Creeping Juniper - Ask Extension
I am working on a commercial site planting native plants. This site has a lovely Creeping Juniper defining it's curb driveway entrance. it's been the...
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Creeping Juniper #789445
Asked May 05, 2022, 2:18 PM EDT
I am working on a commercial site planting native plants. This site has a lovely Creeping Juniper defining it's curb driveway entrance. it's been there for many, many years and winters. At the beginning of this last winter it looked fine. This spring it is half dead. Please see the attached photos.
Can you please help me ID the damage cause? Can you please help me salvage this lovely plant?
Thank you.
Corliss
Howard County Maryland
Expert Response
Hello Corliss,
It's difficult to determine the exact cause of the dieback, as junipers are vulnerable to a few ailments. Plus, overlapping or consecutive stressors may have brought the plant to its tipping-point which led to overt symptoms of what may have been a chronic condition. Sometimes evergreens take surprisingly long to manifest stress. In either case, the brown branches will not recover and will need to be pruned off. If this leaves too little viable plant left, you might consider replacing them instead. While this type of juniper is native to North America (if it's a variety of Juniperus horizontalis, which it appears to be), it does not grow wild in the mid-Atlantic. Otherwise, if the plant's roots are healthy and the stressful conditions have passed, it should regrow new branches over time.
The ground-hugging forms of juniper sometimes provide an attractive shelter to voles, which can gnaw on bark for nourishment (or to wear-down their teeth). See if the bark at the base of any of the browned stems looks chewed or missing.
Several fungal diseases can afflict juniper. Different blight pathogens cause dieback, usually from the tips inward. Conditions keeping the foliage wet for long periods can encourage infection, such as drainage issues or frequent irrigation. You can try to inspect dead foliage for visible spores, though occasionally these might be due to secondary fungi that did not cause the initial damage. Management of blight diseases revolves around prompt removal of dieback as fungicides will not be reliable (or even effective in some cases). If irrigation was a contributing factor, make sure the system is only run manually when needed, or at least increase the interval between uses and run it early enough in the day so foliage is dry by nightfall.
Did this area receive piles of snow from road clearing this winter? Is ice-melting salt used on the pavement which may have been splashed (via road spray) or collected (via snow piles) onto the plants or soil in this area? You could investigate if there are nutrient excesses in the soil using lab testing; ice-melting products likely won't use sodium, but other "salts" used include minerals that should manifest on a soil test. Adding organic matter when replanting (or as a top-dressing if the plants remain) might help to bind-up or dilute some of these excesses, and some might be leachable using irrigation if the plants are dry enough to not get overwatered using this method.
Speaking of overwatering, junipers tend to be fairly intolerant of soggy soil. Was there any soil flooding in this part of the landscape, or a change in drainage patterns, such as adjustments in building roof drain outlets or a change in soil grade that redirected stormwater? Is there an automated irrigation system that runs regularly, and does it use a rain sensor? Root oxygen depravation from compacted, poorly-drained, or otherwise soggy soil can lead to branch dieback because the roots either die outright or become vulnerable to opportunistic infection by root-rotting fungi. If you do remove any of the junipers, you can inspect the roots for signs of infection. Usually, affected roots will be mushy, darker in color, and will be easy to pull apart with a tug. The inner stringy core will separate from the outer root sheath. In comparison, roots that are in good condition or which died from drought will take more effort to break and tend to cleanly snap in two.
As a less-likely scenario, did anyone treat this area with herbicide? (If they have done so before with no harm to the juniper, perhaps they changed active ingredients or used equipment that had residues of another herbicide.) Some herbicide ingredients can be absorbed by shrub roots, though this precaution will be mentioned in the label directions.
If you do replant and wish to use natives, we only have one species of juniper locally common in Maryland: Eastern Redcedar (Juniperus virginiana). We are not aware of any cultivars that are ground-hugging, but a few exist that are low-growing and wide-spreading shrubs. Common Juniper (Juniperus communis) has been documented in natural areas in northeastern MD, but is thought to be locally extinct there. However, you could use cultivars of this species as there are a couple which are ground-hugging. Otherwise, there are few evergreen native ground-hugging perennials, but if the site is sunny enough for the junipers, it should work well for Moss Phlox (Phlox subulata).
Miri
It's difficult to determine the exact cause of the dieback, as junipers are vulnerable to a few ailments. Plus, overlapping or consecutive stressors may have brought the plant to its tipping-point which led to overt symptoms of what may have been a chronic condition. Sometimes evergreens take surprisingly long to manifest stress. In either case, the brown branches will not recover and will need to be pruned off. If this leaves too little viable plant left, you might consider replacing them instead. While this type of juniper is native to North America (if it's a variety of Juniperus horizontalis, which it appears to be), it does not grow wild in the mid-Atlantic. Otherwise, if the plant's roots are healthy and the stressful conditions have passed, it should regrow new branches over time.
The ground-hugging forms of juniper sometimes provide an attractive shelter to voles, which can gnaw on bark for nourishment (or to wear-down their teeth). See if the bark at the base of any of the browned stems looks chewed or missing.
Several fungal diseases can afflict juniper. Different blight pathogens cause dieback, usually from the tips inward. Conditions keeping the foliage wet for long periods can encourage infection, such as drainage issues or frequent irrigation. You can try to inspect dead foliage for visible spores, though occasionally these might be due to secondary fungi that did not cause the initial damage. Management of blight diseases revolves around prompt removal of dieback as fungicides will not be reliable (or even effective in some cases). If irrigation was a contributing factor, make sure the system is only run manually when needed, or at least increase the interval between uses and run it early enough in the day so foliage is dry by nightfall.
Did this area receive piles of snow from road clearing this winter? Is ice-melting salt used on the pavement which may have been splashed (via road spray) or collected (via snow piles) onto the plants or soil in this area? You could investigate if there are nutrient excesses in the soil using lab testing; ice-melting products likely won't use sodium, but other "salts" used include minerals that should manifest on a soil test. Adding organic matter when replanting (or as a top-dressing if the plants remain) might help to bind-up or dilute some of these excesses, and some might be leachable using irrigation if the plants are dry enough to not get overwatered using this method.
Speaking of overwatering, junipers tend to be fairly intolerant of soggy soil. Was there any soil flooding in this part of the landscape, or a change in drainage patterns, such as adjustments in building roof drain outlets or a change in soil grade that redirected stormwater? Is there an automated irrigation system that runs regularly, and does it use a rain sensor? Root oxygen depravation from compacted, poorly-drained, or otherwise soggy soil can lead to branch dieback because the roots either die outright or become vulnerable to opportunistic infection by root-rotting fungi. If you do remove any of the junipers, you can inspect the roots for signs of infection. Usually, affected roots will be mushy, darker in color, and will be easy to pull apart with a tug. The inner stringy core will separate from the outer root sheath. In comparison, roots that are in good condition or which died from drought will take more effort to break and tend to cleanly snap in two.
As a less-likely scenario, did anyone treat this area with herbicide? (If they have done so before with no harm to the juniper, perhaps they changed active ingredients or used equipment that had residues of another herbicide.) Some herbicide ingredients can be absorbed by shrub roots, though this precaution will be mentioned in the label directions.
If you do replant and wish to use natives, we only have one species of juniper locally common in Maryland: Eastern Redcedar (Juniperus virginiana). We are not aware of any cultivars that are ground-hugging, but a few exist that are low-growing and wide-spreading shrubs. Common Juniper (Juniperus communis) has been documented in natural areas in northeastern MD, but is thought to be locally extinct there. However, you could use cultivars of this species as there are a couple which are ground-hugging. Otherwise, there are few evergreen native ground-hugging perennials, but if the site is sunny enough for the junipers, it should work well for Moss Phlox (Phlox subulata).
Miri
Many thank yous for your quick and in depth response. I'm most grateful a will check each suggestion with the exception of possible herbicide which was not used anywhere in this entire site.
I did have to water the newly planted natives a number of times but the Juniper while abutting the natives was not specifically included in the watering. Roots will be checked regardless.
With much appreciation.
Corliss
On 5/6/2022 1:12 PM, Ask Extension wrote:
You're welcome.
Miri, This is Part 2 of my Creeping Juniper concern. Unable to actually reach the roots I checked the main branching. It was firm, not at all soft. The soil was cool and damp, but we had just had two days of rain. I attempted to clip a few samples of the dead material and was surprised to find that these had separated from the main branchings and had simply lifted up with no attachment and no effort on my part, The ends, uniformly, looked as though they had been angle cut -an oblique neat, freshj cut. Some had a blue-greenish coloring at the detached end, almost all had a white mycelium-like growth on them. Photos are attached and hopefully they are reasonably clear enough for you to see this. The second photo has a small branch that is covered with this -or the damage of this-substance. Does this help with ID-ing what may be wrong, what may have contributed to this problem if we can ID it, what we can now do about it? Your response was very much appreciated. It was clear, covered the possibilities of problems and suggestions for salvaging. I am hoping that these photos will offer enough information to clarify the ID. If it is a fungus, can we tell which one, will it continue, will it pass on its own and not affect the new growth, is there anything I can do to suppress, minimize or prevent its return? Many thank yous, Miri. Corliss
Hello Corliss,
Thank you for the photos and updated info. Unfortunately, it's hard to tell what caused the initial damage. The branches themselves should never be soft, even when dead; it's only the roots where a noticeably mushier texture is one indication of root rot. Fungal growth on already-dead wood can be common as decay fungi colonize the new resource (since they consume dead wood and don't infect plants), so the presence of what looks like mycelium here may not be the cause of dieback. Usually, fungi that kill juniper stems produce spores within the dead needles, such as with both Kabatina and Phomopsis blight. We don't see the characteristic black spores in the sample pictured, but they might be hidden from view or on other stems.
The stem damage you describe is notable, since nothing should be causing the branch to detach from the main stem unless it was chewed away or physically broken. (Rarely do juniper branches root as they sprawl, but they always remain attached to the original center stem of the plant.) Dead wood tends to be more brittle than live wood, so may crack apart more easily when bent or tugged. If the breakage point was jagged as opposed to clean-cut, then we'd presume something physically crushed the stem when it was still alive -- a vehicle wheel, a person walking onto the planting bed, etc. Voles could be suspect for a cleaner cut, though they usually only gnaw-off the bark layer for nourishment and don't regularly cut stems completely off. That said, rodents do need to gnaw materials simply to wear-down their ever-growing teeth, so perhaps that would cause a vole to cut clean through a stem instead of only consuming bark. We think we see an example of stripped bark at the base of a stem in one of the photos, but that area is not in focus.
A fungicide is not warranted at this point, especially since we can't confirm a fungus was responsible. You may need to determine if voles are in the area. Our Reducing Vole Damage to Plants publication [PDF], while somewhat old, may be of use in determining what to look for and how to bait and/or trap to confirm the animal visiting that area is indeed a vole. There are several control options presented in that publication as well, though chemical methods should be the last resort after you confirm voles are causing the damage.
As far as preventing ongoing damage, for now, it's a wait-and-see approach if the pest responsible isn't a vole. A root ailment will likely continue to cause a progression of dieback on the remaining green growth, though there isn't much you can do about preventing it chemically (which is why waiting for additional symptoms isn't too risky). Although some soil-drench type of fungicides can help to suppress an infection (not all of which can be applied by the general public), it won't reverse existing damage, and a severely compromised root system may still cause the rest of the plant to decline further.
Miri
Thank you for the photos and updated info. Unfortunately, it's hard to tell what caused the initial damage. The branches themselves should never be soft, even when dead; it's only the roots where a noticeably mushier texture is one indication of root rot. Fungal growth on already-dead wood can be common as decay fungi colonize the new resource (since they consume dead wood and don't infect plants), so the presence of what looks like mycelium here may not be the cause of dieback. Usually, fungi that kill juniper stems produce spores within the dead needles, such as with both Kabatina and Phomopsis blight. We don't see the characteristic black spores in the sample pictured, but they might be hidden from view or on other stems.
The stem damage you describe is notable, since nothing should be causing the branch to detach from the main stem unless it was chewed away or physically broken. (Rarely do juniper branches root as they sprawl, but they always remain attached to the original center stem of the plant.) Dead wood tends to be more brittle than live wood, so may crack apart more easily when bent or tugged. If the breakage point was jagged as opposed to clean-cut, then we'd presume something physically crushed the stem when it was still alive -- a vehicle wheel, a person walking onto the planting bed, etc. Voles could be suspect for a cleaner cut, though they usually only gnaw-off the bark layer for nourishment and don't regularly cut stems completely off. That said, rodents do need to gnaw materials simply to wear-down their ever-growing teeth, so perhaps that would cause a vole to cut clean through a stem instead of only consuming bark. We think we see an example of stripped bark at the base of a stem in one of the photos, but that area is not in focus.
A fungicide is not warranted at this point, especially since we can't confirm a fungus was responsible. You may need to determine if voles are in the area. Our Reducing Vole Damage to Plants publication [PDF], while somewhat old, may be of use in determining what to look for and how to bait and/or trap to confirm the animal visiting that area is indeed a vole. There are several control options presented in that publication as well, though chemical methods should be the last resort after you confirm voles are causing the damage.
As far as preventing ongoing damage, for now, it's a wait-and-see approach if the pest responsible isn't a vole. A root ailment will likely continue to cause a progression of dieback on the remaining green growth, though there isn't much you can do about preventing it chemically (which is why waiting for additional symptoms isn't too risky). Although some soil-drench type of fungicides can help to suppress an infection (not all of which can be applied by the general public), it won't reverse existing damage, and a severely compromised root system may still cause the rest of the plant to decline further.
Miri
