Mangave ‘Lavender lady.’ (Courtesy Tom Karwin)
Mangave ‘Purple people eater.’ (Courtesy Tom Karwin)
Mangave ‘Bloodspot.’ (Courtesy Tom Karwin)
Sims aeonium x Canary Island aeonium (A. simsii x A. canariense). (Courtesy Tom Karwin)
Aeonium ‘Floresens’. A mutated cultivar of the pinwheel aeonium (A. haworthii). (Courtesy Tom Karwin)
Black rose aeonium (A. ‘Zwartkop’) and tree aeonium (A. arborescens). (Courtesy Tom Karwin)
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Mangave ‘Lavender lady.’ (Courtesy Tom Karwin)
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All gardens occasionally benefit from a substantial work-over. In today’s column, I describe such a project in my garden.
In brief, the project basically involves exchanging two groups of plants. There are several related changes, as well. Larger-scale projects can include several smaller-scale components.
Today’s image gallery
This project involves two very different genera: mangave and aeonium. The garden has several cultivars of each genus, and the accompanying images include examples of each.
The need to move the mangaves
Mangaves are hybrids of agave and manfreda species. Both are Mexican natives that have hybridized naturally, and growers have combined various species to create interesting mangave cultivars.
Mangaves previously were regarded as separate genera within the agavoideae, a subfamily of the asparagus plant family (Asparagaceae), and are now listed as species within the agave genus. Check it out by browsing to en.wikipedia.org/wiki/Manfreda.
Mangaves resemble the familiar agaves. They are symmetrical, drought-tolerant succulent plants that tend to be more compact than agaves, with softer leaves and spines.
They resist high temperatures and direct sunlight, and generally prefer shaded areas. According to other reports, increased exposure to ultraviolet light from the sun causes the plants’ foliage colors and patterns to become more pronounced. Less light will result in faded coloring.
The Monterey Bay area provides little hot, intense sunlight, where mangaves will develop nicely with full sun exposure in this temperate climate.
My mangave collection was on the patio, in containers. I had established it in filtered sunlight, but over time, the adjacent chitalpa tree grew, increasing the shade over these plants, and they were not flourishing. We should move them for greater exposure to the sun.
The challenge was to find a suitable location in the well-planted garden, which had no empty, sun-filled spaces.
The need to move the aeoniums
Most aeoniums are native to the Canary Islands in the Atlantic Ocean, located 62 miles northwest of the African continent. These islands are outside the Mediterranean Basin, but they have a Mediterranean climate, characterized by cool seasons and dry summers. Due to the ocean’s influence, the climate environment of the Canary Islands is like that of Southern California.
My garden areas represent each of the world’s five Mediterranean climates, with two beds for plants from the Mediterranean Basin. The growing collection of aeoniums has dominated one of these beds.
The aeoniums have overgrown, making their bed jammed with plants. The bed needs renovation.
The bed has full exposure to the sun. Most reports on the internet consistently state that these plants tolerate full sun and prefer shade. Other reports, however, call for full sun, indicating that they are best suited to mild Mediterranean climates. Filtered sunlight in the temperate climate of the Monterey Bay area should be acceptable.
So, moving the aeoniums to the filtered shade on the patio (where the mangaves are now) would clear the aeoniums’ sun-filled bed for the mangaves.
Aeoniums grow in the winter and are dormant in the summer. The best time to move them is in the fall, just before their growth period. However, moving them in the summer should also be workable. Relocating the plants can be done easily by cutting and replanting the rosettes.
Removing mangaves from the patio’s eight or nine large containers will provide separate homes for different Aeonium cultivars. We can prune them occasionally to control their size, as needed.
The change process
Relocating the aeoniums to create space for the mangaves can be done in phases: lifting some mangaves, then planting some aeonium rosettes.
That’s the basic process, but we also need to remove the other Mediterranean plants from the sunny bed. These include four or five English lavenders, a clump of Iris spuria ‘Always a mystery,’ and a globe daisy (Globularia sarcophylla ‘Blue eyes’).
We can move the English lavenders to the remaining bed for Mediterranean Basin plants. We could remove some overgrown euphorbias to create space.
Most recommendations schedule transplanting lavenders in spring or early fall, but some call for summer as the “perfect” time for transplanting, as it provides time to establish in a new environment before colder temperatures begin. Transplanting now is convenient for our project.
The globe daisy should have a prominent space to display its appealing blossoms. We decided to install this small shrub in a large container in a full-sun area of the patio. The plant has finished blooming, so now is a good time to move it. The lavenders had crowded this plant, causing abnormal development, so we will prune to improve its form.
The iris spuria should have been divided every three or four years, but it had been growing much longer in place and developing a vigorous 4-foot-tall clump with limited flowering. The task is to cut it to the base and divide the rhizomes for replanting.
Growers should replant the rhizomes two feet apart to allow room for growth. When we lift the rhizomes, however, we will have far too many to replant in the available space.
Iris spuria is not an iconic plant of the Mediterranean Basin. According to Wikipedia, “Iris spuria is native to a vast area, from Africa, to temperate and tropical Asia and Europe.” When we chose to plant it in a Mediterranean Basin bed, we applied an overly liberal interpretation of nativity.
Now, our decision is to offer the rhizomes to members of the Monterey Bay Iris Society.
The intended results
Exchanging mangaves and aeoniums and finding homes for the other plants requires a good amount of effort. The two sites have differently sized areas, so we will display the mangaves in a well-spaced arrangement and control the growth of the aeoniums. I’ll display the results in a future column.
This week in the garden
We describe our plant exchange project to provide an example of working through a substantial renovation, and suggest readers consider the need for such a project to reinvent or improve part of their garden. Larger-scale projects can take time and planning to ease the task.
Mark your calendar
The August meeting of the Santa Cruz County Chapter of the California Native Plant Society will feature Cabrillo College horticulture instructor Nicky Hughes. She will lead a tour of the California Native Plant Society’s propagation area in the horticulture area and showcase the new native plant landscape project at the college’s main classroom building.
This event will convene on Aug. 11, beginning with a keying session at 6 p.m. and the meeting at 7 p.m. The Society will hold the event at the Horticulture Building, at the top of the campus, 6500 Soquel Drive, Aptos.
For more about the Santa Cruz County Chapter of the California Native Plant Society, browse chapters.cnps.org/santacruz.
Enjoy your garden!
Tom Karwin is a past president of Friends of the UC Santa Cruz Arboretum and the Monterey Bay Iris Society, a past president and lifetime member of the Monterey Bay Area Cactus and Succulent Society, a Lifetime UC Master Gardener (certified 1999-2009), past board member of the Santa Cruz Hostel Society and active with the Pacific Horticultural Society and other garden-related societies. To view photos from his garden, visit facebook.com/ongardeningcom-566511763375123. To review the archive of recent On Gardening columns, visit santacruzsentinel.com and search “Karwin.” Go to ongardening.com to review columns from 2012-2020 (and soon) from 2025. Send comments or questions by email to gardening@karwin.com.