Knowledgebase
Problem with mountain hemlock trees #751181
Asked May 20, 2021, 8:05 PM EDT
Hello,
I planted these mountain hemlock about three months ago and they have developed these problems of yellow leaves and falling needles. This didn't happen until recently. Three other trees planted in the same location at the same time are looking healthy and without this problem. Am I watering them too much? I have only watered them once every 7-10 days. They are planted in the same good soil as the other healthy plants.
I hope you can help.
Thank you.
Bob
Multnomah County Oregon
Expert Response
To troubleshoot possible issues with your mountain hemlock, Tsuga mertensiana explain how you planted them. Were they container plants? Did you remove all bindings and burlap (sometimes buried inside of mulch when a tree is bought in a pot). Did you amend the planting hole or re-install the native soil? Did you plant them the correct depth (looking for the root flare at the base of the trunk)? How did the root structure appear (were they root-bound, did you spread out the roots, corrective prune for any circling roots?) Any photos of the planting process?
The watering isn't something that can be scheduled for a new plant but needs to be done when needed. Check the root ball with your fingers. When the soil between the root ball and the surrounding garden soil is different textures, water has a hard time moving from one area to the other. This can mean that water might soak the garden soil and never get into the rootball, or the other way around.
Mountain hemlock is prone to some problems when grown in the valley because it is naturally adapted to higher elevations. I've heard reasonable drainage in winter helps, but can't find that in an Extension Service publication.
Here's the Oregon State Landscape Plants page for this tree. It will get too wide to be planted so near your paving.
"Selecting, planting, and caring for a new tree", EC1438 gives information about planting.
If you'd like to discuss your planting directly with someone via phone or email, contact the Metro Master Gardeners, here.
Thank you for your response. These were held in containers before planting. I'm not sure how long that was in the nursery. The bindings and burlap were removed before planting. The soil where they were planted is rich in organic material and new soil was mixed with that. The same as for the other trees that had the same pre-planting condition and are in the same soil and doing doing well without any yellowing. These two yellowing trees have space separate from the paving to expand roots without being affected by the paving.
I didn't do any corrective pruning of roots at time of planting.
Do you have any suggestions for actions for me at this time?
Thank you very much for your help. This service is very informative.
Bob
With no obvious planting errors, I will ask other experts to offer suggestions about next steps for you.
If you followed all of the best practices for planting as stated above, the best you can do is provide deep watering weekly. Try a liquid fertilizer every 14 days, like fish fertilizer or compost tea. Be sure to apply a nice mulch cover. Be patient as your tree adapts to its new location. Hope this helps!
Thank you for your help.
bob
