Attractive Ornamental Flowering Trees

As I mentioned yesterday, I attended a class a tree identification class at the Arboretum taught by LA County plant pathologist Dr. Jerrold Turney. During the course of the lecture Dr. Turney recommended a number of striking, flowering ornamental trees. I thought I’d list a few of those remarkable trees in case you’re considering planting one. While this list is Southern California-centric, many of these trees can be grown in other climates. All images are courtesy of Wikimedia.

800px-magnolia_stellata_in_the_jardin_de_plantes_de_paris_001Magnolia stellata (Star Magnolia)
Small trees go with small houses like gin goes with tonic water. Small trees are also easy to maintain and don’t break the bank when it comes time to call an arborist. This tree is from Japan and will grow all over North America and Europe.

754px-cornus_florida_02_by_line1Cornus florida (flowering dogwood)
One catch with this pretty tree is that it’s susceptible to anthracnose.

800px-ipe%cc%82_roxo_ype-tabebuia_impetiginosa_cemiterio_sa%cc%83o_paulo_brazilTabebuia impetiginosa (pink trumpet tree)
A tough and beautiful tree that’s great for urban locations.


Tabebuia chrysotricha
Of all the trees Dr. Turney showed, I think this one was my favorite. The yellow flowers really pop out against a blue sky.


Brachychiton acerifolius (Australian Flame Tree)
Speaking of popping out, red flowers are also really dramatic.

chionanthus_retusus_-_chinese_fringetree_-_3Chionanthus retusus
Another good urban tree.

To these suggestions I’d add one of my own that also produces a tasty fruit:

redbaronRed Baron Peach
Plant one of these as a bare root tree this spring and you’ll have an attractive small tree and peaches!

Thanks to Dr. Turney for a great lecture. If you’d like to attend the other three parts of his tree identification class you can sign up here.

Trees Susceptible to the Polyphagous Shot Hole Borer

A beetle introduced beetle, the Polyphagous shot hole borer (PSHB), is causing the loss of many trees in Southern California. Kelly has blogged about this bug before but it’s worth repeating. It’s on my mind since attending a lecture this weekend by LA County plant pathologist Dr. Jerrold Turney.

I’ve learned, as a gardener, that there are certain plants in every bio-region that simply aren’t worth planting due to pest pressures. When it comes to trees it can be frustrating, expensive and downright dangerous to have a tree attacked by an incurable infection or pest. PSHB attacks hundreds of different tree species but is hosted on a more limited number. The list of PSHB host trees is growing as scientists study the problem. When Kelly blogged about the problem in 2015 the list of known host trees was 37. The list is now at 44. Here’s that list, via UC Riverside’s Eskalen Lab:

1. Box elder (Acer negundo)*
2. Big leaf maple (Acer macrophyllum)*
3. Evergreen Maple (Acer paxii)
4. Trident maple (Acer buergerianum)
5. Japanese maple (Acer palmatum)
6. Castorbean (Ricinus communis)
7. California Sycamore (Platanus racemosa)*
8. Mexican sycamore (Platanus mexicana)
9. Red Willow (Salix laevigata)*
10. Avocado (Persea americana)
11. Mimosa (Albizia julibrissin)
12. English Oak (Quercus robur)
13. Coast live oak (Quercus agrifolia)*
14. London plane (Platanus x acerifolia)
15.Cottonwood (Populus fremontii)*
16. Black cottonwood (Populus trichocarpa)*
17. White Alder (Alnus rhombifolia)*
18.Titoki (Alectryon excelsus)
19. Engelmann Oak (Quercus engelmannii)*
20. Cork Oak (Quercus suber)
21. Valley oak (Quercus lobata)*
22. Coral tree (Erythrina corallodendon)
23. Blue palo verde (Parkinsonia floridum)*
24. Palo verde (Parkinsonia aculeata)*
25. Moreton Bay Chestnut (Castanospermum australe)
26. Brea (Cercidium sonorae)
27. Mesquite (Prosopis articulata)*
28. Weeping willow (Salix babylonica)
29. Chinese holly (Ilex cornuta)
30. Camelia (Camellia semiserrata)
31. Acacia (Acacia spp.)
32. Liquidambar (Liquidambar styraciflua)
33. Red Flowering Gum (Eucalyptus ficifolia)
34. Japanese wisteria (Wisteria floribunda)
35. Goodding’s black willow (Salix gooddingii)*
36. Tree of heaven (Ailanthus altissima)
37. Kurrajong (Brachychiton populneus)
38. Black mission fig (Ficus carica)
39. Japanese beech (Fagus crenata)
40. Dense logwood (Xylosma congestum)
41. Mule Fat (Baccharis salicifolia)*
42. Carrotwood (Cupaniopsis anacardioides)
43. California buckeye (Aesculus californica)*
44. Canyon Live oak (Quercus chrysolepis)*

If you have any of these trees here are UC Davis’ shot hole borer management suggestions:

Protect your trees and local habitat from a variety of pest species by avoiding moving infected wood around – use firewood locally.

PSHB has been found to attack healthy trees, but as always a good defense against disease is to keep trees in optimal health. Healthy trees are also more likely to recover more quickly from an attack. Choose trees that are appropriate for the site and don’t require a lot of additional water. Provide appropriate soils and access for roots to grow and expand. Avoid excessive pruning, over- or under-watering, and planting inappropriate companion plants within the dripline. If trees are infected, systemic insecticides generally are poor for treating ambrosia beetles. Prophylactic spraying of the bark could be used to protect uninfected trees in some situations. Sterilize pruning tools between uses to avoid spreading the fungus. This handout can guide you through deciding when to remove an infested tree, and how to handle the wood waste.

Chipping and solarizing/tarping infested wood can help to limit the spread of the beetle/fungus complex. Wood should be chipped to pieces smaller than 1″.

Misguided water conservation efforts have, in my opinion, contributed to the problem by stressing our landscape trees. You should keep your trees appropriately watered. And it appears that with many of these trees, including avocados, prophylactic spraying with a pyrethroid-based pesticide every three to four months will be necessary.

Dr. Turney is doing three more tree identification lectures at the LA Arboretum. More information here.

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Nassim Nicholas Taleb on GMOs and the Precautionary Principle


With the prospect of a Monsanto/Bayer mashup GMOs are back in the news.

In an interview from 2015, former trader and risk management expert Nassim Nicholas Taleb presents what I think are some of the best arguments against GMOs. In this podcast Taleb tackles:

  • The statistical errors found in scientific papers
  • The need to apply the precautionary principle
  • The unacknowledged risks of catastrophe
  • The technological salvation fallacy

In short, it’s not about the health risks of eating a GMO corn chip. It’s more about the way we discount and misunderstand risk. Consider Taleb’s argument the biological equivalent of what happens in The Big Short (a film in Netflix that’s well worth viewing).

You can listen to Taleb’s interview and download it here.