Newly planted Mugo Pines already checking out - Ask Extension
Planted 9 of them early June 2020, thrived through summer, felt like we watered consistently through winter. Planted in a large, long planter (25'x4'...
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Newly planted Mugo Pines already checking out #744305
Asked April 14, 2021, 1:10 PM EDT
Planted 9 of them early June 2020, thrived through summer, felt like we watered consistently through winter. Planted in a large, long planter (25'x4'x18" high) using a Planter's mix (sand/compost/soil?) with a gravel base. Browning started a month ago. All 9 reacting almost identically. Drought stress seems least likely to me, I suspect root rot or freeze damage, given they sit above natural grade. QUESTION: How can I tell what happened, and what should I do differently as a result? Really would like to make mugos work here, they seem easy for everyone else!
Jefferson County Colorado
Expert Response
Hello Eric,
Based on what I see in the photos, this appears consistent with freeze damage / winter dessication. It could also be a result of transplant shock. With the September 2020 sudden freeze they may not have been hardened off for winter, leaving needles susceptible to freeze damage. Here are some questions to help sleuth this out:
- Are the buds alive? Pinch them to see if they are pliable (live) or brittle (dead). Cut one in halve: if the inside is green, it is alive. Live buds should candle out later this spring. Over several seasons, the browned needles will drop off natually (part of the aging process) and the newer needles and branches will fill in any gaps.
- How did you water last season after planting? (frequency, amount)?
- Did you water over the winter?
- How deep is the planting mix layer? And how deep is the gravel layer? And what is beneath the gravel? Am asking these questions to evaluate possible soil texture interface issues.
- Have you had the soil tested? Sandy soil does not have much water holding capacity - depending on the % of compost in the mix, the soil may drain too quickly, which can lead to drought stress.
I look forward to hearing from you. Best regards,
Mari
Mari,
Thank you so much for the thoughtful reply. I'm really very grateful for you sharing your expertise.
1) I think most of the buds are dead. There are a few here and there that are still green inside, but those seem like they are just clinging to life.
2) How did we water? Poorly, I think. I water-settled the Planter's mix before planting, and then we were watering 3-4 times per week in summer, but with the hose. I kept putting off getting them mulched, making the excuse that so many woody bits from the compost had migrated to the top. I tried to be careful not to blast the rootball with water, but I was not the only one watering. Also, with the lack of mulch, we did battle hydro-phobic soil at the surface. Must have ended up being 8-10 gallons per week per plant.
3) Over winter, we were pretty careful during the dry times, trying to give a good soak at least every two weeks. I feel like that went better than the summer watering.
4) I'd say the mix is 14" deep, barely the same depth as the plug coming out of the pot when planted. Gravel layer is better described as rock layer, it varies from 4" - 8" deep, as the native soil sub-grade slopes from one end to the other, then out of the planter.
NOTE: This is my biggest concern. I build golf courses, so I have a rudimentary understanding of soils and drainage. When building greens, the most popular method involves creating a perched water table to help retain moisture in the sand profile. I was worried with this planter that the soil mix would migrate through the coarse rock layer, so at the last minute I put in a landscape fabric between the two layers. I began having second thoughts that it would seal up, so when I planted the pines I removed the "circle" of fabric at the base of the hole.
5) I should get the soil tested, but it has a lot of organic in it and seems to really retain moisture well. I will also check to see how it drains, doing a test hole in an area where there is still that fabric. I should have done that before planting, too.
With your help, and looking back, I now suspect that while the soil profile may have been sufficiently moist deep down, not having mulched them caused harm both in summer, and perhaps that September freeze, to the shallow roots near the surface? Could it be that simple? If that's the case, shame on me for such a stupid, lazy mistake. The 1 hour to install $40 worth of mulch is gonna cost me $900 to replace the pines!
Thanks again for your help, I look forward to hearing what you think about all this.
Cheers,
Eric
Eric Iverson
Partner
Renaissance Golf Design, Inc.
P.O. Box 228, Traverse City, MI 49685
Partner
Renaissance Golf Design, Inc.
P.O. Box 228, Traverse City, MI 49685
Cell: 720.339.1373
Hi Eric,
It is so good to hear from someone who already knows about soils!
I have a few ideas:
- It's possible that water drained out into the rock layer more quickly than it would have drained into native soil, resulting in drought stress (even though the soil has high OM).
- What is on the 'back' side of the bed where the fencing is? If not a very good insulator, the narrow bed may not retained enough heat to keep the roots from freezing. This would be similar to what can happen to potted plants left outside for winter: even if they are cold hardy for the USDA zone, the freeze/thaw of the roots can kill them. See Overwintering Container Plants .
- Lack of mulch is unlikely to have been the sole cause of the problem.
If you want me to check one of the plants to make sure there is not something else going on, you may submit a sample to the Jeffco Plant Diagnostic Clinic, located at the Jeffco Fairgrouns (Tu-F, 8-5). An entire branch would be OK; an entire plant would be best (transplant to a pot, in case it is viable).
I wouldn't pull all the mughos yet. Wait until June to see which ones candle out and how much damage there really is.
Best regards,
Mari
Again, thank you so much for your insight, I really appreciate it.
I may well bring a plant over to the Clinic, that's not too far away and having a definitive answer would give me relief to know what I'm up against long term with this planter. Probably toward the end of the week. I'll bring a soil sample, too, just for an "eyeball test" to get your thoughts.
The back side of the planter is merely 2"x12" boards stacked, and the other three sides are a wood framed wall, waterproofed on the inside, with the stone veneer outside. This seems like a good possibility of being the cause, seems like it could freeze fairly easily.
Maybe it is drought stress, which I suppose is always the prime suspect in our climate. Maybe we were late during a key stretch and they got away from us. But, even though there was a hole directly below each plant, the landscape fabric throughout the rest of the planter seems like it would have prevented any accelerated drainage?
I can't tell you how valuable it will be to have a solid answer, at this point the mystery of it is driving me nuts!
Cheers,
Eric
Eric Iverson
Partner
Renaissance Golf Design, Inc.
P.O. Box 228, Traverse City, MI 49685
Partner
Renaissance Golf Design, Inc.
P.O. Box 228, Traverse City, MI 49685
Cell: 720.339.1373
Thanks, Eric. I agree that cold or drought stress or both are the culprits, but a once-over at the Clinic would help us rule out anything biotic.
Best,
Mari
