about 5 of my blue rug junipers died this summer - Ask Extension
I used to have two rows of them going down the slope where my flagstone steps are on the south side of my house. They've done well for 20 years. It ...
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about 5 of my blue rug junipers died this summer #885489
Asked September 16, 2024, 5:27 PM EDT
I used to have two rows of them going down the slope where my flagstone steps are on the south side of my house. They've done well for 20 years. It gets full sun. But this summer half of one of the rows the plants turned brown and died. Don't know if my lawn guys maybe put a bit too much mulch around them, or whether it was the extreme heat we got. I've trimmed them only minimally over the years (should I trim more to salvage the remaining ones?). Should I replace them with the same thing? Do I need to adjust the soil? Do I need to fertilize them if I do that? And same for the surviving ones, to keep them from going brown and dying? Any suggestions would be most appreciated. I sent two photos to Kaitlyn Baligush but they would not attach here.
Montgomery County Maryland
Expert Response
We have asked Kaitlyn to send us the photos you shared with her, though if the attach-file function is not cooperating on your end, you could also paste images directly into the body of your reply instead. (Please make sure they're at least 1MB in size so we can enlarge them.) Until we receive them, we'll make a couple educated guesses as to a diagnosis.
Too heavy of a mulching can interfere with root health as well as harbor certain pests (in this case, mainly voles that might have chewed into the base of the main stem(s)). A mulch layer should be no more than 3 inches thick over a plant's root zone, and not piled against its main stems or base. Our primary suspect in this case, though, is moisture-related...were the junipers being monitored for watering needs during this year's drought (which is still present in parts of the state, including most of Montgomery County)? Even though junipers are known for their good tolerance to drought, it is just that -- a tolerance, not a preference -- and they can be pushed over their limits and succumb to damage if the roots get too dry. The drainage or moisture retention between the two planting sites, despite how close to each other they are, could still differ and result in different rates of drying out for each planting. Is either location in competition with any nearby tree roots, even if the shade from that tree isn't overshadowing the junipers?
Fertilizer does not benefit stressed plants, and may actually make the situation worse if a nutrient deficiency in the soil is not the sole reason for plant damage. (It would not be here, given the symptoms you describe.) Established shrubs, junipers included, should also not need routine fertilization.
Junipers should not need regular pruning, though they will tolerate a bit if it's needed to remove errant growth or restrain size a bit (drastic pruning to restrain size is not as well-tolerated and can lead to dieback in certain circumstances). For plants with brown branches, those stems will not recover and will need to be pruned off back to where they join still-living wood. Healthy growth should not need trimming, and any plant wound (even from sharp pruners) does run a risk of becoming infected or colonized by wood decay organisms, so each pruning cut on a shrub or tree should be made with good reason. For junipers with too much brown growth (dieback), or if any plants turned entirely brown, they will need to be removed/replaced instead since they cannot recover. You can replace them with the same variety if you prefer a symmetrical look, and if the site doesn't have conditions (like too much shade or poor drainage) that conflicts with the needs of the juniper. For example, if drought was the primary cause of their demise (our working theory so far), then replanting should be fine.
Miri
Too heavy of a mulching can interfere with root health as well as harbor certain pests (in this case, mainly voles that might have chewed into the base of the main stem(s)). A mulch layer should be no more than 3 inches thick over a plant's root zone, and not piled against its main stems or base. Our primary suspect in this case, though, is moisture-related...were the junipers being monitored for watering needs during this year's drought (which is still present in parts of the state, including most of Montgomery County)? Even though junipers are known for their good tolerance to drought, it is just that -- a tolerance, not a preference -- and they can be pushed over their limits and succumb to damage if the roots get too dry. The drainage or moisture retention between the two planting sites, despite how close to each other they are, could still differ and result in different rates of drying out for each planting. Is either location in competition with any nearby tree roots, even if the shade from that tree isn't overshadowing the junipers?
Fertilizer does not benefit stressed plants, and may actually make the situation worse if a nutrient deficiency in the soil is not the sole reason for plant damage. (It would not be here, given the symptoms you describe.) Established shrubs, junipers included, should also not need routine fertilization.
Junipers should not need regular pruning, though they will tolerate a bit if it's needed to remove errant growth or restrain size a bit (drastic pruning to restrain size is not as well-tolerated and can lead to dieback in certain circumstances). For plants with brown branches, those stems will not recover and will need to be pruned off back to where they join still-living wood. Healthy growth should not need trimming, and any plant wound (even from sharp pruners) does run a risk of becoming infected or colonized by wood decay organisms, so each pruning cut on a shrub or tree should be made with good reason. For junipers with too much brown growth (dieback), or if any plants turned entirely brown, they will need to be removed/replaced instead since they cannot recover. You can replace them with the same variety if you prefer a symmetrical look, and if the site doesn't have conditions (like too much shade or poor drainage) that conflicts with the needs of the juniper. For example, if drought was the primary cause of their demise (our working theory so far), then replanting should be fine.
Miri
Thanks very much, Miri. I did sent you another reply just now and pasted two pictures into the body of it. Let me know if they give you any further thoughts.
But I think your message sounds like the right answer. I'll buy about four or five more Blue Rugs and plant now since it is Fall. Then, next summer, I'll be more careful about watering. I might use a soaker hose that I have.
Cordially,
Dave
Thank you for the photos. It's hard to see enough detail in the close-up photo as it appears to be out of focus or lower in resolution, but for the other image, site conditions does appear to be the primary factor involved. (Heat reflecting/radiating off the wall and the wall also limiting airflow, plus the slope's drainage potentially drying out that area more quickly (though not all slopes drain very well).) The mulch doesn't appear to be laid too thickly, though it's hard to tell. Soaker hoses can be a great way to water while conserving moisture, but check on them once in a while to make sure they're still functioning normally along their entire length, since sometimes (in a drought especially), thirsty wildlife (rodents or rabbits, mostly) might find them and chew into them, making them leak.
Miri
Miri
Thanks again, Miri,
If the site conditions (the wall = side of house) would that indicate not replanting blue rugs there? Or can I go ahead and just water more diligently next summer?
Dave
More monitoring for watering needs should suffice if you replant, as Juniper should still be okay for those conditions (or succulents, like Sedum and other options). A mix of groundcover species would provide better resilience overall and less vulnerability to the same issues at the same time, potentially allowing the planting to not suffer damage as extensive as before in times of stress, but that won't look as uniform compared to the other side of the stairs, if a symmetrical aesthetic is important.
Miri
Miri
Excellent - Thanks!!!
You're welcome!
