Saguaro
Wind-blown saguaro, probably about 30 years old. Sagging and tapering of branches, perhaps in response to frost damage. The main stems of saguaros are supported by woody ribs, on the outside of which is a thick cortex of succulent, water-holding tissue and a thick epidermis to prevent water loss.
The ribs of the stem are heavily spined, with a characteristic pattern of spines arising from each areole. Base of a saguaro broken by wind, showing the succulent cortex surrounding the woody skeleton. Woody ribs of a dead saguaro. Saguaros flower in spring, producing many buds near the tops of the stem and main branches.
The bell-shaped flowers are about cm wide, and are visited by bats, bees and doves. When pollinated, they give rise to succulent fruits, each about 8 cm long, which split open to reveal a red, juicy pulp containing up to small, black seeds.
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These fruits and seeds are eaten readily by many birds, mammals and insects. Seed dispersal is achieved mainly by birds Gila woodpecker, white-winged doves, house finches , which each the pulp and deposit the seeds in their faeces. The tendency of these birds to perch and defaecate on the branches of trees helps to ensure that the seeds are deposited at the base of nurse plants. The seeds germinate rapidly about 5 days in response to late-summer rains, but only a very small fraction ever give rise to seedlings that survive the early years.
Long-nosed bats also feed on the fruits, but they defaecate while flying or in their roosts, so they are thought to be of little significance in regenerating seedlings. Flowers and flower buds on the ribs at the tips of stems. For many years it has been assumed that bats are the major pollinators of saguaros, because the flowers have all the features characteristic of bat pollination - nocturnal opening of the buds although they remain open through to midday , heavy scent, copious nectar, etc.
However, studies in which individual flowers were caged to exclude different types of pollinators in either night or daytime suggest that bees may be the more important pollinators - at least in some study sites. Saguaros have hundreds of flowers that bloom several per day from late April to early June.
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The flowers open at night and close the following afternoon. Lesser long-nosed bats visit the flowers at night.
Birds, mostly white-winged doves, and insects, mostly honey bees, visit the flowers the following morning. The fruits mature in June and early July. The rind splits into three or four sections that peel back to expose the juicy red pulp embedded with up to 2, tiny seeds.
The fruits ripen during the peak of drought in the early summer and are about the only moist food source for many birds, mammals, and insects during this part of the year. Saguaros make excellent nesting places for many birds.
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Gila woodpeckers and gilded flickers both excavate nest holes in the fleshy stems. The woodpeckers usually excavate new nest holes each year giving other birds like elf owls, house finches, ash-throated flycatchers, and purple martins an opportunity to occupy old woodpecker nests. Red-tailed hawks and other large birds nest in the angles between the main stems and the arms. Tall saguaros make good hunting and resting perches for many birds.
Saguaro flowers, Scottsdale, Arizona. Unusually-formed crested or cristate saguaro near Kino Bay , Sonora. From Wikipedia, the free encyclopedia.
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This article is about the cactus. For the baseball team, see Surprise Saguaros. This section needs expansion. You can help by adding to it.
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Retrieved 24 April Loss of the ndh gene suite and inverted repeat". American Journal of Botany. Sonoran desert columnar cacti and the evolution of generalized pollination systems. Band 71, Number 4, , pp. Bird tracks and sign. Cavities in saguaro cactuses in the Southwest are common. Both gilded flickers and Gila woodpeckers make these cavities for nesting, but they often choose different locations on the cactus. The stouter bills of the gilded flickers allow them to cut cavities through the wooden ribs near the top of the cactus where the ribs converge. Gila woodpeckers stay at midlevel on the cactus where the ribs are separated enough to cut a cavity between them.
Cavities in saguaros are cut out by these birds the year before they are inhabited. The excavated cactus secretes a fluid that hardens into a scab, thus preventing water loss, which could kill the cactus, as well as waterproofing the inside of the next cavity. Although they do not use them immediately, waiting first for the sap to harden, Gila woodpeckers excavate cavities in cacti and trees as nesting sites. Females typically lay two broods a year of three to five eggs, which incubate for 14 days. Once abandoned, the cavities are occupied by reptiles, rodents, and small birds like kestrels, elf owls, flycatchers, and wrens.
In the desert, the woodpeckers perform the important ecological function of removing unhealthy flesh from the saguaro cactus. Some insects on which it feeds carry diseases, harmless to the bird, which damage the cactus and leave discolorations. The marks signal larvae to the bird, and as it excavates the insects, it also cuts away the diseased tissue. As the sap hardens, the cactus is healed, and the excavation becomes a convenient nesting site. Arizona Department of Agriculture.
Archived from the original on September 20, Archived from the original PDF on September 20, Destruction of protected plants by private landowners; notice; exception".
- Saguaro Cactus Fact Sheet!
- saguaro - Wiktionary;
- Plant Fact Sheet: Saguaro Cactus.
Retrieved July 2,