Doug Fir needles turning yellow or is it just me?

[Fir-man]

My Douglas Fir trees seem to be turning yellow-ish throughout the winter here in Washington State. What could this be from? I hardly ever water them in the winter cause it rains so much, and I bring them inside my garage whenever we have a cold stretch of 20F or colder for a few days. They were healthy and growing fine last summer. Any ideas? Or are they fine and I am panicking. This is southern washington state on the Oregon Border near Hood River, OR. Thanks!

 

[bdmatt]

What kind of soil are you using? With the decorative rocks, it's hard to tell. Overwatering may be an issue because of all the rain, roots being drowned and all.

 

[Fir-man]

I repotted most of these in the spring of 2022 with a 'succulent plant mixture' from a local nursery. Seems to drain well, but I also wonder if that has something to do with the slow yellowing these have been showing.

 

[Cruiser]

Are the needles drying/falling off or do they look healthy?
Winter temps and lack of sunlight can cause foliage to change color in some conifers up here. A clear-cut near me was replanted with Douglas-fir last Spring. Many of the saplings are a similar color as yours is but otherwise appear healthy.

 

[AJL]

You are using such a coarse free draining growing media its likely that nutrient deficiency will be part of the problem in a high rainfall area. Whats your feeding regime?

 

[Cruiser]

The needles and buds on these DF are ok despite the color. How do yours look?

 

[Eckhoffw]

You’re the Fir Man. Shouldn’t you know?

 

[Fir-man]

Are the needles drying/falling off or do they look healthy?
Winter temps and lack of sunlight can cause foliage to change color in some conifers up here. A clear-cut near me was replanted with Douglas-fir last Spring. Many of the saplings are a similar color as yours is but otherwise appear healthy.

Yeah thanks for the info. The trees seem pretty healthy to me. I'll keep a closer eye out to the clear cuts down my way and see if there are any similar looking doug firs

 

[Fir-man]

You’re the Fir Man. Shouldn’t you know?

Ha Ha. Yeah. Fir-man needs help

 

[Fir-man]

You are using such a coarse free draining growing media its likely that nutrient deficiency will be part of the problem in a high rainfall area. Whats your feeding regime?

Thanks for the feedback! I'm new to Bonsai, I have been using 4-10-3 FERTILIZER. 4% nitrogen, 10% phosphate, and 3% potash. Its a liquid fertilizer, diluted as prescribed on the container. I have used it once in mid summer 2022, and again in October 2022. What would you recommend? I cant say as though I have a regime figured out yet.

 

[yashu]

Is this a specific cultivar or a collected tree? I have a Lodgepole Pine that goes very yellow but it’s a specific cultivar propagated for that feature. If your tree was purchased from a nursery it could be a characteristic of the specific plant you bought.

 

[palafr01]

@Fir-man Do you still have some of that succulent soil around for a close up pic? I think your soil isn't draining too well, and yellowing needles on conifers is a common symptom. Being in Washington state you guys get a lot of rainfall, meaning your trees probably aren't drying enough in between waterings. If you do still have the bag of succulent soil also check to see if there's peat moss is listed as a component. Peat moss if used in high quantities can cause drainage issues (it also loves to compact leaving little airspace for roots).

Do note that I do not live near your area but your symptoms look very similar to some that I have experienced in the past. In fact I have an EWP that I just got that has had some needles yellow from being in a peat and bark nursery mix.

Don't panic there are several things you can do:

1) Do what you can to keep the soil drier (move trees around to shelter them from the rain etc.)
2) Use wedges and such to angle the pots to improve drainage (i.e. tilt the pots the best you can)
3) Use a chopstick and make holes throughout the soil to aerate the soil
related to #3, you can add a coarse aggregate (lava, pumice, etc.) into the holes to keep them open

If you are careful you should be able to guide your trees safely into the spring when they be repotted into better draining soil mix. Best of luck!

 

[ShadyStump]

If I had to render a guess, they're suffering from sleep deprivation.
20F is nothing to a Douglas fir. 5F you might start to think about extra protection, and settle on being lazy in stead, and still not be wrong.
They need the cold to keep them dormant. Anything above freezing and they wonder if it's spring.

In coastal Washington's climate it's barely cold enough for them to get enough rest as it. 50F rainy days and mid-30s at night is barely cold enough for them to stay dormant. In the high country here they handle subzero temps for days on end like it's nothing.
Outside 100% of winter in a shady north facing corner where it never reaches above 40 or 45 and they might be ok in your climate.

 

[0soyoung]

Western Washington is a Douglas fir forest, from the tree-line in the Cascades, down to the sea. But, I do believe that those in the Cascades are recognized to be a different subspecies from the costal Douglas firs.

I have a number of Douglas firs that I bought as 0-3 seedlings from Arborday (hence, their provenance is unknown). The foliage of a few of them is always yellow-ish and strongly more so during winter. I suspect these yellowish specimens may be a sub-alpine/sub-arctic variety.

Yellowing is a common mechanism of photocenter protection for sub-alpine/sub-arctic conifers in winter. The yellow color comes from an abundance of Xanthophyll that diverts photons away from the reactive center of PSII, The effect is to slow the rate of hydrolysis to match the decreased rate of enzymatic reactions in cold temperatures (hence preventing destructive 'sun burn'). There are some conifer species (such as junipers) that turn red instead, because they utilize anthocyanin to accomplish the same end by shading the photocenters. There are, of course, some 'mutants' that are very yellow/red even during summer (and now you know why these 'mutants' typically are weaker growers and are usually are greener in shade).

 

[yashu]

Western Washington is a Douglas fir forest, from the tree-line in the Cascades, down to the sea. But, I do believe that those in the Cascades are recognized to be a different subspecies from the costal Douglas firs.

I have a number of Douglas firs that I bought as 0-3 seedlings from Arborday (hence, their provenance is unknown). The foliage of a few of them is always yellow-ish and strongly more so during winter. I suspect these yellowish specimens may be a sub-alpine/sub-arctic variety.

Yellowing is a common mechanism of photocenter protection for sub-alpine/sub-arctic conifers in winter. The yellow color comes from an abundance of Xanthophyll that diverts photons away from the reactive center of PSII, The effect is to slow the rate of hydrolysis to match the decreased rate of enzymatic reactions in cold temperatures (hence preventing destructive 'sun burn'). There are some conifer species (such as junipers) that turn red instead, because they utilize anthocyanin to accomplish the same end by shading the photocenters. There are, of course, some 'mutants' that are very yellow/red even during summer (and now you know why these 'mutants' typically are weaker growers and are usually are greener in shade).

Thanks for that last paragraph. That’s all new information to me and super cool. I always wondered if there was some evolutionary advantage to that shift in color that some conifers have. I see it in some of the stands of pitch pine that I have near me.

 

[Alcam]

Took these photos today. I, too, would love to know for sure what's causing the yellowing, as I've questioned it for a few years now. I have permission to collect, so I think I'll do that soon and see if anything changes to them over time.