What is wrong with these juniper and what do I do about it?
These Blue Pacific Juniper were put in on this hill (009.jpg)in front of our house in September 2001. It faces east and is in full sun most of the time, especially in summer. For several years, it did very well. In recent years, there have been what look like burrows into the plant (005.jpg) and several feet of denuded branches ending in new growth at the tip of the branch (oo6.jpg). A late frost in Spring 2014 produced a lot of die-back. I waited to see what if anything would come back. It now looks as you see in the photos. Do I cut back to the green growth near the main plant itself. Do I replace the plants? What do you recommend as a replacement? What do you think of Thuja koraiensiss as a replacement? What about Ilex crenata Golden Heller (Japanese Holly) or Cephalotaxus harrintonia prostrata (Japanese Plum-Yew?) Thanks in advance for your help.
Montgomery County Maryland
In our previous answer to you a few days ago, we enumerated the possibilities of what may be wrong here. (see below)
We notice that in your photo the worst browning parts appear to be in shade. If this area is not in full sun, juniper will continue to decline and you could spread out your pachysandra bed to fill in. If there is still good sun here, you could install similar junipers.
At this point, we'd suggest pruning out all the dead material and see what you have left. Prune back to green growth. Rake up the area and as you do note if you are seeing runways from voles, and consider doing some trapping to bring the numbers down.
The three plants you mention are woody, and almost shrub-like proportions, some 2-5 feet high. We don't have a lot of research or practical experience growing these particular plants. Michael Dirr's Manual of Woody Landscape plants is a common reference we use in this case( it can often be found in the reference section in a library). His remarks on Thuja koraiensis say "...is usually a broad, rather irregular 2-5' high spreading shrub of no great beauty" We doubt that's what you had in mind for this area.
Other options to consider can be found on a chart in our Groundcover publication at this link: https://extension.umd.edu/sites/default/files/_images/programs/hgic/Publications/HG89%20Ground%20Cov...
Previous answer: "The junipers do not look like they are happy in the above site. Junipers usually look good once planted and after a while decline due to lack of sunlight, winter injury, vole damage, http://extension.umd.edu/hgic/voles possible diseases, poor drainage, etc. Junipers grow best in full sunlight and a well drained soil. They will thin out and brown due to lack of sunlight. They also may have been affected by our cold winter. At this point, all you can do is prune dead plant material. You can also put new ones plants in to fill in or replace with another type of groundcover. Either way, it is a lot of work. If you replace, you should put in a variety of plants so you do not lose the entire stand to an insect or disease issue.
Thank you for your quick response. As a point of clarification, I did not receive your first reply. That is the reason for my reposting the question. As I mentioned in my second posting, that area gets full sun all year, all day. The photos were take in late afternoon-early evening. A friend suggested replacing the plants with vinca. Do you agree?
Vinca is a possibility for you. It is included on the groundcover listing sent with our last reply- take a look at it's description, which is the last one on the page. The biggest consideration with this one is that it can be invasive and shouldn't be installed in an area where it could get away from you into natural areas. It looks from your photo that the sidewalk would stop it and this wouldn't be a problem for you.