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The Master Gardener Journal


A   B O U N T I F U L   G A R D E N


A Date with History
by Janice Austin, Master Gardener

The Phoenix area has been called an oasis in the desert, with its many resorts, swimming pools, and also, for its many exotic palm trees. Bold sunset silhouettes of palm trees harken back to an earlier time in Arizona history, when significant numbers of these lofty, swaying palms could be spotted in the landscape. Remnants of the past can be found in older Phoenix neighborhoods, still standing tall today.

Louisa Ballard, a Master Gardener for seven years, and program coordinator of the Arboretum at Arizona State University in Tempe, knows a lot about the Palmae family members cultivated in our area, and about date production, too. Along with horticulturalist, Richard Harris, who put in much of today's collection, Ballard maintains an extensive variety of palms at the Arboretum.

Ballard explains that historically palms were considered to be ideal trees for a "retirement" state like Arizona, requiring little work and providing little mess‹theoretically. Members of the Palmae family, such as Bahea armata, Mexican Blue Palm, and Washingtonia robusta, Mexican Fan Palm, and the shaggier, stockier and sometimes bearded Washingtonia filifera, Californian Fan Palm, lent stately elegance planted along the city's broad avenues in early Phoenix. Some of these sported the labor-intensive "shovel-cut" pruning, called "pineapple palms" for their distinctive shaping, according to area Horticulture Agent, Terry Mikel. Some of these "pineapple palms" may be seen at Mesa's Pioneer Park and are quite remarkable as living sculpture. Beautiful groupings of palms trees may also be seen at these locations, showing how dynamic a feature they may be in landscape design, when planted in multi-columned clusters.

The real star, however, in my eyes, remains Phoenix dactylifera "Medjool," not only for its tall‹up to 80' in height‹and lean lines, but for the sugary, nutritious Middle Eastern staple they produce. Fresh Medjool dates are delectable and can be very successfully cultivated in our zone. This very same variety may be seen growing along the streets of Marrakech, Morocco. The Arboretum's original date palms were imported from the Middle East in the 19th century and it is reported that they were hung off Tempe's old Mill Avenue Bridge, dangling in the Salt River to re-hydrate before planting.


Flowering Date Palm


Date palms were cultivated commercially on date farms and by small private growers in the Valley of the Sun, breaking up the low horizon line of the many citrus orchards in the burgeoning metropolis. These were planted from the turn of the century into the 1930's. One early Arizonan remembers her grandmother climbing up a tall, rickety wooden ladder with a broom and a flower spray to pollinate the family date palms trees they grew to supplement their citrus and egg money.


New growth emerges


Both male and female trees are needed for date production, and Ballard explains that the traditional Old World method of horticulture to ensure pollination included planting small female trees around a larger male tree. Examples of this planting may be seen in front of ASU's University Club or on Tyler Mall, by the Engineering College.

According to Ballard, there are several steps required for good date production, the first consideration being to periodically let the trees "rest" by cutting off the flower stalks when they emerge in mid-spring. Flower production is heat-related and generally occurs in early to mid-March in the Phoenix area. Ballard advises that date palms be winter-pruned and cleaned out and fertilized in January-February. Palms are high water users, and for fruit production, give your trees regular, deep-watering throughout the production cycle.

To pollinate, cut off any variety of male flower and shake the pollen onto the female flowers. Ballard reports that the male flower has a discernibly stronger smell than the female flower. Pollination may be accomplished by climbing up a sturdy ladder, or from a bucket truck, as it is done at the Arboretum. Workers pollinating date flowers from the bucket trucks find themselves covered from head to toe in the gritty, slightly irritating pollen after a day's work, Ballard reports. Be sure to keep covered with long sleeves and pants and gloves, if you take on this task. This process should be repeated two or three times in the flowering season, and in the Old World method, the male flower branches would be left hanging in the female trees.


Dangling date sprays.


It is a good idea to use a colored string method in marking the flower bunches, Ballard recommends, to indicate a pollination record, i.e., blue for the first time, red for the second, yellow for the third. Two or three pollination sessions are usually done, because the flowers bloom progressively, like fireworks. After a couple weeks, check to see if the efforts were successful, which is indicated by formation of hard, tripartite cylindrical fruit development. Eventually some of these will fall off during the date maturation process.

For better, larger date production, Ballard recommends finger-rubbing off every other developing date when they resemble creamy-colored pearl-sized strands, by the end of April to early May.

By the end of July and into August, the date crew is back up in the trees, covering the developing dates with paper, mesh or cloth‹never plastic‹covering the developing dates and protecting them from hungry birds. There is a harvest window from late August until the beginning of December, though the later harvest results in drier fruit. Ballard reports that dates ripen like bananas, going from a yellow "kahil" stage, and then into a brown at the peak of ripeness. Ripe fruit is a caramel-brown color and is either hand-picked or bunch-cut, when some of the dates are a little brown. Bunch cut dates are then placed on racks to continue ripening. In processing ripe dates, they are rinsed in water and allowed to sun-dry on black plastic. Occasionally, there is a black fungus on the dates, which can be seen on the date end and will result in a mildew-tasting fruit. Also, rarely ‹ in trees that are closer to the ground‹tiny, sucking insects, like spider mites, may be a problem.

Dates may be dried or may be kept in the freezer for up to a year.

Arboretum Palmae Collection:

If you would like to see the incredible assortment of palm tree varieties in one place, it might be worth your while to visit The Arboretum at ASU, which is open to the public seven days a week, dawn to dusk, and free of charge (www.azarboretum.org). For those looking for a tropical accent, there are some lovely selections to see. Smaller scale palms, like Chamadedorea elegans, Parlor Palm, or Caroyota ochlandra, the Canton Fishtail Palm, are on display, along with Phoenix roebelenii, Pygmy Date Palm, a Laotian native which gives a nice tropical effect, growing to 6' in height. Other notably attractive palm trees include the dramatic Archotophoenix cunninghamiana, King Palm, with a smooth green trunk, pink to purple flowers and a height of 50' and spread of 10-15'.

Unusual date palms include the small scale Chamaerops humilis, Mediterranean Fan Palm, which is a hardy container plant and fast growing. It produces small, shiny black fruit around its trunk, which might be a little messy, but interesting. Phoenix canariensis, the Canary Island Date Palm, has pretty tropical fronds with a heavy, scaled trunk, with inedible dates. Phoenix reclinata, Senegal Date Palm, is considered to be very desirable in the landscape because of its attractive use in many-trunked grouping. Sabal texana, Rio Grande Palmetto, a Texas native, also produces an edible fruit.

Though commonly called a "palm," there is also Cycas revolute, Sago Palm, of various sizes on display. This Palm "imposter" is really an early cone-bearing cycad and is exceptionally slow growing, with more of a Palmae appearance the older it becomes.

Photos by Janice Austin.


Maricopa County Master Gardener Volunteer Information
Last Updated November 21, 2004
Author: Lucy K. Bradley, Extension Agent Urban Horticulture, University of Arizona Cooperative Extension, Maricopa County
© 1997 The University of Arizona, College of Agriculture and Life Sciences, Cooperative Extension in Maricopa County
Comments to Maricopa-hort@ag.arizona.edu 4341 E. Broadway Road, Phoenix, AZ 85040,
Voice: (602) 470-8086 ext. 301, Fax (602) 470-8092