You Ask, LAist Answers: Are Our Native Trees Better Suited For Climate Change Than Imports?

Earlier this week we published a story about how scientists are trying to find trees that’ll survive L.A.’s hotter and drier future driven by climate change, and we saw quite a bit of engagement.

Turns out a lot of you are interested in trees and have follow up questions! Which is quite exciting to me.

So I reached out to two arborists for help: Bryan Vejar with Tree People and Leon Boroditsky with the city of Los Angeles.

If you have any questions or tips, feel free to send me a note at the link at the end of the article. For those of you interested in planting trees that should do well in our changing climate, we also put together a planting guide.

Best trees for climate change?

It depends on the native tree. There’s a big difference between a heat-loving oak that thrives on a dry hillside and a sycamore which loves wet and cool riparian areas.

This western sycamore is growing along a stream in Porter Ranch, one of the hotter parts of the San Fernando Valley.

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Jacob Margolis

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The thick bark of a giant sequoia high in the Sierra Nevada has partially peeled away, revealing its insides.

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Jacob Margolis

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LAist

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Native plants in our area are adapted to a wildly variable climate with big swings between wet years and dry years, which has long been the norm in California. The problem is those swings are growing more extreme, and hotter temperatures put greater water demand on plants, meaning they need more than they typically would just to survive.

Drought-tolerant native oaks have struggled through our recent drought. And giant sequoias, which have grown in the same place for thousands of years, may not be able to get reestablished following recent fires because the climate in the area is now less than ideal. Climatic zones where certain trees thrive is changing.

I actually spent an entire episode of The Big Burn podcast talking about this.

Listen • 30:06

Transcript

Listen • 30:06

The Big Burn: Saving Our Giant Sequoias

Why trees that are adapted to living with fire are now burning… and how we might save them.

Transcript

That said, I’d prioritize lower water native trees when possible, though there are alternatives.

When asked, Boroditsky said he loves the native Torrey pine, which is beautiful, adaptable and quite drought-tolerant. If you’d like to see one in person, head to Reseda Park where there are some that are 80-feet tall.

A Torrey pine at Torrey Pines State Natural Reserve in La Jolla.

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Richard O. Barry

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Flickr

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Another thing to keep in mind: If you have a native tree planted on your property and it’s long survived off of lawn water and nutrients, making major changes to your landscape could put it at risk. It’s probably going to struggle if you pull that lawn out in favor of water-wise landscaping, because it’s adapted to having thirsty grass nearby.

The best parkway tree?

Ulmus parvifolia (Chinese elm) trunk and bark

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Chinese elms can be absolutely beautiful. Their wide, weeping canopies and stunning orange and gray mottled bark, can look great along any street.

That said, they may not be the ideal trees for every location.

They require a decent amount of maintenance — including structural pruning — throughout their lives. Some varieties are also susceptible to anthracnose, a disease which causes them to defoliate and leads to the formation of cankers that can girdle branches, make them structurally unsound and even kill the tree — though the ‘Drake’ variety is reportedly resistant.

They also require a low to moderate amount of water (more than the drought-tolerant species we highlighted) and their roots can be invasive. As they mature, if the parkway they’re planted in is too small, they can lift the pavement and cause structural damage. If they’re near a house, their roots can end up in pipes, as seems to have happened at our home, causing extensive damage.

“There’s no such thing as a perfect tree, and certainly Chinese elm isn’t a perfect tree. That said, it really depends on the parkway,” said Vejar.

If the parkway is large enough and if there are no utilities or pipes nearby, the Chinese elm can be a great option. That said, the water issue is a reasonable concern.

When asked for alternatives to the Chinese elm, Vejar suggested an African fern pine, which he called the “darling of the urban forest industry,” because it has low root damage potential and is extremely drought-tolerant.

Boroditsky, who’s partial to oak trees, recommended the native angelman oak, which he said is gorgeous once established. It doesn’t require as much maintenance as a Chinese elm and needs much less water.