This time of year can reveal some pretty striking brow patches on evergreen trees and shrubs.
The question always comes up “Is the browning indicating a decline in the plant?
Is the plant going to be OK?” the answer is “It depends……”
Seasonal needle drop in the fall is a natural occurrence. In most cases, the plant is fine.
https://bygl.osu.edu/node/2040
Two great examples are White Pine and some Arborvitae.
White Pine, Pinus strobus, can lose up to a third of its needles in the fall which is normal.
Homeowners become alarmed and the yellow needles on the tree as well as the needles that fall on the ground along with pinecones.
But all this is normal for White Pine to shed some of their needles, although not all will shed at the same rate or same time.
In addition, even Weeping White Pine, Pinus strobus ‘Pendula’, will shed some needles.
Another common tree that will shed in the fall is American Arborvitae, Thuja occidentalis.
The tree will show consistent brown branches which can alarm people.
But not all Arborvitae will show brown.
Emerald Arborvitae, Thuja occidentalis ‘Emerald’ , may show no browning.
You can see the two Arborvitae next to each other. One is browning (American Arborvitae - the plant on the right), the other is not (Emerald Arborvitae - the plant on the left).
But in other cases, the whole Arborvitae might be brown.
In this case, the tree is probably not going to survive. On closer inspection, these trees are suffering from too much water. Arborvitae hate wet feet! Note the standing water in front of this planting.
As you inspect your evergreen, keep an eye open for Bagworm. This time of year, the bags are fairly large and obvious.
If possible, they can be removed by hand and destroyed.
Bags may be on a number of different trees and shrubs, but Bagworms seem to favor evergreens like Arborvitae and Blue Spruce.
https://bygl.osu.edu/index.php/node/1439
Another common complaint is the entire tree turns yellow. In the case of a White Pine, this is bad!
A closer look revealed a septic line that was saturating the planting.
The yellowing tree eventually died!
But in other cases, with trees like Dawn Redwood, Metasequoia glyptostraboides,
Bald Cypress, Taxodium distichum,
or American Larch, Larix laricina,
(photo courtesy of Ann Chanon)
the trees are fine. All these trees are narrowleaf, deciduous trees. In the winter they will be totally bare but come spring with leaf out and be totally fine.
https://bygl.osu.edu/node/2125
So, the answer from the beginning is “It depends…...”
Identifying the tree correctly is the first step in determining whether the tree is just acting normal or showing signs of distress.