Why has my tree or shrub died?

Losing a tree or shrub can be distressing, especially if it was expensive, had sentimental value or was performing an important function such as screening. We consider some of the most common reasons why plants fail to help avoid a repeat in the future.

Dead Grevillea shrub

Quick facts

Common name Trees and shrubs
Botanical name Various
Areas affected Tree and shrub beds; container-grown plants
Main causes Various including poor establishment and disease
Timing Any time

How do I tell if my tree or shrub is dead?

This may seem a silly question but it is not always obvious. Deciduous trees look dead in the winter when their stems are bare of leaves, for example.

When you suspect a plant is dead but are not sure, take the following test;

  1. Scratch the bark (the “scratch test”) on the shoots of your trees or shrub with your thumb nail or a penknife. A stem with green under the bark is alive; a stem with brown under the bark is dead. Living shoots also tend to have smooth, firm bark, whereas dead or dying shoots tend to have flaking, peeling or wizened bark.
  2. Where the shoots are dead at the tips, repeat the test on thicker wood to see if that is also dead. Where most or all of the upper parts of a plant are brown under the bark, the plant is most likely dead.
  3. A final test is to scrape the bark of the main stem just below the soil line or on the roots themselves. If this appears dark in colour, especially with any sign of soft, rotting roots, then you can be confident your plant is dead.

Plants that still show some signs of life (e.g. green under the bark or a firm rootstock) could be left for a few months or until spring to see if they improve. Where they continue to deteriorate or simply fail to come into growth in the spring, assume they are dead.

Common reasons new trees or shrubs fail

It would be wonderful if every new plant we bought thrived. However, as every experienced gardener knows, sometimes new plants do sadly die. Buying from a reputable nursery that offers a 3-5 year guarantee is some safeguard but it is useful to know why a tree or shrub might have died.

Some of the reasons new plants fail can be specific to whether the plant stayed in its pot or was planted into the garden. Other causes of failure are more general.

Plants in the ground

The first two growing seasons after planting are a critical time for a tree or shrub. Unless it gets its roots successfully established into the surrounding soil, it will be prone to failure particularly in times of stress such as during drought or waterlogging.

Establishment failure. Plants that die within the first year after planting are most likely to have failed to establish. Their roots will most likely be dead or stunted. When digging the plant out look for signs of;

  • Too wet - wet season, wet soil or overwatering. Remedy: Check the soil around new plants for standing water or waterlogged conditions. Reduce watering where necessary (remember plants in the ground do not need to be watered as frequently as those in containers). Choose plants suited to wet soil conditions
  • Too dry - dry season, dry/unimproved soil or erratic/insufficient watering. Remedy: Thoroughly wet the rootball on planting; if the compost or soil repels rather than absorbs the water, add a few drops of washing-up liquid into the watering can to act as a wetting agent. In the first growing season check all new plants weekly for signs of drying, especially in dry weather. Water thoroughly (applying sufficient to wet the full depth of rootball) at the first signs of the soil drying. Choose plants suited to dry soil conditions
  • Planted too deep - causes rotting of stem base; a common failure of woody plants. Remedy: Avoid deep planting by positioning the tree or shrub with the first flare of roots (thicker roots, not the fine adventitious roots) just below the soil line. Scrape away the soil or mulch from the base of trees and shrubs suspected of deep planting
  • Undeveloped roots that have failed to grow out into the surrounding soil – caused by compacted rootball that was not trimmed or loosened (‘teased out’) on planting, a restrictive root wrapping material or compacted surrounding soil. Remedy: Trim potbound rootballs prior to planting to encourage lateral root growth. Remove root wrappings unless stated otherwise by the nursery. Plant trees and shrubs using good techniques (i.e. dig out a hole one times the depth and three times the width of the rootball) to ensure soil compaction is alleviated. In post-planting cases of suspected soil compaction, carefully loosen a ring of soil to the outer edge of the rootball using a border fork. Congested roots can be trimmed in the dormant season or spring
  • Large specimen tree or shrub - these can be more prone to failure than smaller plants, due to an imbalance in the size of the root system with the top growth. Remedy: Only plant larger specimens when there is a special requirement, such as for instant screening, and ensure they are kept well watered for several seasons after planting

Unsuited to site conditions. Some plants are not too fussy about their environment but others will suffer if given the wrong conditions. A plant in the wrong place can quickly fail. Remedy: Check before planting the preferred soil texture (well-drained, moist, etc), pH and degree of sun or shade for your tree or shrub and site it accordingly.

Rabbit, deer or rodent damage. Plants in the ground can get nibbled by wild animals. Although rabbits and deer are mostly troublesome in rural and semi-rural gardens, mice and voles can be found in all gardens. Look for patches of stripped bark on the lower sections of woody plants, especially in winter and the sudden disappearance of stems and foliage of herbaceous plants, usually in spring and summer. Remedy: Where rabbits or deer are likely to be a problem, fit all newly planted trees and shrubs with spiral guards, enclose individual plants or beds in chicken wire or choose plants that are more resistant to damage; check all new plants for mice and vole damage and clear away cover where possible.

Plants in containers

There is no inherent reason why a tree or a shrub kept in its pot should fail – after all, nurseries grow thousands of plants successfully in pots, repotting as required, sometimes for several years before offering them for sale. However, a plant in a container can be more at risk of certain problems that, if gone unnoticed, can lead to the loss of the plant;

  • Too wet – wet season/overwatering. Remedy: Bring containers into the lee of a wall if the weather is very wet and check the drainage holes are not blocked. Water when the top of the compost starts to show signs of drying, not before. Plants need less water in winter, if growth is slow, if they are not in leaf or if they are in a large container in comparison to the size of plant
  • Too dry – erratic/insufficient watering. Remedy: Check plants regularly for drying out and water if the compost feels dry and/or the pot has become lighter in weight. Plants outside in summer should be checked at least once a day
  • Overpotted – plants that are potted into too large a container, especially late in the growing season or in winter can rot off. Remedy: Only repot into the next size pot or downsize plants already overpotted
  • Frosted roots – roots can be more vulnerable to cold damage than the top growth so trees and shrubs in containers are less protected from frost than those insulated by the soil. Remedy: Wrap the sides of outdoor containerised plants with bubblewrap before winter and bring them to a more protected position such as us against a house wall
  • Vine weevil – creamy-white, c-shaped grubs of vine weevil can wreak havoc with plants in pots by eating their roots. Remedy: Check rootballs at the first sign of a problem and treat if grubs are found. Nematodes are effective for trees and shrubs in the ground

Wind, sun or cold damage

Plants that have changed environment suddenly – for example, from a polytunnel in the nursery to your garden – can suffer from physical damage, being scorched by wind, sun or cold.

Remedy: Unless you know where the plant was growing before purchasing it, harden off new plants by keeping them for a few days in a sheltered/shady spot outdoors under horticultural fleece. Remove the fleece at night but replace during the day for a further couple of days before planting out.

All plants have their limits and may be caught by extremes of weather.

Remedy: Check the growing conditions of your plant to see if it requires protection from wind, sun or cold and position or protect it as required. Fortunately, many trees and shrubs often recover from weather damage, especially if only the exposed side(s) is damaged so cut the damaged parts out and wait until the growing season to give it the benefit of the doubt.

Weak or unhealthy plant

Of course, if the plant you bought was weak or sick at the start, it is highly likely that it will continue to suffer or die in your garden.

Remedy: Inspect all new plants for signs of disease or poor health before buying. Avoid buying sickly specimens. Plants that arrive in a poor state via mail order should be returned or the supplier informed.

Common reasons well established trees or shrubs fail

Plants that have been in the ground some years, having put on growth and appeared healthy before dying are most likely to have died of a disease picked up from the soil or a major physical/environmental stress.

If the plant never thrived, see the section above on ‘Common reasons new trees or shrubs fail’.

Soil borne diseases

Plants can pick up diseases from gardens soils or other plants. While there are many weakening and unsightly diseases that cause problems for the foliage such as rusts, scabs and leaf spots, these do not usually lead to the demise of the plant. Instead, it is the root diseases that are most to blame for the loss of established plants. Most commonly encountered are;

  • Honey fungus – this can be identified by the presence of creamy-white fungal sheets (mycelium) under the bark of the base of the stem or roots of an affected plant. Remedy: Dig out the dead or dying plant and bin or burn. Avoid replacing with susceptible plants in that area
  • Phytophthora root rot – as this is a disease caused by a microscopic fungus-like organism, the only visible sign is a plant with dead or rotting roots. Test kits are available or RHS members (UK-based only) can submit samples to RHS Gardening Advice for diagnosis. Remedy: Dig out the dead or dying plant and bin or burn. Avoid replacing with susceptible plants in that area
  • Verticillium wilt – dark (black) staining can be found under the bark of shoots that have died back as a result of this infection. Remedy: Dig out the dead or dying plant and bin or burn. Avoid replacing with susceptible plants in that area

Top growth diseases or disorders

A number of specific diseases or disorders that affect the upper parts of plants (trunk, stems and leaves) can be severe enough to kill, permanently weaken or make so unsightly that removal of the affected tree or shrub is sometimes best.

Examples of such diseases or problems include;

Bacterial canker
Box blight
Bracket fungi
Escallonia leaf spot
Graft failure
Phytophthora ramorum and P. kernoviae
Robinia pseudoacacia ‘Frisia’ problems

Root disturbance or damage

Trees and shrubs that have been moved do not always re-establish successfully and some woody plants such as broom and magnolia resent root disturbance at any stage.

Remedy: If moving established trees and shrubs is necessary, move them at a favourable time of year (autumn or spring for evergreens; when not in leaf for deciduous) and ensure they are kept well watered in the subsequent growing season.

Additionally, the roots of trees and shrubs can extend far into the surrounding soil. Major disturbance such as trenching, building work, drainage work, and patio or driveway construction that damages the roots of nearby plants can lead ultimately to their death. The other main cause of damage to roots is where the soil is compacted through heavy machinery or soil levels are changes suddenly, burying part or all of a root system.

Remedy: Minimise the impact of root damage to plants during ground work, especially in the growing season. Excavating by hand can help save large roots or for more extensive work near trees use an Air Knife to remove soil without cutting through rotos. Avoid changing soil levels around established plants or lift and replant/replace where necessary.

Prolonged drought or waterlogging

Unless a plant is known to tolerate drought or wet soil conditions, extended periods of either can put plants under stress and, in some cases, lead to plant death.

Remedy: Consider watering and mulching smaller plants during extreme drought and always keep containerised plants well watered in dry weather. After a period of waterlogging or flooding, especially in the growing season, try aerating the soil and assess whether drainage or flood defences are required.

Replacing dead trees and shrubs

Whether you have been able to determine the cause of why your plant has died or not, there will come a point when you will need to remove it and replace it. It is best to err of side of caution and assume disease was involved unless there is good evidence to contrary.

What to do with a dead plant

Dead plants are best removed, to minimise possible sources of infection to neighbouring plants and to create space for replanting. Aim to;

  • Dig out the plant and as much of the stump and thicker roots as possible, using a stump grinder for larger stumps
  • Bag it up and take it to your nearest waste disposal site
  • Alternatively, let the plant dry out and burn it in a bonfire or incinerator (woody plants with little soil on the roots burn best). However, burning creates pollution and may also annoy neighbours. Fires should be conducted when wind and weather mean that smoke will not enter houses or inhibit others from enjoying their garden. Here are some government guidelines on bonfires in smoke control areas

If you know the plant had a soil borne disease such as Phytophthora root rot or Verticillium wilt, consider removing soil from the root run and replacing with new topsoil or soil from an unaffected part of the garden. Take the affected soil to the tip or make use of it in the vegetable garden where there are unlikely to be susceptible plants. Soil replacement is only feasible with relatively small plants.

Plants that have died in their pots are less likely to have succumbed to a root disease so could be consigned to the compost heap. However, if there was any sign of a disease or vine weevil, take to the tip instead.

See our page for more advice on disposing of diseased material.

Replanting

Plants that have died of physical causes such as waterlogging, poor establishment or underwatering can be replaced with the same type of plant. Remedy any site problems such as poor drainage prior to replanting.

Plants that have been killed by a disease, in particular a soil borne disease (e.g. honey fungus, Phytophthora root rot or Verticillium wilt) or difficult to control foliage/stem disease (e.g. box blight) are best replaced with something that shows resistance. Lists of resistant plants or those not affected can be found on our advice pages of common garden plant diseases. Plants that suffer from replant disease (e.g. roses) should not be replaced with the same type of plant.

Leaving soil fallow (i.e. unplanted) for a given length of time does not guarantee success. However, grassing for a few years is a sound method if possible.

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  • City garden

    By City garden on 19/03/2016

    I have a well established vibernam in my green. The fit year of buying our house the large shrub/tree looked healthy and flowered. However last year the leaves started to brown and continued to deteriorate. The branches are now bare although lower on plant leaves appear green. I am considering digging it up as overall it does not look healthy. I would value advice. Thank you