tree Root Damage: 6 Warning Signs You Shouldn’t Ignore Recall any trenching for fences, irrigation, or utilities within the past year, and keep heavy equipment and vehicles off the root zone.

Will It Turn Green Again

Arborvitae tolerates pruning well, so you can trim off browned parts.45Kotona Living. Arborvitae turning brown—what to do? Expert answers to the most common arborvitae problems Keep watering as usual and watch for new green growth over summer.46Kotona Living. Arborvitae turning brown—what to do? Expert answers to the most common arborvitae problems Bare areas inside an arborvitae rarely fill in, though, because old wood seldom sprouts.

Nutrient yellowing improves over a season after feeding, and new green tips are the sign the tree is recovering. If outer foliage keeps yellowing after you fix water and soil, root rot is one possibility to have checked.

Several trees in a row declining one after another also suggests root rot. An arborist can confirm disease and suggest treatment, and your county extension office can identify samples, often free. Bring a bagged branch sample that includes both healthy and yellow foliage.

If a tree has to be replaced, plant in better-drained ground, and not in soil where root rot killed a tree. Keep new plantings back from salted roads and dog paths.