Coast Redwoods survive without Coastal Fog

Is seed germination the real key to Sequoia sempervirens' natural range survival?

by Mario Vaden

This page is about the survival of the coast redwood and the natural range. For a number of years I felt that too much emphasis may have been put on fog in relation to the species' survival. The key to survival may be related to germination of its seeds and the survival of saplings. This came to mind for several reasons including coast redwoods like the one shown below in Medford, Oregon

This coast redwood is one of the better looking landscape specimens I've seen aside from the codominant leader that parts half way up. Consider this .... Medford gets only 19 inches of rainfall per year !! Yes. just 19 inches. Less than 1/3 of what Crescent City gets and 1/4 what Jedediah Smith park receives. And this part of southern Oregon gets virtually no summer fog June to October. Yet this redwood is flourishing at 139 ft. tall and 6.4 ft. diameter dbh., and it's a young redwood. Continue reading below the image.

Due to a few people at Facebook trying to say this a cherry-picked example in conversations related to rain and irrigation. Let me add that most redwoods in the Medford area look okay, even without watering. The example below pertains to the context of whether fog is needed for a tree to survive or not. But if people want to know about rain and redwoods, even redwoods without irrigation in our area remain green if the soil is okay. That's most of the redwoods, aside from the ones in worst of the worst spots like between sidewalk and street in the tiny planting strips. There's 100 footers around here that get no irrigation and are green all the way to the apex. For example, go to Costco in the adjacent Central Point city and look at the big redwoods off Table Rock Rd. in view to the north. Those don't get irrigation, yet remain green and stand tall. Even with temps sometimes hitting 113 degrees F or more. The redwoods may not be growing at their optimum, but they can endure and remain an attractive green color. Anyhow, some people have posted online that redwoods can't live inland in an area like Medford without irrigation. And that's foolishness or ignorance with so many redwoods as living witnesses to the contrary. That doesn't mean you can't water them. I'm just noting what many of them can endure. It's not just opinion because the redwoods growing around here are factual.

 

 

I've worked in Washington, Oregon and northern California doing tree and landscape work since 1980. But I grew up around forest from 1963. During all these years, I watched which species would just grow at various properties, and which species germinate seeds and grow. For example, the vine maple Acer circinatum is a native plant to Oregon, Washington and California. Not only does it grow, but the seeds germinate in landscape and in forests. Likewise, Japanese maple seeds germinate too, sometimes by the hundreds, even though it's indigenous to Japan, and not to our west coast.

But in all my professional years of horticulture, I do not recall seeing coast redwood seedlings sprout in residential landscapes, golf courses or municipal parks in all of Oregon or Washington. Doesn't mean it never happened ... but I haven't seen it happen.

So realizing that coast redwoods grow very well throughout much of OR and WA without relying on fog for survival, I began to wonder if coastal northern California has something else worth pin-pointing pertaining to why the coast redwood forest is native to that area. Could it have been natural forest fires clearing the ground? Hard to tell anymore, because redwood forest fires are supressed by man.

Seeds have special needs, and the needs vary by species. If I recall correct from Seeds of the Woody Plants of the United States, the Mt. Ash seeds need about 30 straight days below freezing, twice. That doesn't happen in the lowland of the Willamette Valley, but it will occur half way up Mt. Hood. We can plant and grow Mt. Ash in most west coast cities, but the chance of finding a germinated seedling at low elevation with moderate climate is near zilch.

So with the coast redwood, I throw down the gauntlet for someone to narrow-down the exact requirements of the species survival. Not what it takes for them to get big, because certainly lots of fog and rain achieves that. But why do they reproduce in that area and don't readily reproduce elsewhere? The real key to survival is reproduction, not growing to gargantuan volume.

Back to this coast redwood in the photo. I've seen plenty this big through OR and WA. But this one better than most makes the point what coast redwoods can endure without fog. If you are not familiar with this part of the Rogue Valley, the rainfall is the 19 inches yearly that I mentioned. And summer temps of 85 to 100 degrees are common. About 6 to 8 degrees warmer than Portland, but half the rainfall. This redwood went through two of the driest growing seasons in 2014 to 2016. The winter of 2016 - 2017 saw temperatures down in the teens, Farenheit, and a 100 yr. snowfall event that hammered trees from this Jackson county all the way over to Del Norte county. Yet, the folilage of this Sequoia sempervirens is gorgeous. In 2018, it experienced 114 degrees, and remains green. In 2022 temps soared to 90's, 100's and briefly to 115 degrees F.

What I wrote above shows that redwoods can approach the size shown without fog or irrigation in a region like Jackson county where Medford, Oregon is situated. Provided the amount of soil and space isn't abnormally limited. But when these redwoods grow even bigger and taller, and if soil depth has certain limits, maybe irrigation will be required in the future. I don't know if a 200 foot coast redwood can grow in Medford without supplemental water. I do know that Sequoiadendron can exceed 200 feet without supplemental irrigation because we found a 212 foot world record for non-indigenous recently that's now 214 feet tall. Also in Jackson county, planted in a forest where there's no irrigation.

Coast redwood would not be one of my personal choices to plant here in southern Oregon. But if you do plant one, then make sure there's lots of soil around it in a big space.