African sumac, not native to the Tucson area, is not a good alternative to palm trees. The Arizona Native Plant Society calls it an "invasive weed."


So much for working from home. Sitting in my backyard and writing last week, I was seduced by a pretty tree waving at me in the breeze. It was an African sumac, and I pointed to that species in last Wednesday's column - on the scourge of palm trees - as an example of a good non-native tree to plant.

"You hate palms but you like African sumac??? EEE Gad." That email comment from Tucsonan Kenneth Coppola pretty much summed up readers' reactions to the column. Almost all agreed that people have planted too many palms in Tucson, but said African sumac are about as bad, if for different reasons.

Reader Jane Spalding explained: "I have to object to your reference to African sumac (Rhus lancea) as an alternative non-native choice for planting here in Tucson. With research you'll notice it is considered an invasive species; our native birds don't eat it or use it for nesting materials, and the mat of sucker roots that spread out beneath it choke our other growth over time."

And she didn't mention their abundant allergy-producing pollen. Maybe that's what clouded my judgment.

Planting native vegetation seems increasingly popular - trees such as the velvet mesquite, blue palo verde and desert willow - because they thrive here without as much watering and care, and they are part of the indigenous ecosystem.

Still, there are a number of non-native trees that work well in the Tucson area - low-water use, non-invasive, not too allergenic - which is the point I was trying to make. The danger is that Tucson has a long history of adopting non-native trees, only to cast them out later as invasive or unwanted.

Consider this headline from the March 29, 1912, Arizona Daily Star: "EUCALYPTUS HAVE TRIAL IN ARIZONA." (They used all capital letters in the main headlines in those days.)

The story, with a Bisbee dateline, reads, "An experiment with eucalyptus trees will be conducted on the Warren ranch. A hundred of these hardwood trees are being planted on the ranch this week for the purpose of determining whether the tree is adapted to this part of the country and if the experiment should prove that they are it will be of inestimable benefit to the county."

A hundred years and thousands of eucalyptuses later, relatively few people are planting them in Southern Arizona anymore. That's largely because they grow too big for many properties, have big roots that crack pavement, and constantly shed bark and branches, said Roger Putney of Civano Nursery.

African sumac has taken a quicker path to obsolescence in the Tucson area. It came to Arizona from South Africa in the 1920s and was planted heavily during the 1970s. Now it's considered, in the words of the Arizona Native Plant Society, an "invasive weed."

Katie Gannon, who runs the Trees for Tucson program for Tucson Clean & Beautiful Inc., recently revised the group's recommended trees list, for the first time in 15 years. It was an arduous process of talking to arborists and others.

The result is about 10 recommended trees for each of four different categories: For schools or parks, as street trees, under powerlines and especially drought tolerant species.

"When it comes to plants, everyone is very opinionated and passionate," she said. "We have eras of plant palettes that we just keep adding to."

Gannon removed some Australian natives from the list because they aren't cold-tolerant enough to withstand the hard frosts we've had in recent winters.

Most of the recommended trees are native to the region - mesquites, palo verdes, ironwoods and the like. But there are several from outside North America. The Chinese pistache has been a favorite of late. So has the Afghan pine, which has displaced the once-popular Aleppo pine on many nurseries' lists.

But I'm getting worried about recommending non-native plants. The next one I suggest might turn out to be a loan shark.

Might be better to follow the advice of the reader Ken Coppola, who, it turns out, collects seeds and propagates plants as part of the University of Arizona's Desert Legume Program.

"It's probably better to stick with things that are native or things that have been here so long that they've adapted and live well because they're adapted to the desert environment."

Trees recommended for different Tucson situations

Katie Gannon of Trees for Tucson recently revised a 15-year-old list of recommended trees for planting in different situations in Tucson. The list eliminated some species native to Australia, because they've proved intolerant of the hard frosts common in recent years.

The nonprofit group Tucson Clean & Beautiful Inc. runs the Trees for Tucson program, which offers shade trees at low cost. Call 791-3109 for more information.

At schools or in parks (with turf and turf irrigation)

1. Olive/Olea europea X 'Wilson', 'Swan Hill' (non-allergenic varieties)

2. Arizona ash/Fraxinus velutina

3. Desert willow/Chilopsis linearis

4. Mesquites/Prosopis velutina, hybrids

5. Hackberry/Celtis reticulata

6. Pistache/Pistacia chinensis

7. Red oak/Quercus buckleyi

8. Aleppo pine/Pinus halepensis

9. Afghan pine/Pinus eldaricaf

10. Blue palo verde / Parkinsonia floridum

As street trees

1. Mesquites/Prosopis species and hybrids

2. Blue palo verde /Parkinsonia floridum

3. Palo brea/Parkinsonia praecox

4. Desert museum palo verde /Parkinsonia X

5. Ironwood/Olneya tesota

6. Desert Willow/Chilopsis lineris

7. Catclaw acacia/Acacia greggii

8. Texas ebony/Ebenopsis ebano

9. Kidneywood/Eysenhardtia orthocarpa

10. Feather bush/Lysiloma thornberi watsonii

Under power lines

1. Catclaw acacia/Acacia greggii

2. Whitethorn acacia /Acacia constricta

3. Texas mountain laurel/Sophora secundiflora

4. Feather bush/Lysiloma thornberi, watssonii

5. Kidneywood/Eysenhardtia orthocarpa

6. Texas ebony/Ebenopsis ebano

7. Screwbean mesquite/Prosopis pubescens

8. Kidneywood/Ebenopsis ebano (pithecellobium flexicaule)

9. Arizona rosewood/Vauquelinia californica

10. Cascalote/Caesalpinia cacalaco

Most drought tolerant

1. Velvet mesquite/ Prosopis spp and hybrids

2. Foothills palo verde / Parkinsonia microphylla

3. Blue palo verde/Parkinsonia floridum

4. Palo brea/Parkinsonia praecox

5. Desert museum palo verde / Parkinsonia X

6. Desert Willow/ chilopsis linearis

7. Ironwood/Olneya tesota

8. Catclaw acacia/Acacia greggii

9. Whitethorn Acacia/Acacia constricta

10. Kidneywood/Eysenhardtia orthocarpa

Contact columnist Tim Steller at or 807-8427