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Index : Landscape Plants
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- 27. Cycads - Ancient Plants for Tucson Gardens - Top
- During the age of the dinosaurs a group of plants we know as cycads were the most abundant plants on Earth. Some of these true living fossils are amazingly still with us today having survived for some 200 million years due, in no small part, to their toughness and adaptability. Fortunately, our winters are mild enough to allow us grow several types of cycads in our gardens and landscapes here in Tucson. While our summers are certainly not mild, these tough plants can tolerate the desert heat and dry air.
Cycads are palm-like, cone-bearing evergreen plants dating back to the Jurassic Period. They are represented by three families - Cycadaceae, Stangeriaceae, and Zamiaceae, presently composed of 200 species in 11 genera - Bowenia, Ceratozamia, Chigua, Cycas, Dioon, Encephalartos, Lepidozamia, Macrozamia, Microcycas, Stangeria, and Zamia. Even though there are 200 species, a limited number of those are cultivated and available to gardeners. These cultivated species are mainly in the Cycas, Ceratozamia, Dioon, and Zamia genera.
Cycads are dioecious plants, which means that plants are either male or female. Female plants produce seeds and male plants produce cones full of pollen. Seeds on many varieties are bright red and very showy.
Probably the most popular and commonly grown cycad is Cycas revoluta, the King Sago or Sago Palm. Although cycads bear no relationship to palms, some such as Sago carry the moniker "palm" because their appearance is so suggestive of a palm. They typically have long, graceful compound leaves, called fronds, that spread out from the top of a single trunk.
Cycas revoluta, a member of the Cycadaceae family, has long dark-green feather-like leaves that grow in a rosette fashion form the base of the plant. Young plants have a spread of 3 feet, but in time the canopy can expand to 6 feet or more across. With age, a stout, dark brown trunk develops, adding to the plants landscape appeal. Sagos are often used as a primary component in Japanese garden design. They also provide striking accents in Mediterranean-styled landscapes.
As with other cycads, C. revoluta is tolerant of a wide range of soil conditions and is quite tolerant of our highly alkaline desert soils. It tolerates temperatures down to 20 F. and is one of the most cold-hardy of the cycads. In the desert, C. revoluta along with other cycads should be located where they receive some mid-day and afternoon shade. Or they can be grown in full shade.
Occasionally, C. revoluta will develop a deficiency in manganese which causes brown spots to develop on new growth. This is easily prevented by misting the newly emerging leaves with a solution of one teaspoon of manganese sulfate in a pint of water. It's a good idea to the manganese solution with the emergence of each new set of leaves just as a precaution.
Another cycad highly recommended for the Tucson area is Dioon edule, a member of the family Zamiaceae. Dioon has light, bluish-green fern-like leaves, more delicate in appearance than C. revoluta. A native of Mexico, Dioon's delicate appearance belies it's tolerance to extreme heat and to cold down to 17 F.
All cycads lend themselves to growing in pots, and it's a way to cultivate some of the more cold-sensitive types here in Tucson. For instance, Zamia maritima (formerly Z. furfuracea) is a striking container plant but it's injured at 28 F, so being able to move it to a warmer location during winter cold snaps is a solution.
Zamia maritima is also called the Cardboard Palm, because of it's interesting broad, stiff leaves that feel just like cardboard. This cycad stays small in a container with a spread of 3 feet or less. Male and female cardboard palms both produce interesting reproductive cones. Females bear an aggregate cone with bright red seeds.
Other relative cold hardy and desirable cycads include; Zamia pumila (Coontie), Ceratozamia robusta, and Ceratozamia latifolia. Check with local nurseries for availability of some of the more common cycads. For additional hard-to-find types there are several specialty Cycad nurseries in California that can be located through an internet search for "Cycads".
"Selection, Planting & Care of Desert Trees" will be the topic for this week's garden demonstrations. They will be presented on Wednesday at 9 a.m. at the Pima County Extension Center, 4210 N. Campbell Ave (central); and at 1 p.m. at the Wilmot Library (east), and on Friday at 1 p.m. at the Oro Valley Public Library (northwest).
Written by John Begeman, College of Agriculture and Life Sciences, the University of Arizona, 520-626-5161. - Updated: March 7, 2004
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