Get free expert answers to your tree care questions from ISA Certified Arborists. Browse answered questions or submit your own.
Our arborists typically respond within a few days. Your question will be published to help others with similar issues.
47 answered questions
Those raised, shiny black spots are tar spot Rhytisma species, a fungal disease that's very common on maples — especially Norway, silver, and red maples....
Brown blotches with purple margins on a flowering dogwood, combined with branch dieback, point to dogwood anthracnose Discula destructiva — a serious fungal...
Good news: browning on the inner needles of pines, arborvitae, and other conifers in late summer or fall is usually seasonal needle drop — a completely normal,...
The spotted lanternfly Lycorma delicatula is an invasive planthopper spreading rapidly through the eastern US. While it rarely kills established trees...
Those 1-2 inch spindle-shaped "bags" covered in bits of foliage are bagworms Thyridopteryx ephemeraeformis — caterpillars that build a protective case from the...
Fluffy, cottony white masses on twigs and branches are usually the protective wax of sap-feeding insects — most often woolly aphids, cottony cushion scale, or...
Leaves chewed down to a lacy skeleton in mid-summer, with metallic green-and-copper beetles clustered on them, are the work of Japanese beetles Popillia...
The best time to prune apple and most other deciduous fruit trees is late winter to early spring — while the tree is dormant but before buds break roughly...
"Crape murder" is the all-too-common practice of topping crape myrtles into ugly stubs each year. It's unnecessary and harmful — proper crape myrtle pruning is...
Improper watering — usually too little, sometimes too much — is the number one killer of newly planted trees. A new tree has lost most of its root system and...
The right distance depends on the tree's mature size, not the size at planting. A common, costly mistake is planting a future 60-foot shade tree 8 feet from...
Everyone wants shade fast — but the fastest growers silver maple, Bradford pear, cottonwood, Siberian elm tend to have weak wood, invasive roots, or messy...
Tree removal cost varies widely by size, species, location, and complexity, but here are realistic US ranges to set expectations. Typical cost ranges: - Small...
It depends entirely on where you live — there is no single national rule. Many municipalities, especially in the West and in HOA communities, regulate tree...
Brown, wilting leaves on an oak in mid-summer are a classic red flag for oak wilt Bretziella fagacearum, one of the most destructive tree diseases in the...
A hollow tree is not automatically doomed — many hollow trees stand safely for decades. What matters is how much sound wood remains in the trunk wall, not the...
Black spots on spruce needles are most commonly caused by Rhizosphaera needle cast Rhizosphaera kalkhoffii, a fungal disease that is extremely prevalent on...
Surface roots heaving sidewalks are a common headache, but the good news is that roots rarely damage sound foundations directly — and there are ways to manage...
The white powdery coating on your tree's leaves is almost certainly powdery mildew, one of the most common and easily recognized fungal diseases of trees and...
Lots of trees have compound leaves multiple leaflets on one stalk and get mistaken for ash. With emerald ash borer killing ashes everywhere, correctly telling...
Those striking orange gelatinous masses are the telial horns of cedar-apple rust Gymnosporangium juniperi-virginianae, a fascinating fungal disease that...
Oaks Quercus all share lobed or toothed leaves and acorns, but there are dozens of species. The first and most useful split is into two big groups: the red oak...
Dark liquid oozing from bark — called slime flux or bacterial wetwood — is a common condition caused by bacteria fermenting sap inside the tree. While it looks...
Mulch is one of the best things you can do for a tree — but the "mulch volcano" a tall cone of mulch piled against the trunk is one of the worst. Done right,...
Many homeowners fertilize trees out of habit, but most established landscape trees don't need it — and over-fertilizing can do real harm. The key is to...
D-shaped exit holes in an ash tree are the unmistakable calling card of the emerald ash borer EAB Agrilus planipennis, the most destructive forest insect pest...
Yellowing leaves in summer not fall — called chlorosis — means the leaves aren't producing enough chlorophyll. The pattern of yellowing is the clue to the...
Small green caterpillars often called "worms" feeding on tree leaves could be several species, but the most common culprits are cankerworms, inchworms, fall...
Wilting on a newly planted tree is usually transplant shock — the tree lost most of its roots when it was dug or potted, and the remaining roots can't yet...
Tiny holes with accumulations of fine sawdust called frass at the base of your tree indicate boring insect activity. This is a serious concern because...
That sticky substance coating your car and everything else under the tree is honeydew — a sugary waste product excreted by sap-sucking insects. It's not sap...
In Wisconsin and throughout the Upper Midwest, the timing of oak pruning is critical because of oak wilt disease. The sap beetles Nitidulidae that spread the...
The general rule of thumb is to never remove more than 25% of a tree's canopy in a single growing season. For maples specifically, being more conservative —...
This is one of the most common tree care myths. In most cases, NO — you should not apply wound sealant, tree paint, or pruning paste to cuts. Research...
Yes — dead branches can and should be removed at any time of year. Since the wood is already dead, the timing restrictions that apply to live-wood pruning...
USDA Hardiness Zone 5 covering much of the upper Midwest, including Wisconsin, Minnesota, Iowa, and parts of surrounding states has excellent options for...
Fall is generally the best time to plant trees in most of the United States, with some important regional exceptions. Here's the science behind why. Why fall...
Planting too deep is one of the most common and most lethal mistakes in tree planting — and unfortunately, it's frequently done by landscapers, garden centers,...
Deciding whether to remove a tree is one of the most consequential decisions a property owner can make. Large trees provide thousands of dollars in...
A tree that has developed a new lean after a storm is a serious safety concern and should be evaluated by a certified arborist as soon as possible. A sudden...
Stump grinding is the better choice for most homeowners. It's faster, less expensive, and less destructive to your yard than full stump removal. Here's a...
Mushrooms at the base of a tree can be a serious warning sign, but not all fungi are created equal. The mushrooms you see are the fruiting bodies — the...
Trunk cracks are one of the most significant structural defects in trees, and they range from cosmetic concerns to imminent failure hazards. The type,...
Trees growing into power lines are a serious safety hazard that causes thousands of power outages annually and can create life-threatening electrocution risks....
Several beautiful tree species are known for their distinctive white peeling bark. Here are the most common ones in North America, with tips to tell them...
A tree with 5-lobed leaves and helicopter seeds technically called samaras is almost certainly a maple Acer species. Maples are the only common North American...
A tree with large, branched thorns growing directly from the trunk is almost certainly a honey locust Gleditsia triacanthos, one of the most distinctive trees...