Dying or sick holly trees – easy diagnosis and revival (a straightforward guide)

Curled holly tree leaves

Hollies are deservedly popular in home landscapes due to their beauty and hardiness. But when you own a holly tree or two, things don’t always grow to plan (terrible pun there). They’re prone to leaf discoloration and spotting, can grow poorly and even defoliate completely – and it can be hard to tell what’s going on.

Holly trees that are sick, dying or stressed will display excessive numbers of yellow leaves and undergo leaf drop. Typically this results from drought, poor drainage, excessive shade or iron deficiency. Pest infestation and diseases such as Phytophthora root rot can cause similar symptoms.

I’ve been around holly trees my whole life and I’ve always been fascinated by them. What I’d like to do is share all my experience, research and learning with you, and make it easy for you to find out what’s going on with your holly and revive it!

Which holly species are we talking about? This article will help you with:

and practically all other holly species and hybrids.

My holly tree has yellow leaves

Most holly tree species are evergreen, but that doesn’t mean they keep their leaves forever. Rather, instead of losing all their leaves each autumn, they shed a few each year.

Normally, a few older holly leaves will turn yellow or brown around spring or early summer each year, and fall off. These leaves are closer to the center of the trunk and are typically a year old.

If new growth is appearing in the few weeks after the yellow leaves fall, it’s a good sign that your tree’s going to make it.

However, stressed hollies will lose more than the normal few each year.

You have a problem if the leaves are turning yellow or brown in (a) winter, summer or autumn, (b) in excessive amounts, (c) when it’s happening to the new leaves at the outer parts of branches.

Causes of yellow leaves on a holly tree

If it isn’t natural leaf yellowing as above, it’s likely to be one of the following causes

  1. Poor drainage. Check for puddles over the roots. Hollies (especially Japanese holly) don’t like ‘wet feet’ – few evergreens do. If the soil isn’t well drained, the roots are drowned in standing water, leading to excessive leaf yellowing and drop.
  2. Drought. On the other hand, the soil needs at least some moisture. Consider this if you’re seeing yellow leaves in summer. Homeowners tend to regard holly as a robust tree and focus on watering the flowerbeds. It benefits from a good soak weekly in summer months, and monthly the rest of the year.
  3. Too much shade. Hollies usually need direct sunlight at least part of the day. If it’s fully shaded out by your home, a fence or other trees, prematurely and excessively yellow leaves will appear as a sign of stress.

Holly trees, chlorosis and iron deficiency

Much is said in books about holly tree chlorosis (yellow leaves due to lack of chlorophyll) and iron deficiency. This problem is exacerbated by alkaline (pH >7) soils The idea is that trees have a harder time taking up iron when the pH is high, so it helps to either

  • add lots of iron to the soil to compensate, or
  • to try to acidify the soil so that the iron that’s there is taken up better
  • (or both)

While iron deficiency certainly does cause chlorosis in hollies, that doesn’t mean all yellow holly leaves are caused by iron deficiency. In my opinion, it’s more likely that the problem’s caused by over or underwatering, which are much more common issues.

While there’s no easy method to test your soil’s iron levels, at the very least you should know your soil’s pH. Most trees and plants have a preferred pH to grow in and it’s foundational knowledge for any gardener.

Personally, I use the Rapitest home soil test kit (which, as well as the pH, can tell you about your soil’s levels of nitrogen, phosphate and potassium – see affiliate link). I use the Rapitest electric meter (affiliate link) as well for quick readings on different parts of my property. Quick and accurate.

You can lower your soil’s pH (make it more acidic) by adding elemental sulfur, which is available online and from most good nurseries. Alternatively, to boost the iron content, you can buy chelated iron. I wouldn’t apply both of these, as there’s a chance you’ll overdo it. BUT, if ferrous sulfate’s feed’s available, consider using that – it contains both iron and sulfur – here’s an affiliate link to the right stuff. Just make sure that you follow the manufacturer’s instructions in all cases!!

Holly and transplant stress

If your holly tree was planted or moved in the past year, it’s likely that stunted growth, excessive leaf yellowing or a sickly appearance are caused by ‘transplant stress’. This occurs when the roots are suddenly flung into a new environment (often undergoing some damage in the planting process) with different nutrient, pH and moisture levels.

It can take many months for the roots to adjust, and in this time they struggle to take up enough water. As a protective response, the holly will allow some leaves to drop, reducing the surface area from which the tree loses water. In its most extreme form, this is called ‘transplant shock’, and the holly can lose almost all of its leaves!

The best way to protect and treat a recently transplanted holly is to water it frequently to help the struggling roots. This usually means a deep soaking with a hose once weekly in summer, and monthly throughout the rest of the year. Hollies usually recover from transplant shock as long as the roots aren’t allowed to dry out (particularly the English holly, Ilex aquifolium, has great powers of recovery).

Transplant stress symptoms are more common when hollies are planted in the summer, when many gardeners and landscapers roll their sleeves up. It’s much better to plant in the autumn or winter, to give the roots a chance to establish before the next summer growing season.

Yellow holly leaves with spots

holly leaves yellow or brown spots

Why do holly leaves often become spotty after they turn yellow or brown?

Yellow leaves, which are soon going to be shed, are in a weakened state, which makes them susceptible to fungal infections from a range of different fungi.

This is quite normal, and as long as the greener holly leaves aren’t getting spots as well, it’s of little consequence.

Holly leaf ‘scorch’

‘Scorch’ refers to brown, withered tips or edges of otherwise green leaves.

It happens when the leaves are losing more moisture to the air than the roots can replace. This is caused by either simple drought (the roots don’t have enough water) or by excessive wind exposure.

In the heat of the summer, hollies that don’t get enough water can’t keep their leaves turgid, so the tips wither.

But in winter it can be even worse. Being evergreen, water evaporates from the leaves all year round – particularly in strong winds – and this puts more demand on the roots to draw up water to replace it and prevent scorching. And roots certainly do dry out in winter during drier weeks.

The problem’s much worse when the ground freezes and roots temporarily can’t absorb any water.

Leaf scorch in winter is sometimes called winter burn, windburn or winter injury.

How to prevent holly leaf scorch

Luckily some basic practices will get your holly tree looking healthy again.

  • Water your holly tree(s)! A 15-minute soak once a week in summer, reducing to monthly over winter, will give the roots enough water to replace that which is being lost via the leaves (alternatively, a bucket or two of water for each small bush daily in summer, and weekly in winter is a sustainable practice). You can skip if there’s heavy rainfall or if you see standing water around your holly tree.
  • Apply mulch, such as organic bark chippings over the roots. Almost every tree benefits from this! Mulch suppresses weeds and grass which compete for water, helps rainfall permeate down into the soil, adds organic matter to the soil as it decomposes, and it looks good! A 2-3 inch thick layer will do, but keep it from touching the trunk, where it can contribute to rot.
  • Consider some basic wind protection. This is needed most over winter. You can stretch windbreak netting between two posts, or even wrap the bush in hessian or sheet plastic (but it doesn’t look so good). Wind protection’s particularly important for young holly hedges.

Common pest and disease problems of holly

holly ilex black tar spot

Holly leaves with black spots

‘Tar spot’ is caused by Macroderma curtisii, a fungus. It tends to affect English and American hollies. Yellow spots appear on the leaves in late spring, turning brown over summer and then black by autumn.

The disease is unsightly, but doesn’t affect the health of your holly much. If it bothers you, you can cut off infected leaves (don’t leave them on the ground where fungal spores can spread back onto the tree – dispose of them).

Thinning out your holly tree can improve airflow and reduce the amount of tar spots next year.

Holly leaves with yellow, brown or purple blotches

Phytomyza ilicis, holly leaf miner
Phytomyza ilicis, holly leaf miner, causing yellow and brown blotches on the leaves

Holly leaf miner is a common pest. It’s a tiny fly, whose larvae burrow through holly leaves causing distortion to the leaf shape and unsightly blotches on the upper surfaces.

There are two main types of miner insect, causing similar symptoms. Phytomyza ilicicola feeds on American holly (Ilex opaca) and Japanese holly (Ilex crenata), while Phytomyza ilicis targets English holly (Ilex aquifolium).

It’s very unlikely that a holly leaf miner infestation will cause significant damage to your holly or prevent it from thriving. Some regard this as part of the natural biodiversity of holly trees. It’s likely only to annoy you if you want some pristine holly leaves for Christmas decorations, but usually that will still be possible.

It’s possible to cut off affected leaves by hand if your holly tree is small – it might reduce the number of affected leaves next year.

Holly leaves have tiny white insects on them

Scale insects, which look like tiny immobile white, grey or brown bumps without visible legs, frequently infest holly – check the undersides of leaves in particular. These suck sap from the leaves and when lots of leaves are affected, the entire plant can begin to look stressed i.e. excessive leaves will turn yellow and drop off.

If you’re only seeing scale insects on a few leaves, you can cut these leaves off and dispose of them, or even scrape those critters off. They’re easily suffocated by spraying on horticultural oil (such as Neem oil), but it works best if you spray in early spring before the new growth starts.

Holly root rot

Phytophthora Root Rot
Phytophthora Root Rot affects many plant species – here, rhododendron

This one’s particularly problematic worldwide, AND hard to diagnose since it affects the roots. What’s more, by the time you see changes in the branches and leaves it’s too late. Usually the signs are wilting, yellowing at the tips and edges of leaves, dieback and slow growth – but often the holly dies quickly.

The only sure way to diagnose it is to look at the roots – and even then it’s tricky. Sometimes roots will have black ends or start to disintegrate.

Phytophthora root rot is probably the most significant type. It’s a particular issue in yew trees and hedges. Click here to read more (and for an informative short video).

Black root rot is a similar illness caused by a different pathogen. Here’s a very helpful and succinct video from Virginia Co-operative extension.

Root rot’s most likely to occur where there is poorly drained soil – conditions that encourage this water mold to flourish.

Phytophthora species also cause holly leaf blight, which causes purple or black spots, often along the midrib of the leaves. A clue to this diagnosis is that the spots can appear on the berries as well as the leaves. It causes dieback of entire twigs and is more common when leaves after persistent wet – so by thinning out the tree and improving airflow, you can suppress (if not totally cure) the infection.

If you think you might have root rot or Phytophthora infection, I’d consider calling in a trained arborist for a check, as this can cause significant issues for other trees or plants on your property as well as your holly and controlling them is difficult without expert help.

Is it better to cut off dying leaves?

Once a holly leaf has turned yellow or brown, it isn’t going to turn green again and will eventually fall off by itself. I wouldn’t worry about cutting them off by hand, though certainly it wouldn’t cause any harm to the tree.

If the dying leaves are covered in spots (from the fungi that opportunistically grow on weakened foliage), cutting off and disposing of the leaves will mean fewer spores will be released to affect other leaves or plants – so go for it if you have the time. But be careful – pruners themselves can spread infection around, so wipe them in between cuts with rubbing alcohol or >70% alcohol hand sanitizer.

Should I fertilize holly bushes?

Yup – most holly trees, particularly when young, will benefit from the addition of a ‘complete’ fertilizer – one that contains the three main plant nutrients (nitrogen, phosphate and potassium, i.e. N, P and K).

Those that come in a granular slow-release form are best for most gardeners – it’s more difficult to overdo it (‘fertilizer burn’ is another leaf problem so be sure to follow the manufacturer’s instructions!) and they’re simple to use.

Miracle-Gro All Purpose continuous-release plant food (affiliate link ) is the stuff I recommend for holly.

How can you tell if a holly tree is dying?

Most hollies, particularly English holly (Ilex aquifolium) are tough to kill off, but you might get some individual dead branches in a stressed tree. Using your fingernail or a sharp knife, make a nick in the branch. If it’s moist and green under the surface, it’s alive, and if it’s dry and brown, it’s already dead.

Any holly that isn’t dead yet is worth a revival attempt!

How to revive a sick holly bush – a summary

  • As long as the soil doesn’t seem drenched, give it a good watering regularly – weekly during the summer and monthly for the rest of the year.
  • Cover the roots with mulch 2-3 inches thick, keeping it from touching the actual trunk
  • Erect wind protection if it’s on an exposed site (particularly if young)
  • Test the pH and if alkaline (>7) consider acidifying the soil or adding iron (see above)
  • Otherwise, apply a complete slow-release granular fertilizer in accordance with the manufacturer’s instructions
  • Check the leaves (top and bottom) for scale insects – remove these leaves or use horticultural oil
  • If it continues to decline, it may be Phytophthora root rot, and need to be removed

Image attributions:

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

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

Photo by David J. Stang, CC BY-SA 4.0 https://creativecommons.org/licenses/by-sa/4.0, via Wikimedia Commons

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

gailhampshire, CC BY 2.0 https://creativecommons.org/licenses/by/2.0, via Wikimedia Commons

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