Monthly Archives: June 2016

Flowering and Its Trigger in Genus Agave

Agave parryi with both secondary and tertiary peduncles and the elongated yellow anthers 'floating' above.

Agave parryi with both secondary and tertiary peduncles and the elongated yellow anthers ‘floating’ above, in Sedona, Arizona.  From  americansouthwest.net.

 

 

As gardeners we come to know our plants, what to expect from them over time, how we can better meet their requirements,  and their contributions to the garden.  If we watch we learn when to expect their spring time resurgence, the extension of stems and unfurling of leaves.  We anticipate their flowering often recomposing vignettes to best display them.  They teach us over time.  But with Agaves their flowering is so infrequent, that if we don’t study them in mass over a span of years, we won’t know what to expect.  With some it can take as few as six years, some even less, while others will keep us waiting for 30 or more.  When we buy a year old grafted Magnolia we are told to be patient and we understand that the tree will take some time to grow and mature.  So we wait knowing that once it begins a Magnolia will increase in both size and floral performance rewarding us for many years to come…but with Agave, it is once and done.

Agaves are flowering plants, Angiosperms.  Angiosperms all share a broad survival strategy forming complete flowers which produce seed which grow into juvenile plants.  If you follow plants back in time you’ll that find that plants can be broken down into a few large groups.  The largest such group, the Angiosperms or flowering plants, are also the most recent of these…and the most successful.   Angiosperms have seeds encased in a ‘fruit’ that formed within the flower from the ovary.  Gymnosperms, produce seed as well, though their’s are ‘naked’ without a covering fruit, as the plants have no ovary nor true flower. There are other differences between them as well both structural and in the details of their reproductive cycles.  Other plants like ferns don’t produce seeds at all and instead rely on the more ancient process of reproducing directly from spores which grow into an intermediate form, a gametophyte, with one set of chromosomes.  This is the ‘sexual’ stage, either male or female, which mature independently, the male form later fertilizing the female, the product of which grows into the sporophyte, with two sets of chromosomes.   The sporophyte later releases the single sex, single chromosome spore that will grow into the gametophyte, continuing the cycle.  Agave, as a genus, share much with other Angiosperms, they have several distinct peculiarities they share amongst themselves as well.  They are all perennial taking more than a year to mature and flower.  This is a very common attribute.  What sets them apart is that they are monocarpic, they die after flowering once, and, they can take up to 30 years or better, depending on species and growing conditions, to flower.. Continue reading

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