Having well over 100 species, pine trees can display wonderful variety. The US and Canada eastern white pine’s known for its regal habit, the lacebark has the most beautiful mosaic bark, and the tall Scots Pine dominates many forests in the UK, Europe and Asia.
I’ve often encountered the question – why is my pine tree dropping needles?
As a general rule, pine trees are expected to drop around a third of their inner needles each autumn. However, numerous factors can cause premature or extensive drop, including recent transplanting, drought, excessively wet soil, lack of sunlight, mite infestations, and fungal needle cast diseases.
Sometimes, the number of pine needles on the ground can seem startling. Sometimes the needles seem to fall in an odd distribution.
It’s my pleasure to use my science background and experience as a tree enthusiast to help you easily determine whether there’s a problem with your pine tree.
Do pine trees shed needles all year?
All pine needles are expected to fall eventually. Depending on species, pine needles usually stay on the tree for 2 to 4 years, or as much as 5, but they all eventually drop.
Pine trees should only lose significant numbers of needles between late summer and late autumn.
Needles are leaves – and once they’re no longer useful for absorbing sunlight for photosynthesis, the tree doesn’t hang onto them. The term ‘evergreen’ can be a bit misleading in this sense, making many think that it’s only deciduous trees that lose their leaves.
The outer ones, at the branch tips, get most of the sunlight, so pine trees will naturally drop some of their inner, more shaded pine needles every year (which are also the oldest). They turn brown before they drop off.
Identifying abnormal needle drop
How can you tell if pine needle drop is normal, or not?
You may have abnormal needle drop if:
- You’re losing more than about a third of the inner needles
- You’re getting significant needle drop in winter, spring or early summer
- You’re seeing outer needles (near the branch ends) turning brown or falling off, not just inner ones
- the needle drop is not symmetrical or affects mostly the top or bottom of the tree
- the falling needles have lines or spots visible on them
- the tree’s bark has marks, holes or oozing ‘cankers’ on it
Have a look at your pine tree and at the ground underneath. Are the fallen needles all right under the tree, around the trunk, as they should be? Are the recently fallen needles (or the ones on the tree) marked with lines or spots? Do you feel that the tree looks healthy? Read on for more answers.
Pine tree needles and wet soil
Pine trees, like many conifers, do not grow well in wet, marshy soil. This will be quite evident as the tree typically is growing slowly and has a wilted or sick appearance. Such trees will often experience excessive pine needle loss – more than the typical one-third of inner needles in a year.
It’s difficult to remedy this issue. If it’s not growing well, what I’d do (don’t shoot the messenger!) is to dig out the pine and start again in a dryer spot!
But then again, there are problems with ground that’s too dry as well…
Losing pine tree needles in summer
Loss of pine needles before late summer indicates a problem with the tree. Most commonly this indicates a lack of water. But how much water do they need?
Pine trees are typically intolerant of drought – in fact, it can be lethal. I find that they’re often planted on much thinner soil than they’re naturally used to, and because of their hardy appearance, gardeners don’t give them as much attention when watering.
Pine trees in drought can look brittle, and as they become more stressed, the needles can brown at the tips and drop off prematurely.
If the pine needles have already dropped, they won’t grow back – but you can usually remedy this one by starting some regular irrigation.
Pine trees, especially when young, need weekly watering during dry spells. Remember that you’re trying to get water to the deepest roots, so 5 or 10 minutes isn’t enough – the sun will simply dry the ground again. 30 minutes is more like it.
A sprinkler’s probably better than a hose – but try not to get too many of the needles wet, as this will increase susceptibility to fungal diseases – more on that later. But you could water in the morning, so that the sun will dry the needles out during the rest of the day.
A simple and effective way to prevent the tree from drying out is to apply a good layer of organic mulch, such as bark chippings, around the trunk of the tree – with a radius of 2-3 feet. Tree owners often neglect this, but practically every tree benefits from it.
The layer should be about 4 inches thick. Avoid it actually touching the trunk itself though, where it can contribute to trunk rot. The mulch stops the roots cool and stops them from drying out, helps rain to penetrate the ground, and prevents grass and weeds from growing (which compete with the tree for water). It looks good as well, providing a nice circular border for your tree.
Losing pine tree needles in winter
Exposure to the elements during the winter months can cause ‘winter injury’ to pine trees. As they keep their leaves (needles) in winter, they’re subject to a lot more evaporative moisture loss from wind and sun over winter compared to deciduous trees, which are protected by being leafless and dormant.
The sensitive needles can also be damaged by sudden cold snaps, snow and frost. The risk’s highest when the ground’s frozen, and the roots can no longer draw up water to replace the water that’s lost from transpiration, from the needles.
Signs of winter injury are often apparent in early spring, and include brown, prematurely dropping needles on the outer parts of the tree. Typically the discoloration starts at the needle tips and moves inwards. You may find that tree is mostly affected on one side: this typically will be the side that’s exposed to wind, sun or sometimes to salt spray from roads – typically seen in pine trees that line a driveway. Salt makes pine trees more prone to winter injury.
How to protect pine trees from winter injury
- Pine trees need to be watered in winter! A deep soak once a month will probably do it. This is particularly important if the temperature’s consistently been below 40°F (4°C). Having adequate water for the root will allow it to replace the moisture lost from the needles over winter.
- Mulch around the base of the tree properly. 4 inches or so will insulate the roots from temperature fluctuations, allow water to permeate and reduce risk of ground freeze!
- Consider some wind protection. If your pine’s losing needles or going brown on the exposed side, you may need a fence or at least a cover on that side. Arborists frequently use clear plastic sheeting, horticultural fleece or burlap – with the added bonus of frost protection.
- If you’re going to prune or shape you pine tree, do it in spring and early summer. If you prune in late summer, you might encourage growth that will still be young and temperature-sensitive when winter hits.
If the needle loss isn’t too severe, the pine tree will usually recover. But if it’s happening every year, it could affect the overall growth and vigor of the tree.
Needle drop in a recently planted pine tree
Excessive needle drop is actually particularly common if your pine tree has been recently planted – and when I say recently, I mean in the last 3 years, but particularly so if it’s been planted in the last year.
When trees are planted out of containers or moved, they can experience ‘transplant shock’. The roots are adjusting to a totally new environment. This is common in many trees and plants, and pines are no exception.
If your pine tree has transplant shock, it’ll look similar to a pine tree that’s not getting enough water – the needles can appear brittle or scorched, becoming pale, browning at the tips. This is often most noticeable in the outermost (newest) needles, which are most sensitive to shock. It might also be more apparent in the upper half of the tree.
Remember that pine needles should only fall from the inner parts of the branches between late summer and late autumn.
How to treat and prevent transplant shock in pines
Transplant shock will be less likely to occur if you plant the healthiest-looking pine tree in the nursery to begin with – a sign of a well-established root system.
Secondly, pay attention to the planting instruction label for that particular cultivar – ensure you’re planting in the right hardiness zone and that you’ll be able to meet its needs in terms of required soil type, for example.
Most importantly, watering new pine trees regularly – weekly at first – is the best way of preventing and treating transplant shock. If you do this, it’s unlikely that the tree will lose enough needles to prevent it from surviving until next year, when it will have had more time to adjust to its new environment.
You can actually buy conifer anti-desiccant spray, that when sprayed over the needles, reduces the amount of water-loss via transpiration. This is useful in particular for smaller trees that you can easily get good access to. If you buy this stuff though, make sure you follow the manufacturer’s instructions.
Diseases and pests causing pine needle drop
If your pine tree’s losing needles because of a disease, there will be clues that you can gather by looking at the needles and the tree’s bark. Unfortunately, there are numerous fungal and mite issues that can cause needle loss.
Here are the most common ones that you need to watch out for.
Pine needle cast diseases
These are fungal ailments, usually caused by three different fungi, Cyclaneusma minus, Lophodermium seditiosum, and Ploioderma lethale. They rarely cause tree death, but can make your tree look pretty sick and grow poorly if they’re making the tree lose needles year after year.
Needle cast disease are found in pine trees worldwide.
They can cause needle drop from any part of the tree, but the giveaway is when you see needles becoming discolored and falling from parts other than the inner branches, especially with irregular needle discoloration (see below) and outside of the normal needle-drop period of late summer to late autumn.
To detect pine needle cast diseases you’ll need to look at some of the discolored or recently fallen needles up close.
Telling the three fungi apart will often need laboratory analysis, but this is the world of hands-on gardening where we don’t all have ready access to horticultural labs! The needles you’ll typically see at least one of the following:
- yellow or black bands
- black spots
- a mottled appearance
Pine trees are most prone to fungal infections when the needles are cool and wet.
If your pine tree shows signs of needle cast disease, here are the steps you can take.
- If it’s a recent pine tree or one you aren’t attached to, consider removing the tree entirely. Fungal infections can be difficult to eradicate, and all the while they can be a source of spread to other trees – especially other pines.
- Prune out infected portions with clean pruners – you should clean them in between cuts with alcohol gel or rubbing alcohol, to avoid spreading the infection from cut to cut. Burn any pruned parts, or dispose of them in the trash.
- Avoid planting a lot of other trees close to your pine, or several pines close together – the tree needs good airflow around its needles to keep them dry
- Rake up and remove fallen needles, which can act as spore reservoirs.
- When watering your pine, try to prevent the needles from getting wet – if you need to use a sprinkler, consider watering the tree in the morning, so the sun can dry the needles out later in the day
- Copper-based fungicides can be used. They’re usually applied a couple of times a year, but you have to get the timing right – basically, you must follow the manufacturer’s instructions.
Dothistroma needle blight (fungal)
Another fungal infection that is widespread globally, this one’s more distinct in that you’ll usually notice an abrupt change in color midway along the affected needles, from green near the base to brown at the tips. Sometimes at the easliest stage you can see a brown band halfway along the needle.
It usually affects the bottom 8 feet or so of the tree, and spares the upper branches. It can be deadly to pines after several years of repeated infections.
The needles will eventually go completely brown, and fall off.
Management of dothistroma needle blight is as for pine needle cast diseases above.
Cytospora canker disease
Another fungal disease, it’s also found worldwide, particularly in the northern hemisphere and is caused by various Cytospora species.
It induces similar browning and needle loss of outer needles, BUT also causes cankers – seeping wounds in the bark – which can lead to dieback of complete branches and all the needles on them. Usually the needles are brown or reddish-brown through summer and autumn and fall off in the winter months.
Inspect the bark on the trunk and leaves of your pine. Can you see any sunken, dark or discolored areas on the bark? Look for seeping resin, which when crystallized can be whitish.
Management of cytospora canker disease is as for needle cast diseases above, except that you need to prune out limbs that have visible cankers on them. Again, don’t leave any pruned parts or infected needles lying on the ground – gather them and dispose of them in the trash.
Spider mite infestation
Spider mites are arachnids that feed on pines as well as many other species, in both hemispheres. You can sometimes see thin spiderwebs over the needles when mites are present.
Needles of infested pine can develop a spotty appearance before turning brown and falling off.
The easy way to diagnose pine mite infestation is to take a piece of white paper or card outside! Hold it underneath a branch and shake it. You’ll see tiny brownish or green crawling critters on the page.
Spider mite infestation isn’t usually lethal, but can reduce your tree’s vigor and prevent if from growing well. You can help your tree by:
- Giving it a regular hard spray with a hose to literally blast away those mites. Beware though – wet needles are predisposed to the fungal ailments above! Do this weekly, in the morning time, so the sun can dry the needles out later.
- Spraying miticides, such as those containing kelthane. These work fairly well, but again, follow the manufacturer’s instructions at all costs!
Tree diseases and pest infestations can be tricky to eradicate without the help of a trained arborist. I’d recommend consulting with one unless you’re very confident in your own abilities!
How to tell if your pine tree is dying
Dying pine trees will usually have seen a majority of its needles turn brown or fall off. Using a sharp, clean knife, make a small nick in one of the branches. If you see green tissue, the tree’s still alive, but if it’s all brown and dry, that part of the tree has died.
Needle drop due to weedkiller
Sometimes pine roots travel farther than people think, and can absorb weed killer that’s been innocently applied nearby, for example along a driveway or border. Have you put down any herbicides in recent months… and was it close to your pine tree?
If this has happened, keep the tree well-watered and hope for the best – it’ll usually survive it.
Should I rake up pine needles?
As a general rule, unless they’ve fallen as a result of disease, pine needles should be left on the ground. They make an excellent organic mulch, slowly decomposing and returning organic matter to the soil while enabling water penetration and insulating the roots from temperature extremes.
Dropping pine tree needles – a summary
If the falling needles are all coming from the inner part of the tree and are falling off between late summer and late autumn, it’s probably normal, provided it’s no more than about one-third of the total needle mass.
Otherwise, pine needles may fall because of:
- Insufficient watering
- Recent transplanting
- Winter injury
- Fungal infection – needle cast or needle blight
- Mite infestation.
Each of these problems has its own set of solutions!
I truly hope you found this article helpful. Check out some of my recent blog posts for more practical info!
USDA Forest Service – North Central Research Station Archive, CC BY 3.0 US https://creativecommons.org/licenses/by/3.0/us/deed.en, via Wikimedia Commons
Petr Kapitola from CzechiaCentral Institute for Supervising and Testing in Agriculture, CC BY 3.0 US https://creativecommons.org/licenses/by/3.0/us/deed.en, via Wikimedia Commons