Good Street Tree

Question from Kris:
The City is putting in a street tree in the 4ft parkway in front of my home.  They gave me a list of approved trees but my concern is potential root damage, drought tolerance, and excessive litter.  Which tree do you recommend: Acacia baileyana, Agonis flexuosa “after dark”, Malaleuca linariifolia, Geijera parvifloria, or Fraxinus oxycarpa “raywood”.  The acacia baileyana also has a purpurea variety. Thanks for your help with such a confusing choice.

Answer from Pat:
You mention that “the City” is putting in a street tree in the 4ft parkway in front of your home, but you do not tell me what City that is. I cannot advise you with any degree of certainly as to your choice of tree without knowing what city you live in or what climate zone and state. Judging by this list of trees, I am guessing you live in some interior zone of Southern California, but I am not sure. You might live in Florida. However, I am just going to guess you live in Southern California and not right along the coast. I agree with you also that this is a rather unusual list of trees to choose from. It is not a particularly well-chosen list, since though four of the selections are drought-resistant evergreen trees of roughly similar size, one is deciduous. Also the foliage and seasonal color of these trees widely differs in appearance so if every home owner on a particular block chose a different tree from this group they would be far from uniform if planted together.

Of all these trees, the one I personally like best is purple-leaved Bailey acacia (Acacia baileyana ‘Purpurea’). Therefore, if I were given this list this is the one I would choose, simply because I like it. However, it is interesting to note that there is a book called ‘Street Trees Recommended for Southern California” and Acacia baileyana is not included in it.  On the plus side A. baileyana is an evergreen, pest-resistant, and very drought-resistant tree once established. It is basically trouble free and easy to grow. Also the purple-leaved variety (A. baileyana ‘Purpurea’) is a somewhat rare and difficult tree to find (though perhaps growers are growing more of these now because drought is making them more popular.) Given a larger space for roots to grow, it would be an excellent choice.  Because of the leaf color and the February flowers which are extremely fragrant when in bloom, it is high on my list of desireable trees. The flowers are a brighter yellow than any other winter-blooming tree and the purple foliage is lovely also. Perhaps the one drawback is that this tree is considered short-lived but my experience is that with a little pruning every year after bloom to clean out dead wood and trim into a nice umbrella shape, it can last for many more years than the usual life span of 30 years. Cutting back lightly encourages new foliage and this improves the shape and health of the tree. Also, street trees are often changed with some frequency, so I don’t find the short-life factor to be a detriment. It is a fairly small tree so that is a benefit. There is one other problem with this tree and that is that if the tree is grown in clay soil it may have surface roots that lift sidewalks. This is why it’s not on the recommended list of street trees. However it will grow in just about any soil and if in well-drained soil the roots usually won’t be such a problem. If I were you I would plant it anyway and let the city deal with the consequences. They are the guys who chose this tree.

If you want to choose the most trouble-free selection among these trees, my choice would be the black peppermint tree (Agonis flexuosa ‘After Dark’). It’s an evergreen tree with weeping foliage that’s good for parkways, street-sides, medians, or growing in lawns. It can take either a little or a lot of irrigation, but needs irrigation at first to get started. However, about this tree I personally differ from many other horticulturists. I find the dark color of the foliage a bit gloomy unless you plant around it with enough green or other contrasting colors that show it up to good advantage. It’s good when light shines through it, but it’s pretty black when the sun shines directly on it. At least that’s what I’ve noticed so far. Why don’t you go to a nursery and look at one of them and then decide if you like it. You might also look for a photo on the Internet. Unlike the common green variety, we haven’t seen it growing long enough to find out all its characteristics. One thing is for sure, however, it’s smaller than the common green A. flexuosa. I have not yet seen a large one of these trees, but because it’s new and different, small ones crop up in every garden show at a County Fair or spring plant show that I’ve gone to in the last 5 or 6 years. Agonis flexuosa is an easy tree to grow in climate zones where the temperature never dips below 27 degrees Fahrenheit. Lower than that and it will freeze to the ground but may sprout again from the ground. It has no pest problems at this date and takes drought and salt winds. It is recommended as a street tree, but better in a 5 to 6 foot space, but then that is the recommendation for the larger one. The black one should fit fine in the 4-foot space and roots should cause no particular problems.

I personally chose to have two flaxleaf paperbark or snow-in-summer trees (Melaleuca linariifolia) planted in a median that is on the main street of our town at the foot of the street where I live. It is very drought resistant and takes wind, poor soil, heat, salt or sprinklers and once mature covers itself in summer with white bloom like snow, a breathtaking sight in bloom and a trouble-free tree in general. Unfortunately, the city where I live chose such small ones to begin with that the Founder of our garden club complained to me they are ugly. I begged her to please wait a few more years. I love this tree but if you don’t begin with a large enough specimen it takes forever to get going, especially if you crowd it with other plants as happened to the ones I had planted and they never watered or feed them to get them going. I think this is why we don’t see enough of these trees. Having told you I would have chosen the acacia, I now have to say I might choose this if they got me a nice large boxed specimen. I would love to see more of these trees on our streets. In Southern California this is highly recommended as a street tree. Cutouts 5 or 6 feet square are the best size but it could survive with 4 feet. Needs staking at first but be sure to take the stake off later so the trunk gets strong.

My advice is don’t choose Australian willow (Geijara parviflora) unless you are only interested in something trouble free. It’s adapted to heat and dryness but it’s a dull boring looking tree with weeping foliage, insignificant flowers, and it always looks a bit sparse on foliage. Why not choose something more fun? That said, it’s a good street tree, drought-resistant once established, and easy to grow. Will grow best in 5 to 6 feet but probably okay in 4-feet. No problems with roots and takes little or moderate irrigation and has no pest problems. Its only sin is that it can bore you to tears, poor thing.

All the above trees are evergreen but and none of them make a huge amount of litter, but now we come to Raywood ash or claret ash (Fraxinus angustifolia oxycarpa ‘Raywood’), a Mediterranean native tree, but this selection, noted for its handsome reddish-purple fall color (like red wine) is the only F. angustifolia oxycarpa selection grown in the west. Raywood ash is deciduous, that is it drops all its leaves in fall, but it doesn’t have any seeds. You mentioned you don’t want a lot of mess. If you plant this tree, you would have to rake up falling leaves every fall and early winter. Additionally, it’s prone to dieback in California which means dead twigs and limbs needing cutting out or raking up if they fall and it probably gets borers since all ash trees get them eventually. Ash trees usually have some kind of pest and disease problem, but people who want something that reminds them of a cold-winter climate yearn to plant ash trees anyway. This one needs moderate irrigation and I think needs more space than 4 foot wide, but probably would be okay. This is eventually a big tree and actually it grows pretty fast to 25 or 30 feet tall. This is the selection that does not seem in any kind of harmony with the rest of the trees on your city’s list, since it’s much bigger than the others, not as drought resistant as they are, and also is deciduous. Raywood ash is not a recommended street tree for Southern California, if that is where you live. The only ash that is recommended for streetside use in Southern California (in bigger spaces than your allotment) is Arizona ash (Fraxinus velutina) but I would not recommend this either since it is prone to a host of pest problems.