An ailing giant sequoia is a distressing thing to see! Young sequoias have vast potential – they’re the biggest trees on earth – while old ones are treasured specimens.
Almost always, the first clue that a giant sequoia’s struggling is that part of it starts turning brown – but tree owners often aren’t sure how to diagnose the issue, let alone how to revive the tree.
Giant sequoias that turn brown or appear to be dying are most often drought-stressed. Similar changes can occur following transplanting or winter desiccation. Stressed sequoia trees are more susceptible to pests and diseases, such as bark beetle infestation. Careful inspection can reveal the cause.
I hope to bring all my experience and study (I’ve read a lot of the scientific research on giant sequoias too) to make a very straightforward guide for you. I love trees, and want to see all these giants thriving.
By the time you read this article, you’ll be able to identify your problem and know the best steps to take.
REDWOOD NAMES EXPLAINED
Redwoods have three genera (categories), there’s only one type species (type) of tree that survives in each category! The genera are Sequoiadendron, Sequoia and Metasequoia.
Giant sequoia has the scientific name Sequoiadendron giganteum. It’s also known as Sierra redwood, giant redwood or California redwood, mammoth tree or Wellingtonia. Note that it isn’t even of the genus Sequoia, but Sequoiadendron! Is has scaly foliage rather than needles.
Coast redwood – Sequoia sempervirens – the only surviving species of the Sequoia genus. Giant sequoia’s the largest tree in the world overall, but coast redwood’s the tallest (tallest over 380 feet).
Dawn redwood, Metasequoia glyptostroboides, is interestingly a deciduous conifer – it goes completely brown and drops its needles every fall!
How to tell if a giant sequoia tree is dying
The simplest way to tell if your giant sequoia’s dying is by the amount of foliage that has turned brown. In this tree, needles often turn a yellow or orange shade before they go brown.
If the tree’s gone completely brown, it’s certainly dying – these needles won’t become green again, and no green foliage means no photosynthesis.
But you may well have a giant sequoia that is partially brown. Can it be saved? Often, yes it can!
Here’s how to narrow it down – you need to diagnose the problem first:
Which part of the giant sequoia tree is brown
Brown needles on the innermost part of the giant sequoia can be normal, particularly on the lowest branches. All evergreens (despite the name) eventually shed their oldest foliage, which also tends to be closer to the tree’s trunk, and low down. These are shaded from the sun and less able to photosynthesize, so are shed while the newer, outer needles are preserved. Older giant sequoias will even shed whole branches that are shaded out – that’s how in forests their trunk ends up bare at the base, while the leaves are all much higher up.
As a general rule, if leaves at the ends of some of the branches are turning brown, something’s wrong. If this is only affecting a minority of the tree’s branches, there’s a good chance you can save it.
If one side of the tree is brown (or more brown than the other), that’s often related to winter desiccation – is it brown on the wind-exposed side? I’ll unpack that below..
If the top of your giant sequoia’s going brown but the base seems intact, this may be a disease problem such as fungal infection or root rot. Depending on the diagnosis, the tree may be saveable (see ‘pests and diseases’ section below).
If the bottom half of the tree’s turning brown but the top is still a healthy green, this may be caused by lack of water. You may be able to rescue it with an irrigation regime (see below).
If only certain branches have turned brown or are dropping foliage, but others remain intact, this may be a canker disease (check the bark on that branch for any oozing pits or swellings suggesting infection that’s damaging that branch.
Often two or more problems co-exist – winter injury and drought for example. These then predispose the tree to pest or disease issues.
What time of the year is the sequoia’s foliage turning brown?
Browning of the innermost needles can be observed in a healthy tree in late summer and early autumn in a healthy tree.
If you see branch tips turning brown at other times, you’ve got an issue. Read on to learn more.
First I’ll outline the major environmental causes of a giant sequoia looking sick, stressed or turning brown.
Lack of water
Many people assume that as these trees can live for more than 3000 years, giant sequoia trees can get through anything, including dry spells, but this isn’t the case. Young sequoias are particularly susceptible to drying out, but even mature giants can struggle – for example, through the infamous 2014 California drought ¹, several monster trees died.
The number one threat to your average gardener’s giant sequoia is drought. Look out for excessive browning or yellowing of needles in summer.
Solution A – a decent watering regime
OK this is a bit obvious, but still, it’s the most important thing to do correctly. There are numerous ways to do this, but the most important element is ensuring that the soil remains moist but not wet. Giant sequoias have shallow roots, so very deep watering isn’t as important. They also don’t spread out as far as other evergreens.
I recommend a 30-minute soak around the drip-line (straight down from the tips of the longest branches) once weekly during the warm months, and once monthly in dry months, as long as the ground isn’t frozen.
If you don’t have a tree watering bag, they’re the best way to do this reliably in my opinion and you’ll find most arborists recommend them. Check out the current price on Amazon (affiliate link).
Your giant sequoia’s going to be particularly at risk of drought if it’s a small seedling or in a container. During the summer you may need to water it every couple of days – check with your finger whether the soil feels dry.
Solution B – applying mulch around the tree
You’ll see many young sequoias that are totally surrounded by grass. When rainwater hits the ground, the grass drinks it up before any gets to penetrate to the poor sequoia’s roots.
Very often neglected is the critical role of mulch! Giant sequoia’s should have a 5-foot diameter and 3-4 inch deep circle of organic mulch, such as bark chippings, surrounding the trunk – mimicking the ground surface of a forest floor.
a) suppress growth of grass and weeds, which compete for water
b) allow rainwater to readily penetrate into the soil
c) insulate your giant sequoia’s roots against temperature changes
d) steadily decompose, adding organic matter to the soil – you can replenish a little each year
Just avoid piling mulch up against the trunk (leave a 2-3 inch gap so it isn’t quite touching) so you don’t predispose the trunk to rot. Otherwise, mulch away! Mulch will help the rain do a lot of the irrigating work for you.
Many mulches have artificial coloring and other chemicals. You won’t be surprised that I try to avoid these. It’s actually kind of hard to find the right stuff, so here’s a link to an organic mulch that I like on Amazon (affiliate link).
I’m just going to give a mention to excessive water. This is normally not due to overenthusiastic gardeners so much as a sequoia having been planted on poorly drained or constantly marshy soil. They don’t tolerate it well, and while they’re unlikely to die, they may grow poorly and if stressed, more of their inner foliage may turn brown in autumn than usual.
Giant sequoias are known to be susceptible to this problem (also known as winter desiccation or winter burn) in the same way as many evergreens, such as pine, spruce, Douglas-fir, cedar, yew and hemlock (click to read articles I’ve written about these trees).
Evergreens, since they keep their leaves, continue to lose water from their foliage all winter – and particularly, harsh winter winds cause excessive evaporation and dry them out even more.
The roots have to replace this water somehow or the leaves will dry out and turn a purplish-brown – and in dry winter spells, they can struggle. This is made even worse by the fact that the vast majority of giant sequoia’s roots are within 1m of the surface, making them more susceptible to freezing than the roots of many other evergreens.
Is your tree’s near a road or driveway where it gets sprayed with road salt? Salt drastically increases the chance of winter injury.
Suspect winter injury if you notice that:
- Your giant sequoia has outer leaves that turned yellow or brown in late winter or early spring
- Particularly if it’s worse on one side of the tree – possibly the wind-exposed side, or a side that’s been sprayed with road salt
How to protect your giant sequoia against winter injury
These trees are most susceptible when young, when they haven’t developed a strong network of roots that can draw up water in place of that lost to winter desiccation.
- Watering your sequoia monthly through the winter months (except avoid when the temperature’s below freezing – freezing the top layers of ground won’t help your roots access water!). This is the most important step.
- Applying mulch around your tree – scroll up to the mulch section above. It helps rainwater get to the roots, but also insulates the roots against temperature fluctuations by trapping air, reducing the risk that the ground freezes
- Using some basic wind protection when your sequoia’s young – for example, hessian, burlap or even polythene sheeting stretched between two poles on the side that the prevailing wind comes from.
- Taking extra care to protect the tree from the spray of road salt where you can.
- Anti-desiccant spray (Amazon link to the leading brand) – which you spray over the foliage – is a simple way to reduce evaporative water loss in smaller sequoias.
Winter injury isn’t usually lethal to young sequoias, but if it happens year after year, your tree may grow lopsided, or fail to reach its growth potential.
Soil, sun and sequoias
To grow well, giant sequoias really need to be growing in a spot that gets ‘full sun’, which usually means an unshaded, south-facing site (if you’re in the northern hemisphere). Seedlings can tolerate some shade, but in the forest setting, they use their vast height gain to outperform the competition and get prime access to the sunlight.
Their ideal soil is deep, well-drained (sand or loam) and acidic or neutral (pH generally 5 to 7) ².
If your giant sequoia isn’t growing well, one of the easiest things to do is to test your soil pH. I use the Rapitest soil kit to do this at home. If your soil pH is alkaline (above 7) it may explain why your sequoia’s flagging.
It’s hard to fix inadequate sun or soil type for a giant sequoia. You can add ericaceous (acidic) fertilizer for example, which will bring the pH down – but when the tree grows large it’ll no longer be practicable. Consider whether a giant sequoia is the ‘right tree for the right place’ if you have alkaline or poorly-drained soil, or if it’s growing in a shaded site.
This section’s relevant if your giant sequoia’s been moved or planted in the past 2 or 3 years, but especially if it was in the past year.
Recent digging up and moving, or moving from a container, can cause diffuse browning of a giant sequoia’s foliage that extends to the newest foliage at the branch tips. In extreme cases (particularly likely if the sequoia’s planted into dry warm soil in summer, the whole seedling can go brown and die).
It happens because of the traumatic adjustment of the root system as it’s taken from one environment (often with the severing or damage of many roots) and placed in another environment. It can take a while for the roots to start taking up water properly again.
If you’ve recently moved or planted your sequoia, once again, it’s down to frequent watering. It’ll need at least weekly irrigation during the warm months, then monthly over the cool months. And once again, apply plenty of mulch under the tree to help water penetrate, and to suppress weeds and grass that compete for it.
An interesting case of giant sequoia transplanting occurred in Idaho in 2017, when a 100-year-old, ten-story tall giant sequoia was relocated! Keeping the roots from drying out was essential.
Interestingly, you can see that this tree’s received a little winter desiccation on one side.
Giant sequoia pests and disease
Sequoias are naturally fairly hardy to infectious diseases and pests ³. The environmental stressors outlined above are the most common causes for giant sequoias to look sick or turn brown. But there are some pests and diseases that are worth knowing about – especially if your tree’s getting a) plenty of sunlight and water b) is on well-drained soil, c) not displaying winter desiccation signs and c) hasn’t been recently transplanted.
But bear in mind – stressed sequoias (particularly drought-stressed ones) are more susceptible to diseases and pests. Sequoias planted outside of their natural range (i.e. the groves of California’s forests) are more susceptible as well.
Which diseases and pests do you really need to watch out for?
- Armillaria (honey fungus) and Heterobasidion (butt rot, Fomes rot) can lead to decay of the lower trunk of mature sequoia trees, particularly where soil isn’t well drained. You may see clumps of yellowish mushroom or white growths in the bark.
- Botryosphaeria canker is a reasonable common fungal illness that can cause cankers in giant sequoias. Cankers are wounds in bark that can look swollen or sunken, that often ooze resin. The disruption to the cambium (just under the bark) will usually cause a tree to have individual branches that are totally brown and undergo dieback, while other parts of the tree remain unaffected.
- Phloeosinus bark beetles killed numerous giant (and I mean really giant) sequoias that had already been weakened by fire and drought in the first half of the 2010s, during an infamous dry spell in California. Bark beetles (or their corresponding larvae) can be identified on the bark of weakened giant sequoia. When pieces of bark are peeled off, a characteristic ‘maze’ pattern of burrows can be seen.
So make sure you inspect your giant sequoia for any fungus-like growth around the lower trunk, any cankers on branches (especially if they’ve entirely turned brown), and any peeling bark and signs of grubs or beetles. But diagnosing these infestations isn’t easy, and treating them can be even harder. Since giant sequoia are such an important tree to preserve, I recommend having an arborist inspect your tree – they can come up with a treatment program that’ll give you the best survival odds.
How to fertilize a giant sequoia
Can fertilizer help? Generally yes, provided you stick to the manufacturer’s instructions and don’t overuse it, today’s fertilizers can help a tree grow vigorously and fend off stress and disease.
I would recommend a slow-release evergreen fertilizer – the absolute best choice for a giant sequoia in my opinion is Jobe’s Evergreen Tree Fertilizer Spikes, which you insert into the ground around your sequoia. They provide a balance of the three key tree nutrients – nitrogen, phosphorus and potassium (N, P and K). They’re truly slow-release and you don’t get the same run-off problems as with spreadable fertilizer types.
How to save a dying giant sequoia
In summary, if your sequoia’s sick, dying or brown:
- Closely inspect which parts of the tree are browning (top, bottom, one side, inner needles, outer needles) and take note of the time of year. Use the guide above to narrow it down.
- Inspect it for cankers, beetles, and trunk fungus
- Consider whether your tree has good conditions in the first place – acidic, non-marshy soil on a sunny site.
- Get a regular watering regime on the go – weekly in warmer months, monthly in cooler months
- Protect it from winter injury – wind and salt exposure – and keep a good layer of mulch under the tree
- Use a slow-release fertilizer – but stick to the instructions and don’t overuse it
I hope you enjoyed this article!
Giant sequoias can live for thousands of years – but do they die of ‘old age’? In theory, could they go on living forever? I wrote an article to finally answer this question. Check it out!
Will your sequoia get too big? How much bigger will it be in 5, or 10 years? Check out this article below (which has an interesting video…)
- Stephenson NL, Das AJ, Ampersee NJ, Cahill KG, Caprio AC, Sanders JE, Williams AP. Patterns and correlates of giant sequoia foliage dieback during California’s 2012–2016 hotter drought. Forest ecology and management. 2018 Jul 1;419:268-78.
- Weatherspoon CP. Sequoiadendron giganteum (Lindl.) Buchholz Giant Sequoia. Silvics of North America. 1990;1:552-62.
- Parmeter J. Diseases and insects of giant sequoia. InIn: Weatherspoon, C. Phillip; Iwamoto, Y. Robert; Piirto, Douglas D., technical coordinators. Proceedings of the workshop on management of giant sequoia; May 24-25, 1985; Reedley, California. Gen. Tech. Rep. PSW-GTR-95. Berkeley, CA: Pacific Southwest Forest and Range Experiment Station, Forest Service, US Department of Agriculture: p. 11-13 1986 (Vol. 95).
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Photo by David J. Stang, CC BY-SA 4.0 https://creativecommons.org/licenses/by-sa/4.0, via Wikimedia Commons
Michel Langeveld, CC BY-SA 4.0 https://creativecommons.org/licenses/by-sa/4.0, via Wikimedia Commons
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