Tree care is a critical investment for the future of your landscape. And while brown leaves, dead limbs, and other common problems don't always mean you have a dying tree, it's important to take notice of such troubling signs and learn their causes. In many cases, the causes are specific to the type of tree.
Brown leaves on Japanese maples often are related to over-exposure to sun, commonly known as "leaf scorch." This can be aggravated by problems such as lack of water, too much fertilizer, damage to roots, and exposure to strong wind, all of which can stress the tree and leave it vulnerable to the sun.
Brown leaves appearing on magnolia trees in spring can indicate frost damage. This can ruin the tree's appearance for awhile but is unlikely to kill the tree. If browning appears in summer, inadequate watering may be the cause, although high winds could also be the culprit because they dry out the foliage. Leaves with black spots are likely caused by a fungus that thrives in moist conditions, making this a common problem in humid climates.
Bradford pears trees that have recently been transplanted often experience transplant shock, leading to a host of potential problems, including leaf wilt, leaf scorch, yellowing leaves, and leaf rolling or curling. Wind can make leaf wilt and other problems worse. Don't assume you need to water a tree more just because it has brown leaves when its foliage would normally be green.
In the case of Bradford pear leaves turning black (not yellow or brown), the cause may be fire blight disease, so called because it causes tree parts to turn black.
Emerald cedar, or 'Emerald Green' arborvitae, commonly develops brown leaves in summer. This can be due to several factors, including insects, diseases, and even dog urine.
Of course, the problem also can be simply due to drought. Brown leaves on the inner part of Emerald cedars are normal during fall and spring, but leaves turning brown at the outer tips of branches can indicate serious problems.
Yellow or brown needles and branch dieback on Colorado Blue Spruce are commonly caused by two insects: aphids and the Cooley spruce gall adelgid. These problems also can result from infection by cytospora canker and various needlecast diseases.
Needle drop on evergreens can be scary, but it's not necessarily fatal. In the case of dwarf Alberta spruce, the cause of needle drop often is lack of water or, conversely, too much water. Examine your tree's location to help determine which problem fits best. If the tree is planted in poorly draining soil, its roots may be sitting in too much water, and the solution may require moving the tree to a better location with permeable soil and plenty of sun.