This is the time of the year when agaves bloom. Let’s review how they propagate.
Agaves are popular plants for gardeners because of their range of sizes, colors and leaf forms. I have been collecting agaves for some time and have been fascinated by their variations as well as their common characteristics.
Agaves, which are native to Mexico, Southern United States, or South America, grow well in the Bay Area’s climate.
Most agave species have defensive spines — terminal or marginal spines or both — that can be quite sharp. Some gardeners are “agave-aversive,” for fear of being poked. Their self-preservation priorities are leaving attractive plants out of their gardens.
Agaves can be safely grown placed away from walkways, weeded as needed with garden tongs, and transplanted while wrapped in a towel. These techniques are not needed with most other garden plants, but they open the landscape to an interesting group of plants.
The Agave is a very old and fairly large plant genus that taxonomists divided a few years ago into three sub-genera: agave, littaea, and manfreda.
The relatively recent agave x manfreda hybrids yield mangaves, which combine their parents’ characteristics and provide a diverse new category of desirable garden plants. Manfredas typically lack spines, so mangaves do as well, and can be appealing to agave-averse gardeners.
The littaea sub-genus is similar to—and older than—the agave sub-genus. These two sub-genera have one significant difference, which comes up later in this column.
The two-way propagation of agaves.
Most agaves propagate through rhizomatous growths, which are called offsets or “pups.” They typically grow closely under the mother plant, forming tight clusters. The gardener can separate the pups from the mother and either replant them either nearby to create a colony or in another location, or make them available to other gardeners. They transplant easily.
Some agaves, called solitary, do not produce offsets. Some gardeners prefer off-setting species, others prefer solitary species.
All agaves also propagate by producing a striking flower stalk that emerges from the center of the plant’s rosette. The stalk’s height varies with the species, ranging from 6 feet to as much as 40 feet.
The stalk develops into an inflorescence, a cluster of greenish-yellow flowers on individual stems. Some agaves have orange or red flowers.
There are two architectures of the agave inflorescence, depending on the sub-genus.
The littaea sub-genus produces a raceme, which is an elongate, unbranched, indeterminate inflorescence. Plants that have racemose inflorescences include foxtail agave (A. attenuata), octopus agave (A. vilmoriniana), and queen of white thread century plant (A. schidigera). I have specimens of these plants in my garden, but none are in bloom, so today’s column includes an example of this sub-genus from Wikipedia Commons.
The agave sub-genus produces a branched raceme, called a panicle. Plants that have paniculate inflorescences include the prominently large century plant (A. americana), which attracts attention when it blooms, and the variegated Caribbean agave (A. angustifolia var. marginata), now in bloom in my garden.
While agaves tend to bloom in the late summer, not all of these are in bloom at the same time. That’s because they take different numbers of years before producing a flower stalk, with the time ranging from six-to-eight years (e.g., A. tequilana, A. angustifolia) to about 30 years (e.g., A. Victoria-reginae). The century plant’s common name implies an even longer time for it to bloom, but it really takes about 15 years.
Once an Agave blooms and produces bulbils, it dies. This kind of plant is monocarpic. (Plants that produce several generations of seeds or bulbils are polycarpic.)
It might seem sad to see an attractive and sometimes large plant shrivel. Still, after the plant invests its energy into growing its flower stalk, it topples to the ground and releases its new generation: a substantial number of bulbils that root on their own.
Agaves are fascinating plants for their varied appearances and their two propagation methods—routine and ultimate—add to their performance in the garden.
Advance your gardening knowledge
To learn more about agaves, visit Wikipedia.com and search for “agave” or “List of agave species.” These lists regretfully are not divided by sub-genera.
Another helpful resource is Debra Lee Baldwin’s Agave page, available at debraleebaldwin.com/agave-photos-labeled-identified. It includes a gallery of agaves for identification.
An excellent book by Jeremy Spath & Jeff Moore is “Agaves: Species, Cultivars & Hybrids” (2021). This large volume, which includes hundreds of photographs and knowledgeable notes, is a valuable reference for the avid grower of agaves.
The Cactus and Succulent Society of America will present the webinar, “Tricks and Tips for Propagating Succulents,” at 10 a.m. Sept. 3. The presenter, Ernesto Sandoval, is the manager and curator of the Botanical Conservatory at the University of California, Davis. He is an enthusiastic grower of succulents who has deep knowledge of these plants.
Enjoy your garden!
Tom Karwin is past president of Friends of the UC Santa Cruz Arboretum and the Monterey Bay Iris Society, a Lifetime Member of the Monterey Bay Area Cactus & Succulent Society, and a UC Master Gardener.
Source: www.mercurynews.com