Dying, sick or brown yews: how to diagnose and rejuvenate easily


yew tree with brown dying needles

The yew tree has a historical and mythical connection to death. But what about when the tree itself seems to be dying? Rather than wax philosophical, let’s take a hands-on approach! How can you tell if your yew tree or hedge can be saved, and if so… how can yew do it? Sorry.

Typically, yew trees will turn brown or excessively shed needles because of poorly-drained soil, recent transplanting or winter injury, particularly when sprayed with road salt. Yew trees are particularly susceptible to phytophthora root rot and to mealybug and black vine weevil infestations.

Yew are standout trees and, with time, patience and care, can make some of the most excellent hedging that you’ll ever see. Some of the common issues can be readily helped with a little bit of effort, and I’d love to share my experience and what I’ve learned about yews, so that yours can get back to health quickly.

It’s particularly disheartening when you’re making a yew hedge, and one or two of the yews look sickly, aren’t growing well, are going brown, or losing needles!

So which trees exactly am I talking about? There are 11 species of yew, that is of the genus Taxus. The best known worldwide is Taxus baccata (known as European, Common or English yew).

In the US, while you’ll find T. baccata planted ornamentally, you’ll find some others: in the North-East and Canada you’ll see Taxus canadensis (Canada yew), Taxus floridana (Florida yew) in the south-east USA and Taxus brevifola (Pacific yew) out in the western states.

These species share much in common, and this article is designed to address common issues for all yew species – not the rarest of the rare diseases, but the ones that are genuinely common, which are probably affecting your tree!

But first…

How do you know when a yew tree is dying?

  1. Excessive needle browning or needle drop. Yew trees should only lose a proportion of their inner needles in the late spring or early summer each year – NOT the ones at the tips.
  2. A sickly pale color – especially when compared to other yew trees
  3. Not putting on new needles or height – most yews will grow a foot every year if conditions are right

And how can you tell if it’s actually dead?

Using a sharp, clean knife, make a small scratch into one of the branches. If it’s moist and green underneath, your tree’s alive. If it’s dry and brown, that part is dead. Move down to the trunk or main stem of the tree and check the same thing there.

If you can find some moist and green parts under some bark, the tree still has a functioning vascular system and you may be able to save it. Read on!

Yew trees turning brown or losing needles

Yews are evergreen, but that doesn’t mean they aren’t supposed to drop their needles. In a healthy tree, the outer needles stay green while a proportion of inner ones (which are older) go brown or yellow and drop off each year. Usually this is more pronounced around the tree base, which is shaded out more by foliage higher up.

Yews are a bit different from most other conifers in their timing. They tend to naturally drop needles in late spring and early summer, while pine, spruce and fir usually shed theirs in late summer and early autumn. This has alarmed some tree owners as they see yews shedding when other conifers are growing out.

Yew needles are said to remain on the tree for about 3 years on average. Once they fall off, either naturally or because of a tree issue, they’re unlikely to grow back.

So when is yew needle browning or shedding not normal?

  1. it’s losing a whole lot of inner needles (and left looking bare except near the tips)
  2. the needle drop is happening at times other than late spring and the first half of summer
  3. the branch tips are brown – only the inner parts should be browning
  4. the discolored needles have notches bitten out of them, or if tiny insects can be seen (indicating possible infestation)
  5. The discoloration or shedding is asymmetrical – e.g. more at one side, or at the top
  6. it’s associated with poor growth or the tree looks sickly – a clue to a bigger problem

I’ll break down these scenarios below.

What causes yew trees to turn brown, or to excessively shed needles?

It’s pretty disheartening when you see this, especially in a row of yews where the brown one sticks out like a sore thumb.

In yews, it’s usually caused by adverse conditions, and in a minority of cases, disease or pests. The two most common causes are poor soil drainage and winter injury.

Yew trees and waterlogged soil

Yews are famously intolerant of over-watering or otherwise soggy, waterlogged soil. This can particularly affect gardeners with clay soil – a hole is dug for the plant with absorbent compost, which becomes a well for surface water to drain into, occluding air and drowning the roots.

Have you been over-vigorously watering your tree – or perhaps it’s in a low spot that rainwater drains towards? The roots will become impaired, resulting normally in a generalized browning involving the branch tips – which will eventually drop off if the situation is severe.

A yew may never thrive in a naturally boggy area. You may be best starting again with a more tolerant species – other evergreen choices that come to mind would be loblolly pine or white cedar. The Canada yew is perhaps the best yew at tolerating wet soil.

Can you underwater a yew tree? Certainly. You may have more sandy soil that never becomes waterlogged. In your case, drought is the more likely cause of browning and needle loss.

You can check how wet your soil is by using a trowel near the base of the tree – dig about 2-3 inches down and feel the soil with your finger. If it feels damp, you’re good – water isn’t required. If it’s dry or the soil doesn’t stick to your skin, it needs some.

To water a yew, give it a 30-minute soak in the area under the canopy once a week during the summer, and monthly through the colder months, including winter, as long as it’s above freezing.

Yew trees and winter injury

This is a big one. I’ve written a lot about winter injury and its impacts on evergreens such as pine, spruce and cedar trees.

Since evergreen trees have their needles all winter, moisture is always evaporating from them – not from the hot sun so much, but from airflow and particularly strong winds. The roots have to be able to draw water from the ground to replace it, but the needles can lose so much that this can be a struggle. This is all the worse when the ground’s frozen.

Water loss from needles, plus not enough coming up from the roots, leads to winter injury in yews – also known as winter desiccation or winter burn.

Clues to winter injury are:

  1. Needle browning at branch tips – sometimes gradually changing from green to brown along the needles
  2. It’s worse on the side of the tree that’s exposed to the main prevailing wind
  3. It’s worse on the side that is close to a road or driveway – road salt spray greatly exacerbates winter injury
  4. It’s sometimes worse at the top of the tree that at the bottom

Yews normally recover from winter injury, but if it’s repeated year after year, this can impact its health and stunt its growth. You can prune off branches that have completely died (consider the scratch test above), but otherwise leave areas that are mildly desiccated.

How to prevent winter injury in yews

  1. Consider some basic wind protection – fencing, or for young yews, burlap, horticultural fleece, or even plastic sheeting stretched out between two posts. This can also protect against spray from road salt.
  2. Water the tree during the winter! A 30-minute soak under the canopy once a month as long as you’re above freezing, will help. Don’t do this if the ground feels waterlogged or boggy.
  3. For young yews, consider spraying on anti-desiccant, available online (affiliate link). This forms a layer on the needles which reduces evaporation through the winter. Easy!
  4. Almost all trees benefit from a 3-4 inch layer of organic mulch, such as bark chippings, over the root area. This helps water permeate through the soil and insulates it from rapid temperature drops. Just avoid piling it up against the trunk itself.

Transplant shock

This applies if you’ve planted your yew or yews in the last three years – but particularly in the past year.

When moved or planted from a pot, the tree’s roots have to suddenly adapt to a new environment. This can be stressful for the plant, resulting in sudden or excessive needle yellowing or browning, leading to shedding. This is mostly seen at branch tips, but can affect the whole tree.

I find gardeners sometimes enthusiastically plant the tree, but then don’t give it much water! Regular watering (unless the soil already seems boggy or waterlogged, as discussed above) is so important for young trees to get established and to prevent and limit ‘transplant shock’.

Bark damage

Yews aren’t forgiving of damage to their bark. If you have a yew hedge and one or two of them are brown or aren’t growing as well, inspect the base of the trunk closely for any damage – rabbits or other small mammals may have gnawed here. Interestingly, despite their well-known toxicity, deers have been observed to chew at yew trees without becoming sick, as sheep and cattle tend to.

Damage from lawnmowers and weed trimmers can have a similar appearance.

Have a look at my article on bark damage for some straightforward advice on whether the tree can survive, and what you can do about it.

Cat and dog urine

I’m not sure if there’s something about yew trees that attracts them, or if yews are particularly sensitive to urea, but I’ve noticed that this can be a problem from time to time. Keep an eye out if you can to see if your yew tree or hedge is a particularly favorite spot for your neighbor’s dog or cat to pee on.

For cats, try placing some large stones (too large for them to move with their paw) around the base of the tree. For dogs, try spreading some thorny branches, such as bramble. You can buy tree pet guards – a cage that is fitted around the trunk – that’s if you can guard your yew 24/7!

Root rot

Yews (Taxus) are known for being very susceptible to root rot caused by Phytophthora, a mold-like organism that causes them to turn yellow, wilt and exhibit poor vigor and is found worldwide. It often leads to the complete browning of the tree and eventual death.

This disease goes alongside the issues of yews growing poorly in waterlogged soil – which also encourages Phytophthora to thrive.

There’s no easy way to identify if a yew has root rot without digging it up and analyzing the roots themselves – which may be black, fragile and soft – but it should be suspected where a yew in damp soil is browning rapidly, particularly if other yews beside it seem much healthier.

Once the infection’s set in significantly, little choice here but to dig it up and start over – and you should put the tree parts in the trash, and even dispose of the topsoil as well. However, trees with mild chronic infection can be treated with approved fungicides – I’d consider calling in an arborist if you’re sentimental about your tree.

I found a tremendously informative and useful video of a plant diagnostician from the University of Kentucky observing Phytophthora root rot in a yew hedge.

https://youtu.be/d5sa7-63j-A

Mealybugs

mealybugs

In late spring and summer, have a close look at your yew around the base of the needles and at branch junctions. Can you see any insects? Mealybugs are tiny white insects with a furry appearance. You might notice a sticky secretion (or the black soot that adheres to it).

They’re a common yew pest – particularly if you have dogwood trees nearby, which can act as an alternate host for these minibeasts.

Mealybugs cause a variety of symptoms in yew – from poor growth, yellowing, to needle loss and sparse foliage.

At the most basic level, a blast with a hose will see off many of these bugs and limit their impact. Horticultural oils such as this product (Amazon affiliate link) work well, and will have minimal environmental impact.

Black vine weevil

Black vine weevil larvae grubs
Black vine weevil larvae
Black vine weevil size
Black vine weevil adult form (on a match for scale)

Black vine weevil is a common problem for yew and rhododendron (have you got any rhododendron on your property??). Suspect it if your sick yew has needles with some bites – notches – taken out of the edges; these weevils eat leaves from the edges rather than holes out of the middle. This notching appears from spring through to autumn.

The weevils are usually hard to see, as they regress during the daytime towards the base of the trunk, and emerge at night.

Black vine weevil isn’t usually lethal, but the larval stage (when the pest is feeding on the roots, rather than the leaves) can cause trees to appear stressed, yellow, and lose foliage.

If you see notching on the yew leaves, I’d consider consulting a trained arborist, as the treatment depends on the black vine weevil’s current stage in its life cycle.

Does fertilizer help a dying yew?

Yes! While established yews don’t always need fertilizer, those which are weakened can certainly pick up with a little simple fertilizer application. It’s easy to do – I usually go for Jobe’s Evergreen Fertilizer Spikes (Amazon affiliate link).

It’s slow-release, which settles any timing issues, and is a ‘complete’ fertilizer containing nitrogen, phosphorus and potassium – the three main elements whose compounds are involved in tree vitality and growth.

Just make sure you don’t use more than the manufacturer recommends. Using too much can harm the tree rather than help it.

How to rejuvenate a sick yew – a summary

The process of rejuvenating a yew tree depends on the cause of its decline, as outlined above. The most important element is prevention of recurrent damage by keeping conditions in an ideal state while the tree recovers. Here’s a summary of the main process.

  1. First establish if any browning or shedding is untimely or excessive, or within normal patterns
  2. Inspect the foliage for notching, and the branch junctions for white mealybugs
  3. Keep the soil moist with regular watering – but never allow it to become boggy or stagnant
  4. Prevent winter injury with winter watering and shield from strong winds and road salt
  5. Use slow-release fertilizer such as Jobe’s Evergreen Spikes to ensure access to the essential nutrients.

I hope you found this article helpful! Please check out some of my latest articles here.


Image attribution:

Crisco 1492, CC BY-SA 4.0 https://creativecommons.org/licenses/by-sa/4.0, via Wikimedia Commons

I, Opuntia, CC BY-SA 3.0 http://creativecommons.org/licenses/by-sa/3.0/, via Wikimedia Commons

Salix, CC BY-SA 3.0 https://creativecommons.org/licenses/by-sa/3.0, via Wikimedia Commons

Recent Posts