Growing aeoniums for the ages - Santa Cruz Sentinel

ON GARDENING

Growing aeoniums for the ages

Kiwi aeonium (Aeonium haworthii ‘Kiwi’). A variety of A. haworthii, this plant grows 2 to 3 feet high and wide, with 3 to 5-inch wide rosettes of variegated leaves, with deep shades of yellow and green. When grown in the sun, its tips are crowned with brilliant red, giving it the common name tricolor or dream color. It grows actively but slowly during the winter and spring, and goes dormant during the summer, requiring little to no water. PHOTOS COURTESY TOM KARWIN

Copper pinwheel (Aeonium ‘Sunburst’). A bold and colorful cultivar with 6 to 8-inch wide rosettes variegated with green, white and yellow, and a pink leaf margin. This succulent grows 1 to 2 feet high and 2 to 3 feet wide. This image shows that during the winter, new growth appears in the rosette’s central core. Tiny, tightly packed leaves are vivid cream, green and sometimes a touch of pink at the margins.

Black rose aeonium (Aeonium arborescens ‘Zwartkop’). This cultivar of A. arborescens forms clumps of 3 to 4 feet tall gray-brown stems that branch near their base, with large terminal rosettes of very dark purple leaves. It grows in winter and is semi-dormant in summer when it forms yellow star-shaped flowers in conical clusters from the center of the rosettes. The stems bearing the flower then die to the ground.

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Care for your garden

We focused recently on whether to prune trees and shrubs in January or wait until late winter/early spring. This decision is based on the plant’s bloom time.

Let’s consider one of the winter growers: the aeonium. This genus grows easily and well in the Monterey Bay area, and includes a broad range of forms, sizes and colors, earning its status among the most popular succulent plants.

The genus aeonium includes 35 to 40 species (depending on how they are counted), most of which are native to the Canary Islands, which is off the west coast of North Africa. These islands are in the Atlantic Ocean, not within the Mediterranean Sea, and are within the Mediterranean climate zone.

The generic name of these plants is based on the Greek word for “ageless.” The English word aeon is a variant of eon, meaning “a period of time.”

Wikipedia has a list of aeonium species (en.wikipedia.org/wiki/aeonium). While some species have been established in gardens, many cultivars and hybrids are available to gardeners wishing to collect many different varieties.

Today’s image gallery includes examples of aeoniums growing in my garden.

Aeoniums include a range of sizes and colors. They also have many common characteristics: attractive rosettes of leaves, a preference for partial shade, easy cultivation and propagation and a requirement for well-drained soil.

Aeoniums’ active growth period is during the winter, the year’s darkest days. During this period, the plants require hours of full sunlight.

The plants develop attractive flowers during winter and bloom in clusters during late winter or early spring. Most aeoniums are monocarpic, meaning that the flowering stalk dies after blooming. The plant could branch or offset to produce multiple rosettes. Each rosette produces a central inflorescence and then dies back. If the plant has produced side shoots, those side shoots will live on.

Stalkiness is the plant’s natural growth, but some gardeners prefer a more compact structure. They can promote a tighter form by lopping off the rosettes with a few inches of stalk and replanting it in an appropriately semi-shaded and well-drained location.

A good practice for this propagation is to allow the stalk’s cut end to dry (“callus”) for a few days before planting. This method reduces the potential for the stalk to rot when it comes in contact with the soil’s lively population of microorganisms.

This technique could be applied to any aeonium species that become more rangy or “leggy” than the gardener prefers.

Planting on mounds

Aeoniums, like other succulent plants, grow best with only occasional moisture. By definition, succulent plants have evolved to store moisture in their roots, stems or leaves, and do not do well in soggy conditions. If your garden bed is well-drained due to loamy soil and sloping terrain, you have an acceptable environment for succulent plants.

Some gardens, however, will have a flat profile and a high percentage of moisture-retentive clay soil. Or, a garden will have a low area that collects rainwater and becomes soggy. In either case, the bed is inhospitable to succulent plants and herbaceous plants.

Changing a garden’s natural soil is difficult, but the practical solution to poor growing conditions is to develop raised beds. These might be called mounds or berms. They might also be called “Mediterranean mounds” because they are well-suited to plants from that area of the world. Of course, elevated garden beds are not unique to that region.

Creating mounded garden beds is not a trivial task. It usually involves importing enough soil of good quality (“topsoil”) to make the desired growing conditions. Such soil is available from local suppliers of landscape and building materials and can be delivered by the supplier or transported by a friend with a pick-up truck.

How much is enough? That depends on your height, width and length objectives. The height of your raised bed should be enough to support the roots of the plants you will install. Provide enough height to avoid heavy clay or soggy soil.The width and length of the mounded bed(s) will depend on the available space, your aesthetic vision and the amount you want to commit to the project.

The ideal shape of mounded beds depends on your unique situation. Generally, gently curved beds are better than straight beds, but that’s a matter of personal preference. Sketches of the area to be improved could stimulate creative planning.

If you can access a quantity of inorganic rubble (e.g., broken concrete, rocks, etc.) you could place it under the planned mound to support quick moisture drainage. Plan to provide enough soil on top of this foundation for root growth.

As an aside, the rock garden concept has different objectives than a raised bed to support plants that require excellent drainage. We could explore rock gardening in a future column.

The one-time cost of creating mounded garden beds will create excellent growing conditions (the primary purpose), add an attractive third dimension to the garden and increase the potential planting area.

Consider a mound-building project if you have a problematic gardening situation and a long-term vision for gardening success.

Consider including aeoniums as a striking highlight or a collection of unique cultivars in your garden.

Advance your gardening knowledge

The American Horticultural Society has announced the winter series of its online Lifelong Learning Program, launching in mid-January. The program includes four series: Horticulture & the Environment; Garden Design & Techniques; Plants, Culture, & Community; and Behind-the-Scenes Garden Tours.

Here are January’s programs:

• The Perennial Plant Collector’s Treasure Chest with Kerry Mendez, principal and founder of Perennially Yours. Friday, Jan. 17, 2 to 3 p.m.

• Lawn Alternatives and Organic Lawn Care with Paul Tukey, author and director of regional partnerships, Glenstone Museum. Thursday, Jan. 23, 7 to 8 p.m.

• Plants in Southern Food History with Terri Carter, educator, University of Georgia Extension. Friday, Jan. 24, 2 to 3 p.m.

• Edible and Medicinal Perennials for Your Garden with Linda Black Elk, education director, North American Traditional Indigenous Food Systems. Thursday, Jan. 30, 7 to 8 p.m.

Participation in these programs requires a registration fee of $15 (members) or $20 (non-members). For information and program registration, visit the American Horticultural Society website (ahsgardening.org/ahs-lifelong-learning/ahs-live-2).

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 & Succulent Society and a Lifetime UC Master Gardener (Certified 1999-2009). He is now a board member of the Santa Cruz Hostel Society, and active with the Pacific Horticultural Society. To view daily photos from his garden, facebook.com/ongardeningcom-56651 1763375123. For garden coaching info and an archive of previous On Gardening columns, visit ongardening.com.