Designing a Succulent Garden

The recent surge of interest in gardening with succulent plants combines the appreciation of colorful plants with architectural interest, drought-tolerance, and ease of maintenance.

Succulent plants are often grouped in the landscape because they share a preference for limited irrigation. This approach, called “hydrozoning,” simplifies watering tasks, and, conversely, avoids accidentally over-watering succulents.

This emphasis on the design of irrigation plans often results in garden designs that consist entirely of succulent plants. This approach can produce interesting “desert landscapes” that compare and contrast the range of colors, forms, and textures of the plants. The plants might be spaced widely or clustered closely.

Examples of such landscapes can be viewed at these websites: https://tinyurl.com/y7kclnee and https://tinyurl.com/y8vhzje4.

Succulent plants, by definition, are native to places with limited moisture: sandy deserts, rocky mountainsides, and plains that have extended periods of drought and occasional downpours. A desert landscape design will be most successful aesthetically when the plants are in fact native to a similar dry environment. Two basic styles are the rock garden, simulating a mountainside, and a desert-like sandy or gravelly bed,

A second consideration in planning such a landscape is to focus on plants from the same geographic region. While succulent plants grow in many parts of the world, the specimens that are most commonly available from garden centers and mail-order sources are from either Mexico or South Africa, with Australia as a distant third.

In the Monterey Bay area, succulent plants from all of these areas will thrive, but mixing them in a garden design often yields a haphazard appearance. The arbitrariness of the combination will be obvious to gardeners who study succulents, and subtly “off” to casual observers.

Another basic approach to the succulent landscape design involves combining succulent plants with drought-tolerant perennials. Such combinations certainly occur in nature, so an authentic design that rings true intuitively requires some research. This approach can provide interesting contrasts between relatively static succulent plants and visually active plants, such as grasses.

A third approach involves deliberately showcasing plants from a variety of native habitats. The plants used in such a landscape still need to be appropriate to the growing environment, and might require selective irrigation from a well-planned drip irrigation system, but can be educational from a horticultural perspective. An accompanying annotated garden map would add value to such an essentially educational landscape.

If you are now or might become inspired to develop a small or large landscape devoted to succulent plants, decide on a thoughtful approach, do some preliminary research, and install the landscape that fulfills your unique vision. The result is most likely to satisfying to yourself and appealing to visitors to your garden.

Gardening for the Senses

Gardeners develop and maintain ornamental gardens primarily for the visual appeal of beautiful blossoms and lush foliage. These gardens also please the sense of sight with the shapes of plants and the similarities or contrasts between plants.

Ornamental plants could also please three other of our senses:

  • Taste is served by certain plants that are both edible and ornamental, e.g., Saffron (Crocus sativus);
  • Touch is valued in plants that interesting texture, e.g., Lambs Ears (Stachys byzantina); and
  • Hearing relates to plants that rustle in the breeze, e.g., New Zealand Flax (Phormium.

There are more examples of ornamental plants that appeal to these senses, but they are minor features of the garden, relative to plants that appeal to our sense of sight.

The fifth important category of ornamental plants is the aromatic plants: those that appeal to the gardener’s sense of smell.

The blossoms or the leaves, or both, of aromatic plants, produce volatile compounds that are known as essential oils. Their primary purpose, of course is to attract pollinators, but people have found myriad culinary, medicinal, therapeutic, and even magical and uses of such plants. Books have been written about such desirable applications. Here, we focus on our enjoyment of the aesthetic appeal of aromatic plants.

Plants with aromatic foliage release their essential oils primarily during the heat of the day. When the sun goes down, the foliage must be rubbed to appreciate the fragrance.

In comparison, some aromatic flowers release their perfumes during the evening and night hours to attract moths that have evolved to reach the plant’s nectar through long corolla tubes,

Many aromatic plants produce pleasant fragrances during the daytime and can be desirable additions to the landscape. An online search for “aromatic plants” will yield the information needed to select and locate plants to optimize daytime and evening enjoyment.

For example, very popular evening-scented aromatic plants include Sweet Rocket (Hesperis matronalis), Border Phlox (Phlox paniculata), Honeysuckle (Lonicera), Evening Primrose (Oenothera biennis), Night-scented Phlox (Zalusianskya ovata), and Night-scented Stock (Matthiola bicornis).

The aromatic California native plants may be particularly interesting to gardeners in the Monterey Bay area. We appreciate the studies of Jackie Pascoe, a member of the California Native Plant Society, to select a few noteworthy plants in this large group.

  • Spice Bush (Calicanthus occidentalis) – wine barrel scent
  • Vanilla Grass (Hierogonum occidentalis) – vanilla scent
  • Fragrant Pitcher Sage (Lepechinia fragrans) – minty, but entirely unique scent
  • Coyote Mint (Monardella villosa) – minty scent
  • Wild Mock Orange (Philadelphus lewisii) – orangey scent
  • Cleveland Sage (Salvia clevelandii) – clean scent, “like a sweet desert morning”
  • Yerba Buena (Satureja douglasii) – wonderfully spicy scent
  • Catalina Perfume (Ribes viburnifoium) – fine wine scent

You could find some of these aromatic plants at the California Native Plant Society’s sale on Saturday. For info, see the story elsewhere in today’s newspaper.

Another good opportunity to learn about aromatic plants is to visit the Aroma Garden at UCSC’s Arboretum & Botanic Garden.

Explore the large and varied universe of aromatic plants to discover your preferences, and add a few to selected locations in your garden to expand your sensual enjoyment.

Right-size Plants for the Garden

While selecting plants to bring to your garden, considerations begin with basic cultural issues: exposure (sun, partial shade, full shade); moisture (infrequent; regular; ample); and drainage (fast, normal, boggy). Other more advanced cultural issues exist for future discussions.

Once we satisfy the basic cultural conditions, the selection process can proceed to aesthetic issues. There are many such issues, potentially, because they involve site-specific priorities and gardener-specific preferences. Today’s column addresses the mature sizes of plants as factors to consider when selecting a new plant for the landscape.

Plant size might seem an obvious concern, but an all-too-common error is to install a plant where it will grow eventually to intrude on a pathway, overwhelm nearby plants, unintentionally block a view, or reach over a fence into a neighbor’s space.

Such issues could arise with all kinds of plants, although some grow more slowly than others and could become a problem only after several years of maturation.

Thoughtful gardeners favor purchases of small plants, knowing that they could buy at lower cost by growing the plant themselves rather paying a nursery to care for the plant for one or more seasons. That’s a good and frugal practice for gardeners, and it brings the additional pleasure of watching the plant grow in the garden.

Garden centers often carry selections of herbaceous perennials and succulents in four-inch—and even two–inch—containers, and woody shrubs and trees in one-gallon or smaller containers. These small plants often have labels that indicate their mature size, and the gardener has the responsibility to read the label and select plants that are suitable for the space they are intended to fill.

Small plants can be misleading, however, when the label provides insufficient information about its eventual size, or when the buyer overlooks this important information. If the label doesn’t tell the story, search for the plant’s botanical name on the Internet to learn about its full size.

For example, I recently brought home a four-inch pot holding a Dasylirion longissima. The common name, Mexican Grass Tree, suggests its eventual size, which is eight-to-ten feet wide, with a flower stalk that could reach up to fifteen feet. I’m looking for the right spot to plant it.

Photo of Large Succulent Plant

Mexican Grass Tree (Dasylirion longissima) at the UC Botani cal Garden

My garden already has a Dasylirion wheeleri, a related plant that is known as Desert Spoon. This plant has already grown to its full size of three feet wide, and once developed an impressive flower spike over eight feet high. It is, however, too close to a walkway, and its leaves have saw-tooth edges that are inhospitable to passersby and the occasional weeder. I will need to bundle it before attempting to dig up and move it to a better spot.

Large plants can be excellent specimens in the garden so this “mature size alert” is not intended to discourage the use of botanical behemoths. Given enough space, big plants can be striking additions to the garden, but it’s best when the gardener knows their mature sizes before planting.

Inspiration for Next Year’s Garden

We are now one week into the fall season of the year (the autumnal equinox occurred last Friday. Now is the time to plant in preparation for the new season. In the spring, many gardeners become inspired as garden centers display flowers that have been nitrogen-dosed into bloom, but the fall is best for installing new herbaceous perennials, and woody shrubs and trees. This time is good for such tasks because the plants will have time to establish their roots during the winter months and prepare to burst into bud and bloom in the spring. As this underground growth happens, our seasonal rains (hopefully) will provide needed moisture.

Planting and transplanting involve the pursuit of landscape design visions, which makes the late spring/early fall also a fine season for touring gardens for new ideas.

The Garden Conservatory, a non-profit organization, conducts a national program of one-day garden tours, known as the Open Days program. The tours are organized in local clusters of three-to-five outstanding private gardens. The Conservatory publishes an annual catalog of Open Days events, which are scheduled from April through October.

Last weekend, I visited one of the Open Days clusters in San Jose, and volunteered as the greeter at one of the gardens. There were three gardens on tour: a garden designer’s “intensely private sanctuary” with extensive stone and cast embellishments; a design gem, once featured in Sunset magazine and recently recovered from five feet of flood waters; and an artist’s nicely designed and well-managed collection of palms, cycads, bromeliads, ferns and succulents.

I won’t attempt to describe these gardens in more detail. The direct experience is always best. These three gardens are not larger than standard city lots, and they each presented details that most gardeners could adapt for their own landscapes. They also have interesting and well-grown plants, one of which (shown below) I could not identify:

Photo of Unknown Plant in Container

Mystery Plant

This striking plant was in the designer’s garden, but he was not present when I visited. The flower resembles that of the Firecracker Plant (Cuphea ignea), but the leaves are quite different. I’m searching for its name.

Several design details caught my attention. I particularly liked the use of small black river stones (Mexican pebbles), which are available in several sizes. These can be used loosely as a stone mulch, placed in sand or concrete as decorative pavement, or in other ways as imagination might lead.

Another design detail of interest was the use of small Christmas light strings, woven into hanging metal pieces, e.g., chandelier, empty birdcage, etc. and serving a decorative lighting under a patio roof. Not everyone has a similar situation, but the effect would be attractive in the evening.

Thirdly, I was impressed by the use of very large carved stone, natural stone, and cast concrete pieces in a relatively small landscaped environment. Placing massive blocks requires bold commitment as well as physical effort, but such pieces express permanence with great clarity. Even a single specimen could be a strong addition to a garden, and a vote against more tentative actions.

Visit the Garden Conservatory’s Open Days website < www.gardenconservancy.org/open-days > for more information.

If you are ready to add plants to your garden, a good opportunity is the 5th Annual Native Plant Sale of the Watsonville Wetlands Watch. The sale will be 8:30–1:00 on Saturday, October 7th, at the organization’s resource center at the Pajaro Valley High School campus in Watsonville. The sale supports the group’s education and restoration programs in the Pajaro Valley. For info, visit www.watsonvillewetlandswatch.org/.

Grasses & Sedges in the Landscape

Gardening with flowering plants usually involves focuses on broad-leafed plants, which comprise the very large class of dicotyledons (“dicots”). In this column, we consider the monocotyledons (“monocots”), which include three families of narrow-leafed plants: grasses, sedges, and rushes. Dicots and monocots have several differences; most importantly, dicots have two embryonic leaves in each seed, while monocots have one.

Cultivation of these two classes of flowering plants has pretty much the same general requirements, plus the usual variations of specific plants. The narrow-leafed monocots, however, bring a distinctive form to the landscape and are also valued for such qualities as a gentle movement, drought tolerance, and low maintenance.

We might think of all garden-quality monocots as ornamental grasses, but grasses, sedges, and rushes each have unique shapes, which are described in a familiar rhyme: “Sedges have edges/Rushes are round/Grasses are hollow/What have you found?”

Gardeners can use ornamental grasses in several ways in the landscape. An excellent resource about many specific kinds of grasse and their uses is the exceptional book, The American Meadow Garden: Creating a Natural Alternative to the Traditional Lawn (Timber Press, 2009). Grass expert John Greenlee wrote this book, and garden photographer Saxon Holt provided excellent images. Their collaboration builds on their previous impressive works: Greenlee’s The Encyclopedia of Ornamental Grasses (with photography by Derek Fell) (1992) and Holt’s contributions to Nancy J. Ondra’s Grasses: Versatile Partners for Uncommon Garden Design (2002).

The sub-title of The American Meadow Garden emphasizes lawn grasses, but the book actually explores a variety of landscape uses of grasses: groundcovers, fillers, backgrounds, accents and natural lawns. Several grass varieties can be used in more than one of these ways.

Even a cursory scan of this book reveals an impressive range of garden-worthy grasses and their distinctive appearances. The garden designer is well advised to begin with a particular landscaping goal and then to look for grasses for optional approaches to meeting the goal.

My own current project, the development of a fairly large bed of Mediterranean basin plants, includes an interest in moving several existing sedge plants from another part of the garden. The plant is a European native, Grey Sedge (Carex divulsa). Interestingly, this plant had been — and might still be — sold as a California native plant called Berkeley Sedge or Foothill Sedge (C. tumulicola). It was correctly identified as C. divulsa in 2005.

Photo of Grey Sedge

Grey Sedge (Carex divulsa), often sold by the incorrect name, ‘Berkeley Sedge”

By any name, Greenlee calls this plant “by far one of the most versatile and manageable of all the groundcover sedges.” It grows twelve-to-eighteen inches high, and up to thirty-six inches wide, and is evergreen in the Monterey Bay area. It tolerates clay or sand and dry or moist conditions, and competes well with tree roots. It grows well in sun but prefers light shade. It’s true workhorse in the garden, and by most accounts attractive either as a single tussock or in larger areas.

This plant naturalizes easily to the point that some plant people consider it to be invasive. Unwanted seedlings can be removed easily enough, but gardeners should be aware of this plant’s ability to spread.

Grey Sedge will work well in the lightly shaded portion of my Mediterranean basin bed. I will plant divisions of the existing clumps about eighteen inches apart, and expect them to spread to form an interesting smallish meadow.

My specimens of Grey Sedge had been imposters in my California native bed, so their removal from that bed creates an opportunity to replace them with California native grasses. There are good options for accents and ground covers, to be explored in another column.

Becoming a Model of Irrigation Efficiency

As the summer draws to a conclusion, gardeners should consider landscape installations in anticipation of the rainy season’s onset. Right now is the best time to plan new plants. The coming rains will keep them irrigated as they develop roots and prepare to bud out in the spring. The rainy season usually begins in mid-October, so we now have time to decide on new plants, find them in a garden center or online nursery, and acquire them.

Because half of California’s urban water use is for landscape irrigation, all gardeners should be conscious of their landscape’s water need and informed about the preferred ways to meet those needs. Last winter’s rains were pretty good and supported the growth of very satisfying gardens, but the long-term potential remains for water shortages.

For these reasons, this is also the right time to update your plans for water use efficiency.

California’s Model Water Efficient Landscape Ordinance (MWELO) “promote(s) the values and benefits of landscaping practices that integrate and go beyond the conservation and efficient use of water” and “establish(es) a structure for planning, designing, installing, maintaining and managing water efficient landscape in new construction and rehabilitated projects…”

This ordinance applies to new landscapes of 500 square feet or more and rehabilitated landscapes of 2,500 square feet or more when either project requires a permit.

Such large-scale projects require a detailed Landscape Documentation Package that must be signed by the responsible parties and an auditor. For detailed information, browse to the website of the California Department of Water Resources and search for “MWELO.”

Most landscape renovation projects are not extensive enough to have to meet the comprehensive requirements of this ordinance, but its thorough approach is worth informal consideration on a voluntary basis.

The key component of the Package is the appended Water Efficient Landscape Worksheet, which is used to estimate evapotranspiration, i.e., the water evaporated from adjacent soil and other surfaces, and transpired by plants, and to calculate the evapotranspiration adjustment factor (ETAF). The Worksheet guides the calculation of the ETAF which considers the major influences on the amount of water required by the landscape: plant factors and irrigation efficiency.

For residential areas, the ETAF should not exceed .55. This figure is then used to determine the Maximum Applied Water Allowance (MAWA) and the Estimated Total Water Use, which must be below the MAWA.

This explanation uses the minimum number of acronyms!

The simpler approach to efficient water use in the landscape involves two concepts. First, choose plants with lower water needs. The obvious choices are California native plants and succulent plants. Second, use drip irrigation to control the amount and location of water usage. The state provides a useful planning resource, “A Guide to Estimating Irrigation Water Needs of Landscape Plantings in California.” It’s available without cost from the California Department of Water Resources website. Search for “WUCOLS.” That one more acronym stands for “Water Use Classifications of Landscape Species.” The Guide document includes the water use needs of many garden plants, listed by both botanical and common names.

Planning for efficient irrigation helps to conserve the state’s limited water resources, and, for the gardener, minimizes the cost of water usage and supports effective plant growth.

This planning pays off!

Discovering Gladioli

My garden includes several gladioli. I do not recall planting even one of these plants, but there they are, almost always in the wrong places. They have popped up, for example, in the middle of the rose bed, and on the edge of the entry path to my front door.

One definition of weeds is “plants that grow where they are not wanted,” but these plants have attractive blossoms. In fact, the sword lily—as it is sometimes called—is among the most desirable plants for cut flowers. The blossoms are available in many different colors.

Now that their blossoms have faded and the stalks are drying out, it’s the right time to corral their spread and get them growing in better places. This calls for some research.

The genus Gladiolus is a member of the iris family (Iridaceae), including about 300 species, the large majority of which are natives of South Africa. The species range in height from 1.5 feet (G. tristis) to 3 feet (G. callianthus, the Abyssinian Sword Lily) to 6 feet (the common grandiflora hybrids).

Gladiolus byzanthus By Meneerke bloem

Gladiolus byzanthus
By Meneerke bloem

The 5.5 feet plants that have appeared are probably garden hybrids and are best placed in the middle or back of the bed.

Once the plant’s blossoms have turned brown, the stems should be cut below the lowest flower to discourage the plant from setting unwanted seeds. In the Monterey Bay area’s moderate climate the corms can be left in place, or dug for planting in a different location. My garden is organized geographically, so I will replant the corms in the South African bed.

Once dug, the corms can be grouped in three categories: old, large corms are viable but lack vigor; younger corms at least .75 inches in diameter will produce blossoms in the spring; and cormlets about the size of peas can be planted to produce blossoms after a year of development.

Corms may be stored in a cool, dry, dark and well-ventilated place until replanting in the following year from January to March. After planting they will bloom reliably in 80–to–100 days, depending on the variety. This invites succession planting about 1 or 2 weeks apart to yield a series of blooms for cutting or enjoying in the garden.

The corms should be planted where they will get rich soil, full sun, and good drainage. They should be planted about 4 inches deep and about 6 inches apart. Apply an organic, water-soluble fertilizer when the plants are 10 inches tall, and again when the flower spikes begin to show color.

As the plants grow, they might require staking, either with individual stakes or a grid made of stakes and string (but almost none one of the several volunteers in my garden has flopped).

As sometimes happens, plants that introduce themselves unexpectedly in the garden can be appreciated and welcome. So far, I am glad to discover gladioli and looking ahead to a fine display in the spring and summer of next year. I might even become interested in buying corms of different species and different colors.

For information about gladiolus varieties and cultivation of these plants, visit the website of the North American Gladiolus Council.

Designing with Succulents

An avid gardener I talked with recently mentioned that he and his wife are not at all interested in succulents. They have none in their garden and do not intend to add any.

I wasn’t advocating succulent plants at that time, but I find their preference to be puzzling. In fact all plants store moisture to some degree; those we call “succulents” just have more effective ways of managing during dry periods.

Given this perspective, we might consider the reasons why many gardeners find succulent plants to be appealing and others do not.

Some who don’t like these plants might think all succulents are cacti with sharp points, and don’t want to be harmed. We must respond with the old line that all cacti are succulents, but all succulents are not cacti. Also, a few cacti do not have sharp points, and a few succulents that are not cacti also have sharp points. With simple precautions the gardener can avoid being poked, and with study can appreciate Nature’s strategy for some plants to defend themselves from hungry predators. (Cactus spines are really modified leaves designed to minimize moisture loss.)

Other gardeners who don’t like succulent plants might just be unfamiliar with their great variety of forms, structures, colors, landscape value, and unique qualities. For these gardeners, an excellent introduction to succulent plants is Debra Lee Baldwin’s new book, Designing with Succulents (Timber Press, 2017). This book, due for release later this month, is the completely revised second edition of Baldwin’s 2007 book of the same title.

Screen Shot 2017-08-09 at 12.28.50 PM

Baldwin has organized her ideas about succulent plants in six sections: essential garden design ideas; specialty gardens; cultivation advice; descriptions of selected plants; categorized lists of plants; and drought-tolerant companion plants.

Each section includes the author’s solid information based on her own gardening knowledge and inputs from other experts, and excellent images from her own work and other photographers. Baldwin brings a strong background of garden writing and photography to this task, as well as extensive experience in gardening. She is also a popular speaker and a producer of many short YouTube video recordings on succulent gardening.

Other books provide an encyclopedic resource or a botanical analysis of succulent plants, but Designing with Succulents, as its title indicates, focuses on design ideas for landscape vignettes, plant combinations, and containers. The book shows and describes exciting examples of designs from public and private gardens in southern California, and several other parts of the United States.

Among many other ideas, Designing with Succulents demonstrates the aesthetic value of larger plants in the landscape. Familiar good advice for adding plants to the garden includes being aware of the plant’s mature size. Buying only small plants minimizes expense, but filling the garden with plants that will never grow into larger size leaves the landscape with little drama or architectural interest.

Gardeners new to these plants will find both useful information and inspiration in this book. Experienced growers of succulents also will discover motivation to explore possibilities for refining their gardens and containers, and enjoying gardening with succulents.

Propagating Softwood Cuttings

I like to know the names of the plants in my garden, partly because I can Google them for information about cultivation and routine care. I also want to know their geographic origin because I have organized my garden in Mediterranean climate zones, and want the plants to be in the right zone.

That’s a bit wonky, I know, but that’s how my garden is organized.

Despite that need for plant names, I lost track of the name of a plant in the Australian area of my garden. Here is the plant:

Teucrium betonicum - close up

Teucrium betonicum

By chance, I came upon the plant’s name while searching the Internet for examples of landscape designs for Mediterranean climate gardens. It is a Madeira Germander (Teucrium betonicum), which is from the Madeira Islands, which are in the Atlantic Ocean, near the Canary Islands. That area is within my informal definition of the Mediterranean climate zone.

Other germanders are native to other parts of the Mediterranean area. A popular plant for Mediterranean climate landscapes is the Bush Germander (Teucrium fruticans). My germander is considered “relatively rare,” which I find appealing for some reason.

This plant grows vigorously, rising to just over six feet with evergreen foliage and showy spikes of rose-violet flowers. According to my landscaping plan, however, it is in the wrong place. This plant grows vigorously, rising to just over six feet with evergreen foliage and showy spikes of rose-violet flowers. According to my landscaping plan, however, it is in the wrong place.

I’d like to move the plant to the Mediterranean area of my garden. I might give that a try during the winter months after it is out of bloom and into dormancy. It might move easily and survive nicely, or the process might kill it.

I might look for a replacement plant, but I haven’t seen this “relatively rare” plant in local garden centers and searches of mail order sources were unsuccessful.

An alternative approach is to propagate the plant from tip cuttings. This strategy requires time for the new plants to grow to maturity, but it is easy and inexpensive. I could use three specimens in my Mediterranean garden, and growing three new plants would require only slightly more effort than growing one.

As it happens, late spring/early summer the right time of the year to propagate shrubs. The most difficult part of the process is to take cuttings at the right maturity, called softwood. Greenwood cuttings are too young, and woody cuttings are too mature. Softwood snaps when bent, while green wood bends without snapping and wood does not bend.

Take a softwood cutting that has two or three leaves, and neither bud nor blossom. Cut an inch or so below the bottom leaf, then remove the bottom leaf. This leaves the leaf node from which roots will develop. Treat the leaf node with root hormone (available at garden centers), and insert the cutting into moist potting soil. Press the soil around the cutting to eliminate air pockets, and place the cutting in a warm spot with indirect light. Keep it moist (not wet) for about a month, and test for root growth by tugging gently on the cutting. Once roots have formed, maintain the plant as it grows to begin enough for transplanting in the garden.

This outline of softwood propagation shows that the process is not difficult; more detailed descriptions of the process are available in books or on the Internet.

If you haven’t tried propagating a favored shrub from your garden or another’s garden, right now is a good opportunity to try this “real” gardening activity. Propagation is most satisfying when you could use several clones of a plant to develop your garden or to give to friends.