Japanese yews turning brown

0612hggardendadvice1.jpg

Root rot is typically fatal to trees, but as long as the foliage remains green the tree can remain in place.

(Photo courtesy of the LSU AgCenter)

QUESTION: I have a question about Japanese yews. There are 12 yews about 8-feet tall planted about 4 feet apart in a circular pattern in about a 15-foot diameter. This is a long established garden. But this year a problem has developed. Of the 12 yews, three have turned almost completely brown. The care for the yews has not changed. The concern is the loss of these beautiful trees and the problem spreading to the healthy trees. Can the brown yews return to their prior green growth? Thank you. –Gordon

ANSWER: This is almost certainly Phytophthora root rot, a disease that attacks the roots. As the roots are killed, the top is deprived of water and turns brown, often a section at a time.

Root rot diseases are encouraged to attack plant roots when the soil stays moist to wet for extended periods. Last year was one of the wettest on record in southeast Louisiana. Even well-established plants that had been growing for years were affected. Japanese yews (Podocarpus macrophyllus) are prone to Phytophthora root rot when soils stay wet, and apparently a few of the plants succumbed to this disease. There is not a problem with the location, growing conditions or drainage; the yews did well there for a long time. This was an issue caused by nature.

Root rot is generally fatal, so I’m not optimistic about the plants that have turned brown. But as long as there is green foliage and they are alive, they can be left in place to see what will happen.

If you would like to drench the soil around the healthy yews to reduce the chances the Phytophthora will attack them, I’d recommend Monterey Agri-Fos. If you don’t see it at your local nursery, you can order it online. This will not cure a plant that is already infected, but may help prevent the spread.

*****

Love to read about gorgeous gardens? Sign up for NOLA.com’s weekly home and garden newsletter, and you’ll get Dan Gill’s latest tips as well as stories about gorgeous local landscapes. It’s easy and free. Just click here. And while you’re at it, head over to the NOLA.com’s New Orleans Homes and Gardens page on Facebook.

Japanese yew

Size and form

Plants range from 40 feet high trees to 10 feet high shrubs.
Habit is erect to broadly narrow to wide-spreading, depending upon the cultivar.

Tree & Plant Care

Yews grow in full sun to dense shade, but best with some shade to provide winter protection from strong winds.
Prefer moist, well-drained soil rich in organic matter. Yews will not tolerate wet soil.
Shallow roots benefit with a layer of mulch to moderate soil temperatures and conserve moisture.
Water well in fall before the ground freezes.

Disease, pests, and problems

More tolerant of windy sites than other yews, but drying winds and reflecting sun can cause desiccation and winter browning.
Root rots in wet soil conditions.
Black vine weevil and scale can be a problem on stressed plants.
Deer can be a problem.

Native geographic location and habitat

Japan, Korea, China

Attracts birds, pollinators, or wildlife

Cardinal, waxwing, thrushes and many other birds are attracted to the plant’s fruit and use the plant as a nesting site and shelter.

Bark color and texture

Older plants have reddish-brown bark, exfoliating in patches.
The leaves, bark, and seeds of all yew are poisonous.

Leaf or needle arrangement, size, shape, and texture

Short-stalked, 1-inch long, glossy, dark green leaves.
The leaves of all yew are poisonous.

Flower arrangement, shape, and size

Dioecious, male flowers are tiny, globose strobli in axils of leaves.
Female strobili (cone-like) solitary, green in leaf axils

Fruit, cone, nut, and seed descriptions

Fleshy red fruit (arils) resemble berries, ripening in August-November

CAUTION: The leaves, bark, and seeds of all yew are poisonous.

Cultivars and their differences

Captain yew (Taxus cuspidata ‘Fastigiata’): 8 to 10 feet high and 4 to 5 feet wide ; pyramidal shape; grows larger and more open if left unpruned.

Upright yew (Taxus cuspidata ‘Capitata’): 25 to 30 feet high; the only tree form of Japanese yew tree; dark green leaves

Problems of Yew Trees

Needles Turn Brown Branches Discolor
Soil problems – If Yews are planted in boggy areas or subjected to very wet winters and springs their needles will turn brown. This indicates that the soil is too wet for these plants and the root system is starting to die back. To minimize this problem, plant Yews on higher ground or a gently sloping site where drainage is better, or build raised beds for them.
Sometimes Yews begin to develop yellow needles on the tips of branches. This discoloration spreads, needles wilt, and the shrub dies several months later. Take a look at the roots. The bark of roots may be decayed. Research has determined that Yews do not tolerate soil that is very acid (pH 4.7 to 5.4), and this causes the environmental illness. Move affected shrubs to a location with more alkaline soil or correct the soil problem by sprinkling ground limestone on the soil over the shrub’s root system to “sweeten” the soil and increase the pH to about 6.5.
Needles Turn Yellow Branches Die
Black Vine Weevils – Black vine weevils are a serious pest of Yews. Adults are brown beetles with long snouts. They have tear-shaped, hard-shelled bodies, averaging 3/8 inch long. They feed on leaves and bark, chewing out distinctive notches along the edges of needles. Weevil larvae, white grubs with brown heads, feed on Yew roots deep in the soil. These pests are hard to spot because they feed at night, living under the bark and debris on the ground by day.
Because these weevils “play dead” when disturbed, folding their legs and dropping off plants to the ground, they can be trapped. Gently beat the branches of the infested shrub and catch the startled insects when they fall onto a cloth spread below. Apply a sticky adhesive product to the stems of the shrub to prevent the adults from climbing up and eating the leaves.
Cottony Tufts on Foliage and Stems
Mealybugs – Mealybugs are 3/8 inch long, oval, flattened, covered with white waxy powder and adorned with short, soft spines around their sides. A heavy infestation will cover the trunk and branches of Yews, the young having over wintered in bark crevices. After hatching in late May, they crawl up the trunk to the leaves, where they suck plant sap by attacking Yew foliage. Sometimes root mealybugs feed on Yew roots. The characteristic cottony tufts where needles join branches are their egg sacs. Severely infested plants tend to look unsightly, do not grow well, and may die. Honeydew secretions from the insects’ feeding encourage mold growth on foliage and attract ants and fungi.
Needles Disfigured
Scale Insects – Several types of scale insects infest Yews. Some scale pests appear as somewhat convex reddish brown soft bumps on the needles where they join the stems. The first sign of a scale attack is often discoloration of the upper leaf surface, followed by leaf drop, reduced growth, and stunted plants. Upon close inspection telltale bumps are visible. Some species excrete honeydew, which coats foliage and encourages ants and sooty mold growth. Heavy infestations of this pest kill plants.

Have you recently noticed brown patches on your evergreen trees or hedges? We’ve seen a lot of this damage recently, especially in the Staffordshire and Cheshire area.

Close-up of Yew needles showing damage

Don’t panic, don’t prune, just keep on reading…

The reason for most of this damage can be seen best where you have a hedge which is exposed at the top and protected lower down. The brown areas of damage are concentrated at the top…this is where it’s been hit by intense fluctuations in both temperature and winds.

Common Yew showing frost damage/wind scorch

You may not remember much about the weather before ‘The Beast from the East’ arrived in March?

According to the Met Office’s Summaries, both January and February had some rather pleasant spells. This was good growing weather and evergreen trees and hedges responded with new shoots. On the 26th February, I was standing in a field in Devon, admiring some trees, whilst wearing a t-shirt and shorts. Two days later, there was a minimum temperature of -11.7 °C in nearby Hampshire, bitterly cold winds hitting us from north-west Russia and snow over much of the country!

All of those lovely new buds and shoots, plump with potential and ready to burst into growth, suddenly got hit with the worst possible conditions. Below zero temperatures during both day and night accompanied by freezing winds and frosts. All that young growth began to wilt and shrivel.

Add to this the recent spell of dry, very hot weather and you suddenly start to see the damage.

But don’t despair…have a little patience, and the evergreens will do what they’re best at – continuous growth and repair. The brown needles and shoots will be shed and behind them will come new growth. It may take a while, but your trees and hedges should be able to recover.

Don’t be tempted to prune it out or ask someone to do it for you. Those plants are under enough stress at the moment! The main thing to remember is that most conifers will not grow back from old wood. So if you prune them now, you could cut back too far and the plant will never recover. If you really want to give nature a helping hand, you could consider applying a general purpose fertiliser. If you’re not sure which one to get, look for one that specifically mentions conifers or evergreens on the packaging (and make sure you follow the instructions for applying it – too much can cause other problems!)

Just a note for anyone who has damage at the base of their hedges rather than at the top (especially alongside roads or footpaths):

Remember all of the roadsalt, grit and anti-freeze that was thrown around during March’s snowy conditions? It will have been shovelled and splashed by traffic onto the base of your hedge! Excess salt kills all plants – with the obvious exceptions of marine plants like seaweeds!

If the base of your hedge, whether it’s evergreen or not, is looking unhealthy or not coming into bud yet, it may have been damaged by salt and/or anti-freeze. The same goes for roadside trees, especially if they are young or recently planted. Salt damage on trees often shows up as leaves turning brown from the lowest branches working upwards. But if the tree hasn’t come into full leaf yet, this can be difficult to check?!

If you suspect that your hedge or tree has been damaged by salt, the only thing you can do is water it thoroughly, especially in periods of dry weather. This may help to wash the salt into the lower region of the soil where the trees roots won’t have access to it.

If you have any concerns regarding the health of any of your trees, give us a call and we’ll be happy to talk to you: Get in touch

Common Problems on Yews

We have recently received several samples in the Plant Disease Clinic from yews that are turning brown. Yews are typically very hardy plants, and are not susceptible to many diseases. However, several stress factors can cause yews to turn brown.

Yews don’t like “wet feet” and can develop root problems if their roots are kept too wet. Although considered relatively drought-tolerant, too little water can also cause problems. Choosing an appropriate, well-drained site for the yew and watering during very dry periods is the best defense against these problems.

Winter damage also can affect yews. Winter injury occurs as a result of rapidly changing temperatures during the winter, bright sunshine, and inadequate water reserves in the root system of the plant. Plants usually show the first symptoms of winter injury in late winter through spring, and browning is most pronounced on the south and west sides of the plants. Although foliage turns brown, if buds remain green and viable, the plant may recover as the spring progresses.

Yews are quite sensitive to deicing salts used on roadways and sidewalks. Plants that have been affected by these salts typically turn brown starting from the side closest the area salted. Symptoms usually first appear in the spring. When salts have washed into the soil under a yew, leaching the soil with a large amount of water may help.

Wounds to the bark of branches can also cause portions of yews to turn brown. Such wounds can be caused by animals or inadvertent injury by people. Yews are not very tolerant of wounding. To diagnose this injury, the base of the plant must be examined carefully.

When yews turn brown, their site and recent history should be reviewed to determine a cause. Yews affected by salts or winter damage may recover over time, and it is wise to not prune out the brown tissue immediately in case the branch tips are still viable. When planted in a proper site and cared for, yews can be a valuable addition to the landscape.

Browning of yews, possibly from salt damage.

Leave a Reply

Your email address will not be published. Required fields are marked *