We all admire the colorful cascade of leaves from deciduous trees in the fall, but when needles start dropping from your favorite pine or spruce, it’s hard not to worry.
A little needle loss is natural for all conifers. But if it’s happening at the wrong time of year, or in large amounts, it could be a sign that something is wrong.
It could be caused by something minor like a dry summer or it could be a sign of a deadly fungal disease.
So how can you tell if the needle drop is a normal part of your plant’s lifecycle, or a red flag? That’s what we’re going to explore in this guide.
Here’s what we’ll cover:
7 Causes of Needle Drop in Conifers
This first cause might seem a little obvious, but I want to go over it because it’s not commonly known that some conifers are deciduous.
They’re uncommon in the garden, but they do exist.
1. Deciduous Conifers
Many of us imagine that all conifers are evergreens, but there are some species that are deciduous.
These will drop all of their needles in the fall and grow new ones in the spring.
Larches (Larix spp.) are the most famous deciduous conifers, with their needles turning brilliant yellow in the fall.
Dawn redwoods (Metasequoia glyptostroboides), bald cypress (Taxodium spp.), and golden larches (Psuedolarix amabilis) also do the same.
If one of these trees is shedding needles in the spring or summer, it’s not part of the natural lifecycle and will require investigation. But if it’s autumn, just enjoy the show!
2. Disease
Many different diseases can cause needles to change color and drop.
Dothistroma needle blight (Dothistroma septosporum) causes dark green bands and yellow or tan spots, while brown spot needle blight (Mycosphaerella dearnessii) causes circular brown or yellow spots.
After the needles become symptomatic, they’ll drop. Both of these fungal diseases are found in most pine species.
Junipers are subject to twig blight, caused by fungi in the Phomopsis and Kabatina genera.
Infection can cause entire twigs and stems to turn brown or yellow, often accompanied by black fungal spots.
The symptomatic foliage may persist or fall from the tree.
Needle cast caused by Rhizosphaera kalkhoffii or Stigmina lautii causes discoloration and drop in spruce trees.
In Douglas firs, needle cast caused by Rhabdocline species and Swiss needle cast (Phaeocryptopus gaeumannii) causes browning or yellowing and falling foliage.
Lophodermium lacerum affects grand fir (Abies grandis) and balsam fir (A. balsamea).
If the needle death is appearing on the exterior of the tree or you see shedding during a time of year that’s not normal, it’s worth taking a sample to your local university extension office to confirm whether or not it’s caused by a disease.
You can then treat accordingly.
3. Drought
If the weather has been dry for a long time, especially during hot temperatures, it’s entirely possible your tree is experiencing drought stress.
Often, the first sign is yellowing of the needle tips. The new growing tips might die, as well.
During periods of drought, conifers may also drop needles as a way of conserving moisture, reducing the amount of foliage that requires moisture.
Sometimes the needles will turn yellow, but often they’ll just dry out without changing color at all.
If you’ve ever swept up needles after your living Christmas tree was past its prime, that’s what they look like.
A few weeks of drought usually isn’t enough to cause stress in established, healthy specimens but extended drought, especially over several years, can cause problems.
Of course, the solution here is to make sure your conifer is receiving the right amount of water, which varies according to the species.
A juniper might be fine while a redwood might be in serious trouble in the same environment.
Being familiar with the needs of the species you are growing means you can irrigate accordingly.
4. Heat Stress
Some conifers are sensitive to extreme heat. Well, any plant is susceptible to stress during prolonged periods of exceptional heat, but some species suffer in seasonal heatwaves.
Douglas fir (Pseudotsuga menziesii), silver fir (Abies alba), Norway spruce (Picea abies), and Atlas cedar (Cedrus atlantica) should all be protected from prolonged heat and you should avoid growing these species in hot, humid climates.
The Pacific Northwest, also known as conifer heaven, has recently had several years of extreme heat in the summer with record-breaking temperatures. The local firs, pines, and cedars have taken a real beating.
The university extension offices were flooded with samples and images of landscape trees looking decidedly worse for wear. But even if you aren’t experiencing shocking heatwaves, higher than average temperatures can cause your conifers to suffer.
Heat stress typically shows up as brown needles on the exterior parts of the plant. The younger growth is more susceptible to damage and it generally turns brown and falls off first. Continued stress will cause older foliage to do the same.
There isn’t much you can do unless your conifer is growing in a container and you can move it somewhere cool during a heatwave.
Otherwise, just keep the soil moist and if the tree is small or you’re growing a shrub, consider propping an umbrella or shade cloth over it during the heat of the day.
5. Injury
Anything that causes injury to a tree can result in dropping foliage. The two major concerns are root damage and herbicide injury.
Root damage can come in the form of rot, which can be caused by a disease or by drowning roots with too much water, but it can also be something as simple as compacting the soil by driving over the roots or chopping some up with the lawn mower.
Herbicide damage, on the other hand, is harder to identify. You don’t have to spray the plant directly, either. Drift on the wind when you or a neighbor is spraying nearby can cause damage.
Herbicides are made to kill plants, and while some species are resistant, others might not be.
The tolerance varies depending on the type of herbicide and the species it is used on. Dormant trees are usually tolerant to glyphosate, though it will harm any living tree.
Spruces and firs are sensitive to simazine, all conifers are sensitive to picloram, and spruces are sensitive to phenoxy-type herbicides.
One clue to whether needle drop is a result of herbicide damage is if all the plants in the area show some type of damage – even if they are different species.
There are few diseases that will affect roses, conifers, Japanese maples, echinacea, and lettuce, so if you had all of these growing in the same area and all of them were looking bad, the first thing I’d consider is herbicide damage.
6. Pest Infestation
There are lots of insects that feed on conifers and almost all of them can cause needle drop depending on the severity of the infestation.
Spider mites are a super common pest. They love the same hot, dry conditions that many pines and junipers thrive in and they’ll feed on the plant using their sapsucking mouthparts.
As they feed, the needles turn yellow or red and fall like raindrops. Scale insects do similar damage.
Borers are the other major pest to watch for. Bark beetles, pine moths, clearwing moths, pine weevils, and more will chew on the plant material and cause needle discoloration and drop.
The species of pest depends on the species of conifer and there are many different types, so it’s a matter of understanding the particular ones that attack your particular plant.
7. Seasonal Drop
All evergreens drop some needles over the course of their lives. The needles don’t have an indefinite lifespan and at some point they will age and die, dropping to the ground.
The lifespan of the needles depends on the species, but most live for a few years before they need to be replaced.
I can tell you that the first time my Japanese white pine started shedding its needles, I went into full panic mode.
Luckily, before I started pulling out my hair, an arborist friend told me that all was well and it was totally normal.
Conifers with scale-like leaves also drop their foliage as it dies off. More than one gardener has had their own mini panic when their western cedar or arborvitae started turning brown.
A small percentage of leaves turning brown or yellow and falling is totally normal. The trick is to understand the shedding process of your particular species.
Arborvitae shed in the fall, when some of the inner branches turn brown. They tend to hang out for a few months before shedding.
In Japanese pines, come late summer, inner needles turn yellow and fall. Yews drop in spring.
White pines are known for terrifying their owners since they tend to shed a bunch all at once in the fall, where most spruces tend to shed just a few here and there gradually year-round.
Junipers shed in the late summer and may or may not turn brown before they do.
Western red cedars shed late summer, but it can take a few years after the foliage turns brown before they drop.
As a broad overview, arborvitae, Australian, Scots, and white pines persist for about three years. Red pines last four years. Junipers stick around for a decade or so.
Spruce needles last anywhere from four to 10 years.
My advice is to familiarize yourself with the lifecycle of your particular conifer. You will also know that it’s not the normal seasonal drop if the color change is happening on the tips of the branches.
The tips are where the younger needles emerge and these shouldn’t be shedding before the older ones.
Keep It Green
Needle drop isn’t always a cause for concern, it’s often a perfectly natural part of the conifer’s lifecycle.
But when foliage starts falling at the wrong time of year or in unusually large amounts, it’s time to take a closer look.
By learning how your specific species behaves, you can quickly tell the difference between normal seasonal shedding and a symptom of stress or disease.
Whether it’s caused by drought, pests, or an unexpected heatwave, early action can mean the difference between recovery and decline.
What symptoms are you seeing? Are you having trouble figuring out the cause? Let us know in the comments section below and we can try to help you out. Pictures help a lot!
And for more information about how to grow conifers in your landscape, check out these guides next: