In Praise of Japanese Maples

Trees add to the garden landscape in various ways. Often, very large trees will dominate the scene, and bring stability and grandeur to the scene, and shade a large area. In time, they can be desirable components to the garden and add value to the property.

By contrast, small trees contribute to the landscape in different ways, notably as specimen plants that attract the eye with their specific features, e.g., blossoms.

Unless you have a relatively large garden, a large trees can be overwhelming, and a small tree can be a delight.

There are many choices of small trees, which might be called “patio trees,” even though they have roles to play in all parts of the landscape.

Today, let’s review the Japanese Maple, which many gardeners and landscapers regard as the most popular of the small trees.

The true Japanese Maple is Acer palmatum. Other Acer species, including A. japonicum and A. shirasawanum, are also called Japanese Maples, and have attractive characteristics. Still. A. palmatum has been the focus of hybridizers in Japan for centuries, and has been favored by western horticulturists since its introduction to England in 1920. The species now includes well over1,000 cultivars.

The extraordinary range of sizes, forms, leaf shapes and colors of A. palmatum reflect the long history of its development and stimulate the interest of gardeners and landscapers. Those who have the pleasure of gardening in large spaces can be tempted to collect large numbers of A. palmatum cultivars.

For most gardeners, however, even one Japanese Maple can be rewarding. Even very small gardens, including balcony gardens, can be enhanced with one of these trees, which range in mature height from the dwarf varieties (three-to-six feet) up to twenty-five feet. They grow well in containers, and will ”self-stunt” when their roots are confined. This characteristic makes Japanese Maples popular with bonsai artists.

acer-palmatum-unknown-cultivarThe accompanying picture shows one of my Japanese Maples as it begins to show its fall color, which is the typical seasonal variation of these trees. It has grown to about eight feet, with distinctive red twigs, but sadly I have lost track of the cultivar name.

Many gardeners will locate a Japanese Maple as a garden feature or focal point, where the color or leaf form of the selected variety can be appreciated. With this in mind, once you have become interested in adding a Japanese Maple to your landscapes, consider where it would be best located. This decision should involve envisioning the tree in several spots in the garden, and from different perspectives. This process draws upon the most creative work of gardening. Think of your new tree as a living sculpture.

Also, keep in mind that Japanese Maples prefer part sun or indirect light, good drainage and consistent watering. They like a slightly acidic soil and do not like cold winds or salt air. Plan to provide regular watering during the first year after planting.

A Japanese Maple or several of these small trees could enhance your landscape during future years. Right now is a good time to decide on the best location, explore the range of cultivars and choose a fine selection to install in your garden before the start of winter rains. Continue reading

Seasonal Succulents

Succulent plants, like all plants, have seasonal growth patterns. Plants in this category come from numerous genera, and have a wider variety of forms, textures, and colors, but they can be divided into just two principal growth patterns: Winter Dormant (“summer growers”) and Summer Dormant (“winter growers”) (see lists at the end of this page).

It would be comforting to find that Winter Dormant succulents are native to the Northern Hemisphere and Summer Dormant plants are from the Southern Hemisphere, but it’s not that simple. It could be that growth patterns sometimes reflect a genus’s adaptation to its adopted environment.

In any event, a succulent plant’s growth cycle affects its need for water and its bloom period. These plants require minimal watering during their dormant period and will produce blossoms during their growth period.

If you have a large and varied collection of succulents, a good practice is to cluster separately the Winter Dormant and Summer Dormant plants, to simplify watering.

Except for their blossom periods, many of which are delightful but rather brief, succulent plants are favored mostly for the shape, texture, and color of their foliage, which changes little through the seasons, except for size.

Most popular plant genera have very specific annual cycles. Shows and sales of roses, irises, dahlias, tulips, daffodils, and amaryllis, for example, are very seasonal events. Succulent plant shows and sales, however, could occur at any time of the year.

In contrast, California’s cactus & succulent societies hold their sales during the period from April through September. These sales offer the greatest variety and best prices, but gardeners can find at least the more common plants at their local garden center throughout the year.

For local gardeners, important dates for cactus & succulent sales include the spring and fall events organized by the Monterey Bay Area Cactus & Succulent Society. These occur each year in late April and late September or (this year) early October.

Another noteworthy occasion is the Succulent Extravaganza, presented with free admission by Succulent Gardens, a commercial entity. A highlight of this year’s event, on September 23 & 24, was Debra Lee Baldwin’s talk on “Bulletproof & Beautiful Succulents for your Garden.” Ms. Baldwin, called the Queen of Succulents, described a variety of attractive plants, emphasizing various forms of the genus Echeveria. I brought home an unusual and rare carunculated (warty) hybrid, Echeveria x Barbillion, which is shown by the accompanying photograph.


During our brief conversation, Debra Less Baldwin and I exchanged stories about “midnight acquisitions” of succulent plants from both public and private gardens. I’ll write on that topic in another column.

The next important opportunity for gardeners to build their succulent collections is the Fall Show & Sale of the Monterey Bay Area Cactus & Succulent Society. This event offers opportunities to talk with other gardeners who are enthusiastic about these plants and choose from an amazing array of small, inexpensive plants. There will also be a display of exceptional specimens, which you can vote on for a People’s Choice award, and a selection of unique containers that are right for artful presentation of succulent plants.

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Seasonal Events


At about this time each year, our thoughts drift to certain seasonal topics. For example, this is the time to plan a display of spring bulbs. I thought I should write about this activity (which can lead to adventuresome ideas), but I have already written before on this topic. To see earlier columns, browse to and search for “bulbs.”

Let us consider other aspects of seasonal gardening.

The annual Succulent Extravaganza is happening this weekend. This is a fine free event to learn about and become fascinated by succulent plants. If you are already collecting and landscaping with these interesting plants, the Extravaganza offers a selection of plants to add to your garden. For info, visit and click on ”Events.”

The next really big event for succulent gardeners is the Fall Show & Sale convened by the Monterey Bay Area Cactus & Succulent Society. This event will happen on October 1st & 2nd, in nearby San Juan Batista, California. Nineteen members of the Society will offer a vast array of small succulent plants, many larger plants and some unique pots for sale. The selection is great, the prices are very good, and members of the group will be available to answer specific questions and share their enthusiastic for gardening with succulents. The display of exceptional plants is a “must-see” event in its own right. For info, visit .

Dudleya brittonii - cu

Dudleya brittonii — a California native succulent plant

Toward the end of October, an event for gardeners is the annual apple tasting, organized by the California Rare Fruit Growers, Monterey Bay Chapter. This will be included in the Wilder Ranch Heritage Harvest Festival, which is on October 15th. It will be a unique opportunity to learn which apple tree you want to plant in your garden. The Festival also includes other interesting activities. Info:

The UCSC Arboretum’s annual Fall Plant Sale will be on Saturday, October 15th. It will be open to members of the Friends of the Arboretum from 10-12, and to the public from 12-4. Just before the sale, you could join the Friends. There are year-round benefits to belonging to the Friends, in addition to gaining early access to the Sale, which offers a great selection of plants from California, Australia, and South Africa. The California Native Plant Society will have a concurrent sale, at the same location: the Arboretum’s Eucalyptus Grove, which is accessible from High Street, near the intersection of Western Drive. Info: http://

The Friends of the University of California, Santa Cruz Arboretum held its annual meeting —called the “AR-B-Q” — on Sunday, September 18th, in the Australian Garden. This was a fine, convivial event, as always, with many volunteers enjoying the company and the warm weather. The meeting included thanks to retiring board members (including this writer), the election of board members, and the announcement of officers for the coming year.

Several readers of this column have expressed interest in our recent column about the book, The Invention of Nature, about the extraordinary Alexander von Humboldt 1769-1859. On October 19th, the Garden Conservancy will sponsor a visit of the book’s author, Andrea Wulf, at the UC Botanical Garden at Berkeley to discuss the influence of Humboldt’s vision, and how he helped shape our understanding of nature today. Wulf ‘s very readable book reflects her thorough research and inspires interest in her other highly regarded books about gardeners:

This Other Eden Seven Great Gardens and Three Hundred Years of English History

The Brother Gardeners. Botany, Empire and the Birth of an Obsession

The Founding Gardeners. The Revolutionary Generation and the Shaping of the American Nation

For info on WUlf’s talk at UC Bekjeley, visit the Garden Conservancy website:

The gardening world is very lively, as always. Enjoy your garden!


Tom Karwin is past president of the Friends of the UC Santa Cruz Arboretum, president of the Monterey Bay Area Cactus & Succulent Society, and a Lifetime UC Master Gardener (Certified 1999–2009). Visit for links to information on this subject, and send comments or questions to

Labeling GE Foods: New Issues

The federal requirement to label foods with genetically engineered ingredients is generating turmoil in the marketplace.

To review, a very large majority of U.S. consumers demanded labeling of GE foods, and the food industry spent a reported $400 million to defeat related legislation. The debate, which continued for over five years, resulted in late July of 2016 in the adoption of “compromise” legislation that strongly favored the food industry’s position.

The central issue in the debate has been a policy of 1992 under which the U.S. Food & Drug Administration (FDA) concluded that the health and nutrient values of genetically engineered foods do not differ from “conventional” foods and therefore do not warrant labeling.

Labeling advocates have insisted that GE foods have not been studied sufficiently by independent researchers, and federal policy ignores the environmental and economic impacts of such foods. Senator Dianne Feinstein (D-CA) supported labeling by pointing to consumers’ strong interest in knowing when foods contain GE ingredients.

Consumer groups are still a bit stunned by the adoption of what has been called “the weakest labeling law imaginable.” They continue the struggle, but have abandoned the political arena and are moving future battles to the marketplace.

The simplest strategy is buy only foods labeled as organic, under long-standing federal standards. Organic foods, by definition, do not contain GE ingredients.

The flipside of this strategy involves boycotting foods that are not labeled “organic” or “non-GE.”

A related strategy includes rejecting foods labeled as “natural.” Some consumers regard “natural” and “organic” as equivalent but current FDA practice states that “natural” foods do not include artificial ingredients. The FDA is being pressured to define “natural” in a way that includes foods with GE ingredients. We’ll see how that goes!

Another strategy is take legal action against companies that label foods as “organic” when they in fact contain GE ingredients. To date, such initiatives appear to be effective.

One group has mounted a campaign to label selected conventional foods with the “Non-GMO Project Verified Butterfly.” Such labels are becoming more used, reportedly.

One thoughtful observer, food writer Mark Bittman, has suggested that the GE labeling “cloud” has a silver lining, because the new labeling law opens the door to a new era of transparency about food products. He notes that the new law, however flawed, calls for labeling a food’s production process in addition to labeling its health and nutrient values.

Bittman lists the new categories of information that consumers should be told about a food product’s ingredients: Where are they from? Were they dosed with pesticides or other synthetic chemicals? How much water was used to grow them? Did farm workers receive fair pay and treatment? Were farming practices friendly to the environment? For food products from animals: Were the animals treated with antibiotics? Were the animals treated humanely?

Such labeling requirements might be required on a state-by-state basis, which is still permissible under federal law. State-level responses to consumer interests in such areas could force the adoption of overdue national standards regarding food production processes. GE labeling might be only the beginning of a much-needed “transparency revolution.”

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The Invention of Nature

California’s Board of Education has included five environmental principles for the curriculum:

  • People depend on natural systems.
  • People influence natural systems.
  • Natural systems change in ways that people benefit from and can influence.
  • There are no permanent or impermeable boundaries that prevent matter from flowing between systems.
  • Decisions affecting resources and natural systems are complex and involve many factors.

These very basic ideas certainly are important in learning about the environment.

These principles are an updated version of ideas that were expressed in the early 1800s by Alexander von Humboldt (1969–1859), who presented his views of how the forces of nature interact with one another and about the unity of nature.

At the time, Humboldt’s ideas were the leading edge of leading scientists’ understanding of natural systems. He developed these ideas by traveling extensively through South America and Central America, closely observing nature, and, significantly, learning from the wise practices of native populations.

Humboldt was one of the great polymaths of history. He was the earliest geobotanist, studying the geographic distribution of plants (also called phytogeography), but also made important contributions to meteorology, and geology. His greatest contributions are in the area called terrestrial physics, which deals with the dynamic interconnections that comprise natural systems.

A new book by Andrea Wulf describes Humboldt’s momentous journey through life in impressive and readable detail: The Invention of Nature: Alexander von Humboldt’s New World (Knopf, 2016). The book is organized chronologically, in five parts.

Humboldt shared his extensive knowledge and advanced ideas through extensive publications, correspondence, and public lectures. His major work was Cosmos. Sketch for a Physical Description of the Universe. This five-volume work, was widely read and highly regarded, and added to his reputation as the greatest scientists of his era.

Humboldt conversed with many prominent people of his day and directly or indirectly influenced a long list of scientists, authors, and political leaders, too many to list here.

Today, Humboldt might not be known as well as some other early scientist. Author Andrea Wulf has commented that the truth of Humboldt’s views has become so widely accepted that the man himself has become less visible. Still, many admirers have honored him by attaching his name attached to more places and things than anyone else. These include a northern California county. An impressive list of these recognitions is available in Wikipedia’s entry for Alexander von Humboldt. (See also Wikipedia’s entry, “Humboldtian Science.”)

Andrea Wulf, who has also written about other historically important botanists, has provided a masterful, readable, and valuable account of the “formidable genius” Alexander von Humboldt. The New York Times named The Invention of Nature as one of the best books of 2015 and several additional reviewers recognized its quality, This book presents the fascinating story of a man who explained the natural context in which gardening is done.

Working with Contractors

A friend recently showed me an area that she wanted to landscape, and asked about a designer. I was able to recommend another friend (an accomplished designer) but the project motivated me to review the “design & install” category of landscaping projects.

The basics of landscape design often are described by a few broad guidelines:

First, consider how you will use the landscaped area. Too many spaces are created for certain purposes and then little used because the homeowner doesn’t really enjoy outdoor entertaining, the kids have grown and flown, the design requires too much maintenance, etc.

Then, learn all you can about the area to be developed. Make at least a rough scale drawing of the area. Mark important plants or other features that are to be retained. Indicate significant microclimates, e.g., deep shade, windy areas, water-retaining swales. Diagram that seasonal path of the sun. Have the soil tested.

Bring in a designer, unless you are confident in your own ideas and plant selections. These days, it’s good to find someone who understands and practices soil regeneration, integrated pest management, and organic practices in general. The Green Gardener program lists landscapers with up-to-date training. Contractors with long years of experience might be skilled in—and committed to—outdated methods.

Begin the install process with any required grading and the hardscape elements, e.g., paths, retaining walls, ponds, garden structures.

Missy Henriksen, of the National Association of Landscape Professionals, recently recommended ways to have an effective partnership between client and contractor. (If you visit the NALP website, click on the “Consumers” tab for ideas for homeowners.)

Here are Missy Henriksen’s tips, with my running commentary.

Communicate your long-term vision for your lawn. Well, lawns are on their way out, because to look really good they need a lot of mowing and edging, and synthetic chemicals. Otherwise, the advice is to be clear about longer-term visions, so that the contractor can provide a phased plan.

Understand the importance of working with native flowers, shrubs, and trees. Plants that are native to your specific area will thrive in your garden, while exotic imports will require extraordinary efforts to keep them alive and growing, and might still struggle.

Consider what time investment you want to make in your landscape after the installation is done. The late gardener and garden writer, Christopher Lloyd, favored high-maintenance gardening, which could entail changing plants frequently to provide year-round color. That practice has made his garden, Great Dixter, famous, but it’s not every gardener’s priority.

Allow adequate time for your landscape project. Certainly, the client should accept the reality that everything takes longer than expected, but it’s also reasonable to expect your contractor to make steady progress on your project, and not compromise that progress to work on someone else’s priority.

Know your budget. Address financial constraints by a phased approach to your longer-term objectives. A little self-discipline can be frustrating but better eventually than wishful thinking. On the other hand, the best results can result from thinking big.

Communicate any special community rules. A good landscaper should know, or found out about, restrictions by local government, or a homeowner’s association. Your standard should be “No surprises!”

Ask any lingering questions. A good practice is to require a written contract that covers all significant issues. For larger landscaping projects, refer to “A Consumer Guide to Home Improvement Contracts” and “Choosing the Right Landscaper,” both publications of the California’s Contractors State License Board. Accept the contracted work only after satisfaction of applicable standards of the landscaping industry, rather than approval by the local government or a homeowner’s association.

A successful landscaping project can give the garden owner long-term satisfaction and yield a substantial boost to the value of the property.

Survey of Garden Customers

Your local garden center has a continuing interest in what its customers seek and will seek in the future. That information has much to do with the success of the business.

One important source of trends among gardening customers is the National Gardening Survey, a private company that conducts annual surveys of consumers of garden-related products. The NGS has recently released its 2015 survey.

The full survey is quite pricey, but in today’s column we summarize the available highlights with an emphasis on the gardening customer’s perspective.

The bottom line of the survey findings has been summed up as “a bold, exciting future for garden retail!!” That’s good news for your local garden center because it reflects growing interest among gardeners.

The NGS estimates that 75% of all U.S. households are undertaking some level of gardening. That works out to 90 million households, an increase of six million households over 2014.

When analyzed by age, 5 million of the additional gardening households had participants in the 18–to–34-year-old range, the group often called the “Millennials.” Meanwhile, the number of households with participants in the 55+-year-old range reportedly remained steady. (This leaves an increase of 1 million households presumably with ages 35–to–54.)

So, gardening customers got a little younger, on average.

The average annual expenditure on gardening rose from $317 to $401 per household, a stunning 26% increase year–to–year, and about 10% over the average of the previous five years. This combination of more customers and more spending makes the lawn and garden industry optimistic.

The overall receipts of this industry total $36 billion, which is notably about three times the Hollywood box office receipts. Still, household spending for gardening products and services, when adjusted for inflation, remains well below the peak reached in 2003.

The NGS’s findings don’t reveal why the rate of spending for garden items lags below the historical peaks, but one plausible interpretation is that gardeners are getting smarter by using online information.

The NGS has concluded that garden customers are discovering the information they want through online research and then seeking validation at their local garden centers. This pattern contrasts with past practices in which customers asked garden center staff for basic information.

The NGS recommends that garden center should focus more as project success centers, rather than hand-holding discovery centers.

As your local garden center modifies its services in this way, you must find answers to your gardening questions on your own, using online resources, books and magazines, and fellow gardeners. Local garden societies can be important sources of basic gardening information.

This column often refers to online sources of gardening information, and will continue to include helpful web addresses. The success of any search for information begins with a thoughtful formulation of the question. Books have been written on strategies for asking the right question, which is central to critical thinking, but acquiring basic factual information about gardening need not be complicated. Many questions for such information can begin with “how” or “what,“ e.g., “how do I plant a tomato?” or “what is a good way to plant a tomato?”

When seeking such information online, many search engines can respond to natural language queries, but they are really oriented to keywords. You will get pretty much the same response by entering “tomato plant.”

The staff at your local garden center surely will continue to respond to your factual questions, but the Internet will be more readily available and will offer a deeper trove of information.

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Architectural Plants in the Garden

A current project in my garden involves relocating a specimen plant to a more prominent site, to take advantage of its current and anticipated appearance.

The plant is Giant Cabuya, a member of the Agave family (Agavaceae). In English, Cabuya means Agave, but it might also mean fibre. The plant’s botanical name is Furcraea foetida ‘Mediopicta’.

Native to the Caribbean area and northern South America, this succulent plant is widely grown as its variegated leaves can create a five-foot wide display and a spectacular presence in the landscape.

Brazilian Plant

Furcraea foetida ‘Mediopicta’

It will produce a 25 feet tall flower stalk on an apparently unpredictable basis. The inflorescence is unremarkable in appearance but reportedly strongly fragrant. The specific epithet, foetida, means “stinking.”

Once the presents its great flower stalk it will die. Like other monocarpic plants, e.g., the Century Plant (Agave Americana), it will propagate itself by generating adventitious shoots, or “pups.”

The plant’s strongest points are its colorful leaves, which first attracted my eye. Because it was labeled as native to Brazil, I brought it into my garden as a plant familiar to a Brazilian graduate student who was staying in my home. (He recognized it, but was more interested in his studies of microbiology.)

I put the Giant Cabuya in a large terra cotta pot, where it grew well for more than a year, and spread about three feet wide. I learned that it would reach its maximal spread only when grown in the ground.

I had recently renovated an overgrown cluster of Peruvian Lilies, and reshaped the planting bed into a roughly circular form. The new bed, currently without plants, needed redesigning, with a focal point. A dramatic sculpture would be appropriate but not in the budget, so a large plant with architectural character could serve as the purpose of a focal point.

This was to be the new home for the Giant Cabuya.

The bed was large enough for the plant to grow to five feet wide, and eventually to throw up its malodorous flower stalk.

A short list of plants can be useful as focal points in the landscape. Large succulent plants, particularly those in the Agave family, have good qualities for this purpose. This is a matter of individual preference of course, but long, sturdy leaves can form a roughly symmetrical display that is readily perceived as sculptural.

For an interesting overview of architectural agaves, visit the website of succulent expert Debra Lee Baldwin, navigate to Videos and look for “Six Great Agaves for Your Garden.” In this video recording, renowned agave hybridizer Kelly Griffin casually demonstrates agaves that would work well as focal points in the garden.

In addition to the larger agaves, several other plants have architectural value. If your garden could benefit from an eye-catching, prominently placed plant, look for candidates when you visit your local garden center. A dramatic feature could add interest to your landscape.

Pruning Tomato Vines

A great many tomatoes are available to home gardeners, either as seeds or seedlings. We are already well into the growing season, so if you enjoy growing tomatoes you are probably already past the stages of selecting a variety or planting seeds or seedlings.

If you are already skilled at pruning your tomato plants, and doing the job in a timely manner, you will not need to read this column.

For the rest of us, let us review the pruning process, with an emphasis on corralling a runaway tomato vine.

The first bit of knowledge about growing tomatoes is that the multitude of cultivars includes just two types: determinate and indeterminate. The determinate plants develop a number of stems, leaves, and flowers, as predetermined by their genetics, and then stop growing. The fruits (actually berries according to the experts) all ripen at the same time, relatively early in the growing season. Pruning of these plants only reduces the harvest.

The indeterminate plants continue to grow and produce stems, leaves, and fruits throughout the season. These are the plants that need controlling.

Expert grower Frank Ferrandino, writing in Kitchen Gardener Magazine, warned, “Left to its own devices, a vigorous indeterminate tomato plant can easily cover a 4- by 4-foot area with as many as ten stems, each 3 to5 feet long. By season’s end, it will be an unsightly, impenetrable, disease-wracked tangle.”

I am growing three tomato plants this year, all of which are the variety, Super Sweet 100, a popular bite-size tomato. I grew one of these plants last year, watched it produce a bounty of very tasty little tomatoes, and develop into the tangle that Frank F. warned about.

Long after I had cleared the bed, a new spring arrived and several seedlings of Super Sweet 100 appeared. I replanted three of the best, determined to control the plant better.

The goals of pruning a tomato plant are to promote larger fruits (not really an issue for cherry tomatoes), keep the plants tidy, and keep the plants off the ground to minimize the potential for disease. The Super Sweet 100 is a disease-resistant variety, but keeping the plant tidy and off the ground still seems worth the effort.

The basic pruning technique is to remove side shoots, called suckers, that grow in the crotch (axil) between the main stem and the side stems. These suckers can produce fruits, but they tend to develop later than the primary fruit-bearing stems and reduce the plant’s vigor.

Tomato plants grow rather quickly, so the removal of suckers is a weekly task. When the suckers are very young, they can be snapped off without the use of tools.

Despite my nest intentions, my plants were soon well on their way to the predicted tangle. This condition inspired an experiment, which took the form of brutally cutting back branches that were sprawling in all directions and in several instances producing little or no fruit.

Super Sweet 100s (green)

More systematic training surely would have been better, but this approach was really the only option at the time. I expect and hope the plants will shrug off my abandonment of best practices and produce another bountiful harvest of sweet, small fruits.

Those fruits are mostly green, still, but have plenty of time to ripen. I’ll try again next year to prune by the book.


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Another Garden Thug—Castorbean

I have observed recently that certain plants bring a mix of good and bad traits to the garden. In some cases, a plant’s positive characteristics can offset the negative ones. As a result, the gardener might want to include the plant in this landscape and accept the reality that it will require “special handling.”

One such plant is the castorbean (Ricinus communis), also known as the castor oil plant. This is a member of the spurge family (Euphorbiaceae), native to the southeastern Mediterranean Basin, Eastern Africa, and India. It grows as a large shrub that can attain a height exceeding thirty feet. The popular garden varieties, however, grow to ten feet or less.

The plant has several positive qualities, foremost being the striking appearance of its leaves, which are palm-shaped (palmate) and dark reddish-purple in color, becoming green with age. The shrub grows fairly quickly, and the gardener can control its shape with regular pruning. Also, being native to a Mediterranean climate, the castorbean, once established, is drought tolerant in the Monterey Bay area.

Castorbean leaves & seeds

Castorbean seeds, leaves and flowers

Another positive quality is the plant’s usefulness for medicinal, insecticidal, and industrial purposes. There are several medicinal uses, including as a laxative. The greatest commercial value of the beans (actually seeds) is for motor lubrication. These applications do not, however, contribute to its value in the garden.

The negative qualities must be acknowledged. First, the raw seeds are extremely toxic when chewed. They have been described as the most poisonous in the world. The seeds can be attractive and tasty-looking, but as few as four-to-eight seeds can be fatal to an adult. If you have this plant in your garden, you should ensure that neither children nor pets have opportunities to sample the seeds.

The plant is also strongly allergenic. Its pollen can trigger asthmatic attacks, and its sap can cause skin rashes.

Another negative quality is the castorbean’s tendency to propagate itself by dropping seeds. My plant has generated several crops of seedlings within a circle about thirty feet in diameter, centered on the mother plant. How the seeds plant themselves well beyond the plant’s drip line remains a mystery. The seedlings grow quickly up to three feet in height, but are easily uprooted. They do not transplant well, so I have not potted them for other gardeners. They might have inspired mixed reactions, especially by gardeners with children or pets.

Despite its toxicity and allergenic potential, the castorbean is grown for its ornamental value throughout the world in compatible climates. This reality demonstrates the appreciation of avid gardeners for plants that bring unique contributions to the landscape.

For at least some gardeners, the castorbean’s reddish-purple leaves are more important than the effort involved in protecting against the plant’s poisons and eradicating its unwanted progeny.

Each gardener must make such decisions for his or her own garden.