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How old can some Dioon and Macrozamia cycads be?
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Cycadophyte
Cycas circinalis.
It has been estimated that some cycads, particularly those in the genera Dioon and Macrozamia, may reach up to 1,000 years of age.1
Because these plants lack annual growth rings, scientists determine these age estimates by counting the whorls of leaf scars on the stem, which correspond to the plant's annual or biennial production of new leaf flushes. However, it is considered doubtful that most cycads reach such an advanced age.1