Landscaping Priorities

This year’s Fall Equinox lands on September 22, marking the unofficial start of the planting season.

Installing new plants in your garden during the fall provides them time to establish roots and prepare for leafing out and blooming in the spring. Ideally, we would have our historic pattern of winter rains during this time, so that the plants will have ample moisture to work with.

An additional benefit of this planting schedule might include end-of-season plant clearance sales at your favored garden center or nursery. You can feel like a savvy garden shopper when you acquire plants at good prices in the fall, and resist the temptation to stock up in the spring, when small plants have been forced into seductive blooms with nitrogen fertilizers.

The planting season is still a couple weeks away, so right now is a good time for planning to select and install plants in your garden. Having a plan when you open a mail order catalog or walk into a garden center will prepare you to focus your targets and avoid becoming overwhelmed by the array of possibilities.

Strategies for garden planning in the Monterey Bay area include emphasizing drought-tolerant plants, or California native plants, or a particular theme of your own choosing. Earlier versions of this column have addressed such strategies.

Today’s column describes additional strategies suggested by Rochelle Greayer, author of Cultivating Garden Style (Timber Press, 2014). In her online newsletter, Pith + Vigor, Greayer recently identified three mistakes that gardeners make when designing with plants:

  • Too many different plants
  • Not enough plants
  • Planting just the plans you know.

Let’s consider positive strategies in these three areas.

First, develop your landscape around a just nine to twelve different plants. Selecting plants in this short list for specific roles will bring order and cohesion to the landscape, and avoid the chaos that too often results from impulsive additions of individual plants.

Second, once you have selected your short list of plants, install lots of them. This strategy is related to adding plants in clusters of three, five, or any other odd-numbered quantity, to present them in a natural and pleasing manner. As you reach larger numbers, install the plants in swathes or bands to provide a landscaping effect. Greayer says, “Repetition gives a scheme flow and rhythm. Repetition is a savvy designer’s best trick.” For example, I recently planted two parallel arcs of blue and yellow irises as a color statement for next spring. Over the next few seasons, these plants will increase to provide increasingly dramatic displays.

A swath of Dalmation Iris (Iris pallida ‘Variegata’) backed up with Lavender plants
A bed of hardy geraniums (Geranium × cantabrigiense ‘Biokovo’ ) with a garden art pheasant

Related to the idea of repetition planting is the installation of plants with close spacing. While you might be tempted to spread plants out to cover space in the garden, having open areas between plants reduces their visual impact and invites the growth of weeds. Close spacing reflects the natural tendency of plants to propagate and develop into colonies. It also functions as “green mulch,” denying weeds the sunlight they need to develop.

Third, explore the wonderful world of plants to find good choices for your short list of selections for the landscape. It’s always important to select plants that are suitable for the climate, soil and exposure of the locations for which you are planning, but there are always many interesting selections that are both suitable for your garden and new to your experience. Relying on common and familiar plants will doom your landscape to being (gasp!) ordinary. Discover interesting plants that will bring excitement to your garden, and invest time in learning how to cultivate them successfully.

In review, there are three strategies for planning the development of your garden during this planting season: develop a short list of plants, install significant numbers of each kind of plant, and select some unfamiliar plants that will fit into your plan and provide a fresh new look to your landscape.

Enjoy this fall’s planting season, and your garden’s coming spring!

The Ageless Aeonium

Today, we introduce the genus Aeonium, which includes 35 species, most of which are from the Canary Islands, northeast of Africa.

These plants are characterized by the development of rosettes of leaves on basal stems, i.e., stems that rise from the plant’s roots.

The generic name, Aeonium, comes from an ancient Greek word that means “ageless.” In fact, for most species, the rosettes die after producing a flower, although the entire plant lives. A few species are monocarpic, meaning that they produce a single rosette without a stem, and then the entire plant dies.

Popular Cultivars

  1. A. ‘Zwartcop’ (Black Rose), a cultivar of A. arboretum, develops rosettes with very dark reddish-purple, almost black leaves, on stems that can rise to four feet. This plant produces effective displays in the landscape or in a mixed container, especially when contrasted with yellow flowers like those of the plant’s own blossoms.
  2. A. ‘Sunburst’ (Copper Pinwheel), a cultivar of A. davidbramwellii, is a variegated form, with large rosettes with variegated green and white leaves edged in bright, coppery red. The stalks rise up to 18 inches. ‘Sunburst’, like other variegated plants, can provide pleasing contrast in the garden.

Aeonium 'Sunburst' best

  1. 3. A. nobile (Noble Aeonium) produces a single, stemless rosette up to nearly two feet in diameter, making it entirely distinctive among the aeoniums. The leaves are yellowish, with a reddish edge when grown in bright light. This is one of the monocarpic aeoniums: it dies after producing its reddish blossoms.
  2. A. tabuliforme (Saucer Plant, Dinner Plate Plant) is another monocarpic aeonium that provides a single, unique, nearly flat stemless rosette.

Cultivation

Aeoniums will be dormant during the summer months and resume growing in the early autumn.

They are very easy to grow in containers, where they flourish with their shallow roots and occasional watering. Use a normal potting soil, rather than a fast-draining cactus mix. In the Monterey Bay area, they prefer bright morning sun and afternoon shade. Fertilize only when the leaves become yellowish, indicating nitrogen deficiency. Too much fertilizer will promote too-rapid growth and weak stems.

When grown in the garden in this area, aeoniums require little care. As with container plants, avoid very rich soil and fertilizers.

Propagation

All aeonium species and hybrids can be propagated from seeds, but most are propagated easily from stem cuttings. This might be done to produce additional plants or to bring a rangy plant into a more compact form. During the plant’s normal growth period, from autumn to mid-spring, cut a rosette with up to five inches of stem (shorter for smaller, shrub-like forms) and place in a cool shady place for at least three days, to heal over. Then, place the cutting in a normal potting mix, in a small container, and in a shaded, windless location to reduce moisture loss. After the plant has established roots, place in a container or in the garden.

The monocarpic species are not propagated from stem cuttings, but from leaf cuttings, which are more successful with A. tabuliforme than with A. nobilis.

Aeoniums are drought-tolerant plants that are easy to cultivate and interesting additions to the garden.

Updating the Landscape

August might not be the best time of the year to work in your garden.

Even the Monterey Bay area’s temperate climate can be uncomfortably hot for digging (if that is among your priorities).

The early morning hours can be a fine time to keep up the chores, but using that time presumes readiness for an early start and control over the day’s schedule, which is not everyone’s situation.

Still, the lazy days of summer include opportunities for creative advances in the garden.

A priority task that is too often neglected, and could be pursued now in a timely way, is the annual assessment and adjustment of the home landscape.

The assessment process can involve a slow inspection walk through the garden, but ideally includes choosing a vantage point where a comfortable seat and a cool drink will support appraising each significant plant, and envisioning the renewal of the landscape.

Screen Shot 2015-08-15 at 11.01.27 AM

Take a little time for this important task, which can guide progress during cooler days, which are not far off, and chart longer-term improvements.

Right now is also a good time for your review of the landscape because in about two months, with optimism, we will begin our rainy season. At that time, we should have new plants in the ground, because the rains will keep them watered as they become established.

This review presents a good opportunity to recruit a fellow gardener to provide a second opinion. Invite reciprocal visits with someone who both respects the current restraints on your time and resources, and brings a creative perspective to the process.

When appraising the landscape, look for…

  • Plants that have been neglected, and consequently are struggling, dying or already dead.
  • Plants that are overgrown, and have begun intruding on walkways or crowding other plants.
  • Plants that need dividing to perform well. (Dig and replant irises this month and next.)
  • Plants that were misplaced originally, and would look better in another spot.
  • Areas that would be improved by the addition of a new plant of a particular size, blossom color or form.

The last appraisal listed above will require study to identify the right plants for addition to the garden. This could involve visits to the local garden center, or reviews of printed catalogs or websites. A neighborhood stroll is always a practical approach to finding plants that would work well in your garden and flourish your local growing conditions. When you see a desirable plant, ask the homeowner to name the plant so you could search the web for its cultivation needs.

Summarize the findings of the appraisal in a task list with target dates for needed adjustments.

Regular reviews and adjustments of your landscape will keep it looking fresh and interesting. Such reviews could be done annually, as proposed here, or at the beginning of each season.

Our gardens please us because they are alive and always changing, so gardening succeeds best when gardeners interact with Nature.

Water Storage Tricks

With our persistent drought, and the possibility that it signals a long-term change in our climate, gardeners are becoming interested in succulent plants. They warrant a closer look.

All plants store moisture in various parts of their anatomy. Succulent plants store more moisture than plants in general, having adapted to surviving in areas of irregular rainfall.

Succulence is a characteristic of plants, rather than a taxonomic category. As a result, identifying succulent plants can be an arbitrary exercise. For example, some gardeners will group succulents apart from geophytes and cacti, although both store moisture. That’s OK, because “succulent” is not a formal definition, but it’s still appropriate to think of geophytes and cacti as good at storing moisture.

Succulents are found in about sixty plant families, and a wide range of genera within those families.

One unusual group of succulent plant is the caudiciforms, which store moisture in a caudex, which is a woody stem structure that typically develops just under the surface of the soil. Gardeners who enjoy growing these caudiciforms in containers often adjust them to display the caudex above (or partially above) the soil surface. The caudex, also called a “lignotuber,” is not attractive in the conventional sense, but by any name it is an ingenious adaptation of the plant to unreliable moisture conditions.

My garden includes two caudiciform plants. One is a Ponytail Palm (Beaucarnea recurvate), from Mexico, which is not really a palm. The cultivation advice for this plant is to never water. This might seem harsh, especially for gardeners who equate watering regularly with nurturing the plant, but it indicates that the plant is epiphytic, meaning that it derives moisture and nutrients from the air, rain, and sometimes from debris that accumulates around it.

Ponytail Palm

Ponytail Palm (Beaucarnea recurvate). Click to enlarge the photo, and make more visible the caudex at the base of the plant.

Screen Shot 2015-08-02 at 8.30.44 PMMy other caudiciform plant is a Beautiful Serpent (Agapetes serpens), which is from the Himalayan mountain range north of India. It is in the Ericaceae (Heath) family. The plant’s specific name refers to the snaky growth of its stems, but its blossoms are more distinctive, in my view.

 

I have not seen the common name, Beautiful Serpent, online, but that’s what I call this plant.

Screen Shot 2015-08-02 at 8.31.19 PMMy plant is A. ‘Ludgvan Cross’, which is a cross of A. serpens and A. rugosa, both from the Himalayas. This hybrid has distinctive chevron markings on the blossoms.

 

Both photos of Agapetes serpens are from Strange Wonderful Things: Rare and Exotic Plants which is a fine website for gardeners to visit.

I found this rather rare (or at least uncommon) plant in a local garden center, then found online cultivation advice that emphasized bright but cool conditions, with protection from the afternoon sun. This seemed appropriate for a plant from the Himalayas, so I put in a container of about 1.5-gallon size, filled with good potting soil, placed the pot in a bright shade location, and watered it regularly.

The plant grew well enough, but has produced few stems and blossoms, compared to photos I have seen online. It didn’t seem happy.

With a bit more research, I learned for the first time that this plant is a caudiciform. The caudex is below soil level, so this was a surprise. Then with further research, I learned that it is also epiphytic! This is a game-changer.

Not all caudiciform plants are epiphytic, but they use available moisture very efficiently, so irrigation should at least be limited.

My cultivation plan for this plant now involves keeping it in the same bright shade location, and discontinuing irrigation. Reportedly, it prefers humid conditions, so I might mist it occasionally.

The first takeaway from my experience with this plant is to find more than one source of information on unusual plants that you bring to your garden. The Internet holds an amazing wealth of information of value to gardeners, and we should draw upon it routinely.

An important first step in researching a plant is to learn its botanical name. A search based on a common name often will lead to good information, but the botanical name is more accurate and preferable.

Try one or more caudiciform plants among the succulents in your garden. A rich source of information on these plants is the website bihrmann.com. Hint: when you browse to the home page, click on the image immediately after “.com.”

Incidentally, you might enjoy exploring this website, which has many images of flora and fauna, in several categories. The author, identified only as Bihrmann, has travelled extensively, taken an enormous number of photographs and lived a rich life. Some of the pages are in Danish.

***

Summer Priorities

 

My first summer priority in the garden centers on weeding, and my regular resolution to walk around with a weed identification book. My desire to know the names of garden plants extends to the weeds that know so well how to grow under all conditions, and without nurture.

One new arrival is the Black Nightshade (Solanum nigrum), which is a relative of several desirable plants, including potatoes, tomatoes and peppers. It is common throughout California.

7-17-15 - Solanum_nigrum

This weed grows up to four feet tall. UC’s Integrated Pest Management website describes its leaves as follows: “The first true leaves are spade shaped with smooth edges and the lower surface is often purple. Later leaves are increasingly larger, egg shaped, dark green, often purple tinged, with a smooth to slightly wavy edge, and covered with short non-glandular hairs and some glandular hairs.”

The plant produces small, star-shaped white flowers that develop in blackberries about one-quarter inch in diameter. Some varieties have edible berries, but their taste is not good enough to offset risking that you have a different variety in your garden.

To its credit, the Black Nightshade pulls up easily.

Another member of the Solanaceae, the tomato, is also flourishing in my garden. This year, I planted two cherry tomato varieties from Love Apple Farm, chosen at San Francisco Flower & Garden Show. A volunteer from last season, ‘Sweet Million’, popped up, so with minimal watering, I have an abundant harvest of cherries for salads and casual snacks outdoors.

Then, a friend gave me a seedling of a Black Krim (Solanum lycopersicum), a heirloom tomato from Russia. This plant needs consistent moisture. If the soil is allowed to dry out between watering sessions, the fruit has a tendency to crack.

Tomato fanciers relish its “rich, salty flavor,” so I’m watching for the fruits to ripen enough for a taste. When fully ripe, the tomatoes are a dark reddish purple or brown (not truly black) and with dark green around the top, or shoulder.

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Black Krim Tomato Credit: www.gardenharvestsupply.com/

Another priority for the summer is mulching, which is actually a good practice for any season, whenever the soil is uncovered. Mulching discourages weeds, slows the evaporation of moisture, creates a good environment for soil microbes, and protects the soil from erosion.

Organic mulches are available in garden centers in bags of 1.5 or 2 cubic feet. For larger gardens, chipped material from a tree service is a low-cost alternative. Such material is coarser than commercial mulches, and consequently lasts longer.

A tree service will drop a load of chips on your property without charge, if you can receive it on their schedule. Another option is load a yard or two of chips into your truck, at the service’s premises. Call ahead!

A responsible tree service will not bring or offer chips from diseased trees, but otherwise the chips will be from a randomly chosen pruning project. All chips are good in the garden, but some are more aromatic than others. Think eucalyptus!

Finally, during these warm summer months, we can anticipate significant rainfalls this winter, based on the meteorologists’ assessments of the El Niño ocean conditions. Potentially heavy rains won’t completely end our drought, but it could help a lot.

***

Gardening’s Underlying Science

 


We appreciate our gardens for their beauty and natural vigor, even as we know, deep down, that each plant is a wonder of science.

Well, perhaps that thought hasn’t entered your thoughts, recently, but it’s still true.

You might think we don’t need to dig into the science behind plant growth, as long as we keep them fertilized and watered and they keep growing. That’s not necessarily true!

I’ve been gaining interesting information about the science that underlies garden plants. One of the very good sources of that information is horticulturist Linda Chalker-Scott, Ph.D. She has published fine research reports, taught a lot of university courses, and has communicated a lot of plant science to home gardeners through Master Gardener programs in the State of Washington and her writing.

Her writing for lay readers has been published in several books and periodicals, and on The Garden Professors, a blog on which she and several colleagues share their expertise and opinions. This website (http://gardenprofessors.com/) includes fascinating reports of gardening myths.

Misconceptions abound in the gardening community.

I first became aware of Chalker-Scott’s contributions through two of her books, The Informed Gardener (2008) and The Informed Gardener Blooms Again (2010).

Her newest book is How Plants Work: The Science Behind the Amazing Things Plants Do (Timber press, 2015).

The Informed Gardener

In How Plants Work, she presents basic concepts of plant biology: cells, roots, nutrition, photosynthesis, leaves, seasonal cycles, growth patterns, pruning and propagation. (This very brief list of the book’s topics doesn’t convey the depth of her presentations. See the book for the full information.)

Dr. Chalker-Scott has written these chapters with her well-established commitment to communicating her scientific knowledge to non-scientific readers. She has managed to present the science effectively without “dumbing it down.” Gardeners with limited backgrounds in biological science can understand and appreciate this information, but will have to stay focused and perhaps read some passages more than once. I certainly did!

The book addresses some gardening myths, which I find always interesting, but emphasizes the positive message: knowing “how plants work” is the foundation of successful gardening.

To encourage you to read this book, I will share one of the book’s gardening myths, and an example of its garden science nuggets about which gardeners should know.

Myth: Landscape fabric blocks weeds while letting water and oxygen to pass through.

Reality: These fabrics soon become clogged with soil particles, and block the movement of water and oxygen. Meanwhile, weeds become established on top of the fabric, and some aggressive varieties manage to poke through.

Science Nugget: All plants have primary compounds that are required for growth and development: sugars, DNA, fats and proteins. They also produce secondary compounds that defend against pests and diseases, or that attract pollinators, or have other properties that are currently unknown. Chalker-Scott describes several kinds of secondary compounds and reports that every plant produces one or more unique compounds, and that scientists know about less than ten percent of the compounds that plants make.

We think we know a lot about the plants in our gardens, but we have a long way to go.

***

Restoring Soil

Several people commented on last week’s column on the carbon cycle. All endorsed the concept of restoring garden soil, to support its natural ability to sequester carbon.

One reader had questions about how to go about restoring garden soil. This is a Big Topic and you, good reader, might have your own questions, but you also might share his interests. My brief responses are below. Visit gardening.com for more details, including plant suggestions.

Q. Plow the grass under?

A. Losing the thirsty lawn is a good first step, because such monocultures are not appealing to wildlife. Plowing, however, could both promote re-growth of the grass and bring dormant weed seeds to the surface. A better approach is to kill the grass over several sunny weeks by covering it with clear plastic (solarization), or with newspaper or cardboard (smothering).

For information on Soil Solarization for Gardens & Landscapes, visit the University of California’s Integrated Pest Management webpage on the topic. The presentation emphasizes pest control; in this context, unwanted turf grass amounts to a pest.

The California Native Plant Society has Detailed lawn removal advice.

Q. Plant different grass?

A. Yes! California native grasses can provide the basis of an attractive meadow, which is more casual than a manicured carpet of turf grass. A meadow has unique aesthetic appeal; supports a variety of wildflowers and wildlife; requires little water, infrequent mowing, and no chemicals; and helps to restore the soil.

Kids on Native Grass Lawn
JACQUELINE RAMSEYER —
BAY AREA NEWS GROUP

Lily Baker’s front yard in San Jose
features a native grass lawn.
California native grasses help restore the soil.

For information on several California native grasses, visit the Tree of Life Nursery’s web page, “Masses of Grasses.”

A very good book by Carol Bornstein, David Fross, and Bart O’Brien is Reimagining the California Lawn: Water-conserving Plants, Practices, and Designs (2011).

Q. Grow more trees?

A. Absolutely! Trees and large shrubs are attractive additions to the landscape, valuable participants in the carbon cycle, and welcomed by all forms of wildlife. Invest a little research to select trees will thrive in your climate, and grow to an appropriate size for your landscape. Again, California natives are good choices.

A good introduction to California native trees and larger shrubs is available from the non-profit Nipomo Native Garden, which has produced a web page, “Native Trees for Landscaping and Wildlife.”

Q. Eliminate ground cover in favor of something with deeper roots?

A. Ground covers are any plants that hug surface or rise to any height up to four feet. Most importantly, they protect soil and soil microbiota from baking in the sun, or eroding. During the fall and winter, plant seasonal cover crops that draw nitrogen from the air and store it in their roots. Examples of such “nitrogen-fixing” plants include peas, beans, and clover. In the spring, before your cover crop sets seed, till the plants under to decompose and release their nitrogen into the soil to support the growth of other plants.

Deeper roots mean better drought-tolerance: deep-rooted plant can find moisture far below the surface. Such plants are generally preferable in the landscape, all other factors being equal.

The depth of roots varies among plants, reflecting adaptation to the plant’s environment. Among weedy grasses, for example, Annual Bluegrass (Poa annua) has roots only about right inches deep, while Bermudagrass (Cynodon dactylon) can grow to 60 inches deep in search of water.

Infrequent, deep irrigation encourages all plants to develop deep roots and drought tolerance. A common error with automatic irrigation systems is to schedule frequent, brief periods of watering. This practice encourages shallow roots, ultimately increases overall water usage and leaves plants vulnerable to dry periods.

Q. Shallower roots?

A. The advantage of shallower roots is that plants growing in arid climates have immediate access to occasional rains. Succulent plants have adapted to such conditions by developing shallow roots and the ability to store scarce moisture in their leaves, stems or roots. For this reason, gardeners often appreciate succulent plants for both drought tolerance and landscape appeal.

The New California Garden, which we envision here, features meadow grasses and succulent plants: a good time to start is now.

Gardening to Reverse Climate Change

The threat of climate change has become a concern among scientists, environmentalists and gardeners (who might wear all three of these hats, of course). In the search for solution to this problem, these three interested parties have common ground, as we explore in this column.

As background, our climate is changing as a result of a disruption of the Carbon Cycle.

On Plant Earth, a fixed amount of carbon cycles through different forms: liquid, solid, or gas.

Carbon enters the atmosphere from several sources, including respiration of animals and plants, decay of animals and plants, eruptions of volcanoes, and releases of dissolved carbon dioxide (CO2) from the oceans.

Plants absorb carbon dioxide (CO2) from the atmosphere, and use photosynthesis to release oxygen back into the atmosphere and convert carbon into sugars that support the plant’s above-ground growth. At the same time, up to 40% of the CO2 goes to the plant’s roots, to feed soil microbes. The microbes assist the plant to acquire nutrients through its roots, and lock (“sequester”) carbon into the soil for very long periods.

The Carbon Cycle supports Earth’s climate and enables the growth of plants and literally all other living things.

Carbon Cycle

Credit: NASA/Globe Project

In the diagram above, notations in blue indicate pools of carbon and notations in red indicate fluxes of carbon, both quantities are measured in petagrams.

This complex natural process balances the amount of carbon in liquid, solid and gas forms. Vast amounts of carbon are stored in the soil and fossil fuels, and much smaller amounts are stored in the atmosphere, the oceans, and plants.

During the Industrial Revolution (1760 to c. 1830), humans began burning fossil fuels, cutting down forests, draining wetlands, converting grasslands to large-scale crops, paving paradise, and applying synthetic chemical fertilizers and pesticides. These activities have been disrupting the Carbon Cycle and altering this important balance.

The consequences include degraded soil with reduced ability to capture carbon, an excess of carbon in the atmosphere, the acidification of the oceans, and other effects, none of which are beneficial to living things (including us).

The broad term, climate change, encompasses all these negative effects.

Restoring the natural Carbon Cycle could reverse climate change.

Restoration requires feeding the soil with organic matter and planting cover crops to protect the soil from temperature extremes and erosion. In short, the solution is based upon regenerative, organic agriculture.

This strategy must be employed on a global scale, but we all should understand the Carbon Cycle and support this process of soil restoration in our own gardens and in our individual contributions to relevant public policy. Substantial private interests are invested in fossil fuels, “conventional” monoculture agriculture that depends upon synthetic chemicals, and other industrial methods that are changing our climate. They can be expected to resist this strategy of working with nature, so eventual success requires our vision and long-term commitment.

Each gardener could participate first in his or her own garden. That would be a fine way to celebrate our independence from, in this context, commercial interests.

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Agave: Another of Mexico’s Gifts to Gardeners

A recent column provided an overview of the genus Echeveria, called “Mexico’s Gift to Gardeners.” Today, we take a look at the genus Agave, another of Mexico’s gifts to gardeners, with value for larger settings.

Agave species grow naturally through the southwestern United States, Mexico and Central America, Columbia and Venezuela in South America, and the Caribbean islands.

All Agaves are monocarpic, i.e., they die after flowering. Unlike many annual plants, Agaves can grow for several seasons before flowering, setting seed and dying. For this reason have been called “multiannual.” They have also been called Century Plants, but they flower and set seed in much shorter periods, generally when conditions are right to support propagation.

There are two basic vegetative types of Agaves. One type produces offsets (called pups or babies) either in the leaf axils or through underground stems. The other type, called the solitary Agaves, propagates only by producing seeds.

These types are important for placement in the landscape. An offsetting type Agave needs ample space to allow for full development of a larger cluster of plants, while a solitary type Agave needs only enough space to accommodate its mature size.

Agaves generally consist of leaves arranged in a spiral, forming a rosette. The leaves might be thick or thin, succulent or fibrous. Some Agaves have smooth leaf edges, while others have sharp teeth along both sides of the leaf. Some species have leaves with terminal spines, which might be stout and quite sharp.

The rosettes come in several size categories, depending on the species. The smallest can be three inches tall and four inches across, and the largest can be ten feet tall and twelve feet across. Likewise, the flower stalks vary in several characteristics, including height that in some species, e.g., A. americana, can reach up to thirty feet.

There are over 200 species of Agaves. Of these, about 80 are found in gardens, and only about ten species are commonly grown. The typical home gardener in the Monterey Bay area will be familiar with three or four species.

Agave americana, which grows to large dramatic form, is widely cultivated worldwide for its ornamental value. The rosette of A. americana can spread to six-to-ten feet in diameter, and its flower stalk, as noted above, can reach thirty feet. At east six cultivars are available, with different patterns of white or yellow striping on the green leaves.

Agave_americana74

Agave americana ‘Marginata’

Agave attenuata gets its specific name from the leaves that shrink to a point. This plant has an unusually curved stem, which is revealed as leaves age and fall off. It develops a rosette of six-to-eight feet in diameter, and produces a flower stalk up to ten feet long. The stalk typically will reflex towards the ground, then arch upward again. This growth pattern gives the plant the common names, the Fox Tail Agave or Lion’s Tail Agave or Swan’s Neck Agave. Because this plant lacks teeth along the leaf margins, or terminal spines, it presents no hazards in the garden.

agave_attenuata_form

Agave attenuata Credit: Annie’s Annuals

Agave tequilana, the Blue Agave, produces large amounts of sugars, mostly fructose, in the core of the plant, making it particularly suitable for preparing Mexico’s well-known tequila and other alcoholic beverages. This plant can grow to over seven feet tall, and produce a stalk up to sixteen feet high. A. tequilana has as much landscape value as other Agave species, but is most widely grown commercially.

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Agave tequilana (Blue Agave)

 

Agave victoriae-reginae, known as Queen Victoria Agave, is a smaller plant, growing slowly to 12 inches tall and 18 inches wide. It is popular as an ornamental for its streaks of white on sculptured geometrical deep green leaves. The leaves lack marginal teeth, and sometimes have short terminal spines. The flower stalk, which can reach up to fifteen feet, displays reddish-purple flowers. This is the only solitary type agave of the species listed here.

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Agave victoria-reginae

Agaves are drought-tolerant, easily grown plants that can bring dramatic architectural forms to the landscape.