Urban sidewalk trees - what to plant?

In My Humble Opinion
1

Friends of the Urban Forest has a lot of suggestions of trees that don’t grow too big and so on, but I can’t sort through them very well to find what I want. I sent them an email for further help, but they never responded.

For an urban sidewalk tree, it needs to meet a number of criteria to get permit approval, such as not getting too large, roots that behave well, etc. Those are all a given for any tree selection.

Here is what else I am looking for:

Single trunk up to 7’ or so (once established) and then some kind of canopy of branches, as opposed to multiple trunks or branches that start low down.

Fairly drought-tolerant once established (this is San Francisco, and the climate is fairly dry). Yes, I will water as needed, but I would prefer a tree that doesn’t rely on that too much.

Fast growing is a plus, as I am not a fan of spindly trees that take 20 years to be able to stand on their own.

Fragrant (seasonal or whatever) flowers are a plus (not a flowering cherry, I am so over those).

Low maintenance: infrequent pruning or none at all, and please no dropping of annoying fruit or whatever that goes splat on the sidewalk and is difficult to clean. Also no bottle-brush trees.

Deciduous for preference, I don’t mind raking leaves, as long as I don’t have to scrape off splat.

It would be nice if it were a tree that attracted songbirds, if there is such a thing.

Simple, right? So what’s my perfect urban sidewalk tree?
Roddy

2

Outside our house we have Sorbus X Thuringiaca (a.k.a. Bastard Service Tree and Oakleaf Mountain Ash).

It’s pollution and drought resistant and makes a great urban street tree especially as (we have been reliably informed by a tree surgeon) its roots do not spread too widely, so there’s less risk of them causing heave/subsidence etc.

Be warned though, birds seem to love them so don’t park your car directly below one for too long!

ETA: If you follow the link above you’ll be able to click on some thumbnail images in the top banner and see its berries, autumn colour etc etc.

3

Flowering Pear. It thrives on high carbon monoxide levels, forms a decent amount of shade, and doesn’t drop random stinky garbage, like a Ginko (the worst of all street trees).

Eve though “flowering pear” is the correct answer, you can also consider Sycamore Maples, which are a popular street tree in NYC. They also like carbon monoxide, and don’t have a water-seeking taproot like many maples. They can get huge though, which may be a consideration for your sidewalk. They will shift it eventually.

Pin oaks can do well on the street, but grow slowly.

4

locust varieties generally get good ratings for urban settings - tolerant of salt/pollution, confined root space. iSTR ‘skyline’ being a recommended variety. I find they have very pleasing branch structures. The leaves turn a bright yellow in the fall, and are so small as to require no raking.

I know zippo about SF climes, tho.

5

You want to know what’s a BAAAAAAAD street tree? (Specifically, in terms of dropping predictable-not-so-random stinky garbage?) MANGO.

In Hawaii, there are mango trees all over the place. Every year in mango season, the sidewalks are covered with splattered mango carcasses, which get mushier by the hour, and rot, and get ground into the sidewalk as people walk all over them. Sheesh. What a mess. I’ll see your Ginko and raise you a mango. Yuck.

ETA: tl;dr for Roderick Femm: Don’t put in a mango tree. (Probably wouldn’t do well in S. F. climes anyway.)

6

We have a Linden, which has a nice shape and would make a good street tree. They don’t flower that you’d notice (very tiny), but they make seeds or something (OK, bracts, I’m told) with a lighter shade of green than the leaves.

We also have a pair of Liberty Elms, which are supposed to be resistant to Dutch Elm disease. Elms were very popular street trees, before the blight.

ETA: I’m in Michigan, and have no idea if these are options in SF.

7

Flowering plum trees are very colorful and don’t need much water. They are very popular sidewalk trees Arizona, I’m not sure how they would do with your cooler and wetter climate. When they bloom, they are truly beautiful.

8

There are a lot of Ginkgo trees where I am in Manhattan. They’re pretty cool-looking except the fruit make a mess on the sidewalk and they smell like puke in the fall. Otherwise a fine addition to any urban landscape :smiley:

9

Flowering plums, especially purple-leaf plums, and very common in the Bay Area.

You should know that San Francisco’s climate is very different from that of much of the rest of the country. Summers are cool, there is a lot of fog, winters are warm, it doesn’t rain half the year, droughts are common. . . A tree that works well in, say, New York, might do poorly in San Francisco.

Here is a list of trees recommended by the San Francisco Department of Public Works. I’d also suggest finding a copy of the Sunset Western Garden Book - it will tell you what microclimate you live in, and has detailed descriptions of many types of trees (and other plants).

10

On behalf of all of those of us who are taller, or walk in the wet, please make that 10’. Think about a tall guy with an umbrella. Also remember that branches bend down under the weight of the leaves.

11

I appreciate that, and city ordinance says 8’, but I was talking about while the tree is still younger (say under 10 years old). I would hope that the trunk would grow upwards over time and thus make this canopy higher.

Some good suggestions here. Thanks,
Roddy

12

As a Londoner, can I put a shameless plug in here for the London Plane which is mentioned in one of the PDFs in Jeff Lichtman’s link above.

They are a common and much-loved addition to the hot and grimy streets here, and they have absolutely lovely bark.

13

Sequoia sempervirens

14

Why not Adansonia digitata or Adansonia grandidieri? (Baobab)
Carweful with Ash, Emerald Ash Borer is spreading

Brian

15

Here we have dogwoods (not too tall but they tend to spread outward) but also scarlet oaks, London planetrees, Norway maples, lindens, and a few locusts. There’s also a few horse chestnuts and sycamores at the other end of the street, but that’s the older end of the neighborhood.

I have a dead mountain ash tree in front of my house. Thank you, emerald ash borers.

16

I figured the Sequoia was better suited to the coastal California environment, but those are good choices too.

17

A redwood tree would be too big for this purpose. It would destroy the sidewalk, and would grow tall enough to affect the neighbors’ view. I don’t think I’ve ever seen a redwood used as a sidewalk tree.

18

You’re right. Once you plant a tree there’s no way to get rid of it if it grows too large.

Also I wasn’t being serious when I first posted that, it’s probably not a great side walk tree, but then again, why not do it anyway?

19

Is this the same thing as a Bradford pear? If so, they’re planted a LOT around here but are highly un-recommended (or whatever … ) by arborists. Their wood is prone to splitting during storms, and they’re fairly short-lived.

They naturally grow in a very uniform shape that some people like but I think looks like a lollipop or a poodle’s tail. They coat themselves in white flowers every spring just before leafing out, which some people think are pretty, but the flowers smell like dirty socks if you’re clean-minded, or like sweaty crotch stank if you’re not.

The only good thing that I can say about Bradford pears is they have nice fall color - each leaf picks up multiple shades. That’s about it, though.

20

I know next to nothing about trees, this is just a personal observation.

In front of the house I rent is a buttonwood tree (I believe this is another name for a sycamore?). My neighborhood is an old one, with many very large trees. Many of the trees, including the aforementioned buttonwood, have roots that have apparently grown outwards, pushing up the sidewalks and distorting the lawns around them. I realize that it took decades for these trees to grow to the point that they are mangling the pavement, but you might want to think about which way the roots grow (straight down vs. sideways) on the tree you choose, if sidewalks are nearby.