|Background: Batch #1, Fall '99 planted 35, 5-6' shrubs, in shade - no problems, all still doing well. Batch #2, Spring '00 planted 40, same height, some in full sun, some in shade - no problems, all but one are doing well. Batch #3, Spring '00 planted 25 more, same height, shade - major problems, losing 100%. Nothing was different for 3rd batch, same rear yard, same planting mixture (50/50 top soil & licorice root mulch, supply of vermiculite and @ 5-10% composted cow manure). I do remember that the burlap balls were drier and more dense. Batch #3 planted in April/May.
After @ 6 weeks @ 4 of the shrubs showed signs of distress. I applied some MirAcid in water solution once per week. Then started to water more heavily. Shrubs worsened, brown throughout. After a week or two of heavier watering, more shrubs browned. This is when I noticed a single shrub from Batch #2 showed browning, but only on one side. This led me to think that I was watering too heavily, because where this shrub is affected is in line with some of the Batch #3 shrubs that were getting higher levels of water.
Questions: What can I do to save the shrubs if possible? What is the correct watering amount & schedule? Should I include Batch #3 in the Fall granular fertilization?
Thank you for your thoughts. They are most appreciated.
|Since the majority of the problem plants seem to be in one batch, I would begin by inspecting them carefully for signs of poor rooting and run some basic soil tests as this is possibly a soil problem (Different batches of amendments, different topsoils left after construction and so on could have different structure or properties.)
Failure to root can also be caused by a variety of things ranging from being poorly dug or handled during the sales/shipping process to being poorly planted or poorly cared for. (Obviously you have been doing a good job so far given that the other batches did alright.) However, uncooperative weather, pests and other problems can also come into play.
Unfortunately, arborvitae occasionally suffer from disease or infection, sometimes underground as a root based problem and sometimes systemic. They can also be affected by insects. Any of these could have the potential to spread. Based on your description, I am unable to tell long distance what has caused the plants to suffer.
Since there are so many of them and additional plants are showing signs of problems, I would suggest you consult with your county extension to try to determine the specific cause(s) and what to do next. It is important to do this quickly. You might also want to consult with the supplier of the shrubs you planted most recently to see if they have any thoughts on what has happened. I am sorry about your plantings!