Regional Gardening Reports :: National Gardening Association

In the Garden:
Southwestern Deserts
December, 2010
Regional Report

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Olives ripen at different rates on the tree.

Olive Trees

During a recent visit to an older Phoenix neighborhood, I came across quite a few olive trees, still loaded with (or dropping) fruit in varying stages of ripeness. Native to the Mediterranean region, olive trees were brought to the Southwest by Spanish missionaries in the 1500s for their fruit and oil production. The trees were right at home in our hot, arid surroundings and rocky soils.

Modern-day homeowners and developers transplanted olive trees into landscapes for the evergreen canopy of silvery foliage that provided shady respite and interesting structural shapes formed by their trunks as they matured. The trees were also appreciated for their longevity.

Unfortunately, common European olive trees (Olea europaea) are copious pollen producers, creating havoc for allergy sufferers. (Rather ironic, since so many people move to or visit the Southwest to alleviate respiratory ailments.) Olive trees are covered with lightweight pollen that is easily windborne from spring to early summer (usually March or April to May or June, depending on locale). In Allergy Free Gardening (Ten-Speed Press, 2000), author Thomas Leo Ogren gives olive the highest number (10) on his 1 to 10 ratings scale of plants to avoid adding to landscapes because of their allergy potential.

Many areas where olives grow in the Southwest, such as Clark County (Las Vegas, NV), Maricopa County (Phoenix, AZ), and Pima County (Tucson, AZ), now ban the planting of common olive trees because of their pollen production. Extensive fruit drop is another drawback because it creates a mess that requires cleanup. However, most municipalities make an exception for a pollenless and fruitless variety, such as 'Swan Hill.' Save yourself time and money by checking with local plant restrictions in your area before planting.

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