Tom Karwin, On Gardening | Aeoniums and other winter growers

Peninsula Premier Admin

Care for your garden

Even during these cold and bleak winter months, some succulent plants are going through their primary growth period. The “winter grower” (or “summer dormant”) succulents include several popular genera that you might have in your garden: Aloe, Cotyledon, Crassula, Dudleya, Gasteria, Haworthia, Kalanchoe, Pelargonium, and Sedum.

These plants should be allowed to rest during the summer months. When they are in growth mode from November to March keep them well-irrigated. Seasonal rains usually provide these plants with ample moisture to support their growth, although periods of drought could call for supplementary irrigation.

I write this column while anticipating exceptional rainfall, but we could also have dry conditions during this winter.

Let’s consider one of the more popular winter growers: the Aeonium. This genus includes 35–40 species (depending how they are counted), most of which are native to the Canary Islands, which is off the west coast of North Africa. There are also growing numbers of hybrid cultivars.

The rosette’s fine red edge adds to its appeal. (Contributed)
The Aeonium’s flowers are winter time welcomes but its rosettes are the main show. (Contributed)

The Aeonium species include a range of sizes and colors, all with a winter growth cycle. They also have many common characteristics: attractive rosettes of leaves, preference for partial shade, easy cultivation and propagation, and a requirement for well-drained soil.

Aeoniums produce attractive flower clusters during their winter growing phase. Most Aeoniums are monocarpic, meaning that the flowering stalk dies after blooming. If the plant has produced side shoots, those side shoots will live on.

One of the more common species, Aeonium arborescens, reaches or exceeds 3 feet in height, and tends to develop rangy growth, with rosettes on the end of ever-lengthening bare stalks. A. arborescens has green leaves, with some varieties edged in red. A popular variety of A. arborescens is ‘Zwartkop’, with very dark, almost black rosettes.

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 the stalk in an appropriately semi-shaded and well-drained location.

A good practice for this propagation 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 propagation method could be applied to any Aeonium species that become more rangy or “leggy” than the gardener prefers.

Some species of this plant tend to be naturally more shrub-like. A. canariense, for example, has a lower growing, branching structure that doesn’t require regular cutting and replanting.

Another example, A. ‘Kiwi’, a hybrid of Aeonium haworthii, has smaller rosettes and grows to just 2–3 feet high and wide.

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 a fine 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 most other herbaceous plants, as well.

It is difficult to change a garden’s natural soil, 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 create 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 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 happen to have access to a quantity of inorganic rubble, e.g., broken concrete, rocks, etc., you could place it under the planned mound to support quick drainage of moisture. Plan to provide enough soil on top of this foundation for root growth.

As an aside, the concept of the rock garden 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 actually increase the potential planting area.

If you have a difficult gardening situation and a long-term vision for gardening success, consider a mound-building project.

Advance your gardening knowledge

There are growing online resources to draw upon as you advance your gardening knowledge. While live webinars have particular appeal, many recorded presentations are worthy of your time. Ideally, you can select and view talks or demonstrations that address your specific interests and priorities.

I have often recommended searching for topics of your current interest, but that extraordinary resource includes varying levels of gardening expertise and production value, so it presents a “viewer-beware” situation.

More consistently trustworthy resources are the video archives of gardening organizations and publications. Those presentations have been screened by editors who ensure the quality and reputations of the sponsors.

Here are opportunities to explore:

New York Botanical Garden ( ): Click on “What’s On” or “Read & Watch”The Impatient Gardener ( Click on “Videos”Garden Design ( Click on any menu item of interest, including “Online Classes” (fee-based) and “Garden Tours.”

Fine Gardening ( Clink on “Videos.”

Huntington Botanical Gardens (

There are many more online resources, including some from England and Europe that we’ll check out in future columns.

Enrich your gardening days

Don’t let wintry days keep you from your garden. There are always opportunities to pursue and rewards to gather. Although it changes with the seasons, your garden always needs your attention and offers enriching experiences.

While you’re doing that, keep your emotions positive and your viruses negative and enjoy your garden.

Tom Karwin is past president of Friends of the UC Santa Cruz Arboretum, Monterey Bay Area Cactus & Succulent Society, and Monterey Bay Iris Society, and a Lifetime UC Master Gardener (Certified 1999–2009). He is now a board member and garden coach for the Santa Cruz Hostel Society. To view daily photos from his garden, To search an archive of previous On Gardening columns, visit

Contributed by local news sources

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