A Gardening Journal

White-striped Agave

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This succulent is strong in style as well as attitude.  The only thing more powerful than the central stripe?  Each stiletto-sharp spine.  The tip penetrates the skin easily, and the shaft is rigid enough and sharp enough to enlarge that prick into a gash.  Yipes.

 

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But what's occasional blood loss if you can have white-striped agave ornamenting your gardens?

 

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Too bad that this fearsome plant also needs some rather intimate grooming:  It offsets profusely, as well as sending out runners.

 

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The offsets and runners—let alone the scary spines—combine to make weeding or removal of spent leaves a nightmare.

 

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This oxalis will resprout in a week unless it's extracted roots and all, which all the basal growth makes impossible.

 

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The solution was to unpot the beast, and slice away the offsets as well as the old leaves.

 

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The repotting gave an opportunity to reset the entire plant.  The rosette was developing a serious leftward lean, and now it's more plumb.

 

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If I keep up on the weeding, as well as clipping off basal growth before it gets out of hand, perhaps I won't have to subject either myself or this agave to such radical grooming for a couple of years. 

 

Here's how to grow this ferociously arresting warm-climate beauty:


Latin name

Agave americana 'Mediopicta Alba'

Common name

White-striped Agave

Family

Asparagaceae, the Asparagus family.

What kind of plant is it?

Evergreen perennial.

Hardiness

Zones 8b - 11. 

Habit

Rigid and sword-shaped leaves, with spines as sharp as any saw and a spiked tip as penetrating as any needle.  They emerge from the center of a rosette.  Offsets crowd at the base, and pop up at the end of underground runners.  After many years, a single spike of flowers, the size, literally, of a flagpole, soars with perfect verticality.

Rate of growth

Growth depends on climate and habitat.  Slow as a container plant in cooler climates.  Medium or even fast in the climates it prefers:  Hot, sunny, and fairly dry year-round.

Size in ten years

Much smaller than the straight species, which can become a titanic presence five or six feet tall and six to eight feet wide.  The rosette of 'Mediopicta Alba' matures to about two feet tall and three feet wide.

Texture

Sculptural; the variegation is so bright and large that the plant has a modernist presence.

Grown for

its form:  Agave americana is living sculpture made of foliage, albeit with vicious spines that can rip flesh as easily as a knife, and terminal spines that can pierce to the bone.  The thick and rigid leaves are widely-spaced in an ever-unfolding rosette; the entire plant has the look of a single  gargantuan and bloodthirsty blossom.  

 

its coloring:  The leaves of the straight species are a striking steel-blue; each leaf of 'Mediapicta Alba' also has a broad central greenish-white section.  It extends from the outer leaf surface to the inner, ensuring that the stripe is always in clear view.  When the leaves are young and just unfurling from the center, only the outer surface is visible.  When they are adolescent, and held at a slant, the inner surface is visible as well.  The continual emergence of new foliage at the center forces older leaves farther and farther outward and downward to the horizontal, where only the inner surface is visible.  In addition to being ominpresent, the central stripe is wide: about two-third's the width of the leaf itself.     

 

its durability: Agave americana is native to Mexico, but with good siting and care it can survive Winters in North Carolina.  See "How to handle it" below for strategies to maximize hardiness.  It is fully tolerant of blazing sun, minimal rain, rocky and infertile soil, and high heat.  The species is cultivated as well as naturalized world-wide, outside in dry mild climates, and in containers and conservatories elsewhere. 

Flowering season

After many years, rarely fewer than ten or more than thirty, Agave americana blooms, sending up a spike so tall and so vertical it's known as a "mast" that holds thousands of small yellow flowers in dense flat tiers.  The spike is usually taller than twenty feet.  After the flowers mature to fruit, the mother rosette dies.  Offsets around the base of the rosette are known as pups; there are rosette-tipped runners, too.  Both survive, turning one generation's growth-habit, as a single rosette, into that of the next, a dense colony of daughters.

Color combinations

Although the yellow flowers couldn't be more prominent, it's such a long wait for them that they are irrelevant in planning congenial color schemes.  Instead, limit your considerations to the blue-and-cream foliage, which is a natural partner to almost anything: yellow, pink, orange, red, green, and white, as well as to saturated rose, burgundy, and indigo.  Perhaps least interesting would be to combine with other blue foliage, or even gray foliage; either the agave or those blue/gray partners are bound to look washed out in comparison to the other. 

Partner plants

Agave americana has such powerful form—and, in 'Mediapicta Alba', equally powerful coloring—that neighbors that are similar in either respect instead of contrasting will almost assuredly look repetitious and weak.  Avoid partners with grassy or iris-like habits, such as true grasses and iris, as well as kniphofias and phormiums and, of course, other Agave or Yucca.  Partners with a rosette habit are possible if their foliage is clearly soft and rounded; think verbascums and hollyhocks.  Rosettes of Onopordum, let alone spiny cacti in any form, though, would convey your interest in S&M horticulture. 

 

Instead, consider multi-stemmed plants that also appreciate the same sun, heat, and dryness:  Anything whose common name is sage or lavender or rosemary, as well as round-leaved sunlovers such as Helichrysum, Crassula, and Portulacaria.  Woody species are a particularly good match.  Carissa, Cercocarpus, Eucalyptus, Laurus, Pittosporum, and (if you gave it soil that is more moisture-retentive) Buxus would all be congenial.  Conifers are foolproof, too, because their foliage will look feathery and soft regardless of whether it's actually stiff and needle-sharp.  There are species and cultivars of Cedrus, Juniperus, and Pinus that all succeed in the same sunny, hot-and-dry-in-the-Summer, mild-all-year habitat that Agave species and cultivars crave. 

Where to use it in your garden

Where hardy in-ground, Agave americana needs to be sited for the long-term.  The common name of "century" plant is hyperbolic by many decades, but any plant that can be expected to look, basically, the same for a decade or three can seem like it's been around forever. 

 

The plants are so sculptural that they can look out of place when sited where such a strong geometry isn't warranted.  Always locate Agave americana where it can function as a powerful focal plant.  Keep in mind that the rigid leaves can't be restrained, repositioned, or pruned except by being amputated.  Allow for the plant's maximum size and then some, to minimize chances of a painful or even dangerous encounter with the merciless spines.

 

If kept dry in the Winter by growing in extremely well-drained soil and protected from most of the cold-weather precipitation, Agave americana can be grown in permanently-positioned containers as well as in-ground, even where temperatures fall below 20 F.  Be sure the containers are unusually durable.  This dangerously-spiny plant is awkward to repot, and only gets more so as it gets larger with age.  The thick leaves store plenty of water, so plants are surprisingly heavy at any size.  This, in turn, makes handling them (or moving them into and out of shelter) all the more challenging.

Culture

Well-drained soil is essential in any climate, and is imperative in those that have a rainy season, let alone a rainy season that is also the cold season, when the plant is dormant and, therefore, too sluggish to fend off rot.  Tolerates part shade in mildest climates, but full sun is preferable, and is essential north of the plant's native subtropical and tropical habitat.  Growth is faster in fertile soil, but be careful that such soil is all the more sharply-draining.  Fertility is usually the result of increased organic matter, which is normally moisture-retentive and, therefore, could put the plant at risk of rotting. 

How to handle it

Rarely is a plant so dangerously spiny that "How to handle it" needs to be interpreted literally.  When working with Agave americana, wear heavy leather gloves and, weather permitting, heavy overclothes.  If I had a collection of such similarly spiny plants, not just a couple, I would invest in some sort of leather long-sleeved shirt, which would be a bit cooler to wear when handling the plant than wearing a Winter coat.  Potted specimens that need repositioning or, as in this article, repotting, need to be approached and then manipulated with unswerving focus and concentration if blood loss or even gashes are to be avoided.

 

If growing directly in your garden, plant in Spring so the Agave can establish during the heat of the Summer.  Water once, a week or so after planting, and unless your climate is truly rain-free for the warm months, during which you might water once a month, that's enough.  Established plants need no supplemental water, but will grow faster if watered and fertilized monthly during the hot season.

 

Old leaves eventually turn brown and die, but remain attached to the rosette.  Wearing appropriate protective garb, sever them as close to the core of the rosette as you can.  Maddeningly, access to the base of the leaves is all the more awkward because of the bases of other leaves nearby, let alone the rosettes.  Think of yourself as a surgeon, and come prepared with an array of tools; depending on the leaf and my patience, I've used loppers, pruners, a serrated steak knife, and a small folding saw.      

How to handle it: Another option—or two!

Containered plants need to be moved into shelter where the climate is colder than Zone 8.  In Zone 8 and the colder portion of 9, this might only be to move them under overhead shelter so that the plants stay dry in the cool season, which maximizes hardiness.  Colder than Zone 7, Agave americana needs to be moved to an enclosed and frost-free (but not necessarily warm) shelter.  These sun-loving succulents are unlikely to stay in active growth if they receive anything less than the stronger light that conservatory glass can transmit, and the high heat that is usually affordable only by institutions.  Only if your circumstances are that generous will the plant stay active over the Winter, and will welcome a light watering every month or so. 

 

If, like me, the goal of your overwintering is solely to keep plants alive, not to keep them in active growth, your shelter will probably be cooler at night, and will not have supplemental lighting.  In this case, withold water from when the plant was brought into shelter in early Fall all the way to February, by which time days will be longer and the sun will heat up your shelter, at least during the day.  Water moderately, but only once a month, until placing your Agave outside when frost danger is past.  Place in full sun and all possible heat.

Quirks and special cases

Although 'Mediopicta Alba' is sometimes described as being slow to offset, my experience is the opposite.  My plant produces pups and runners steadily.  Thankfully, the delicate chore of sliding the plant out of its pot and slicing them off isn't necessary more than every couple of years.

Downsides

The spines couldn't be more effective at damaging human flesh.  Grooming the plant—from removing older leaves, pups, and runners, to weeds that will inevitably colonize around the rosette—is a challenge.

Variants

Many!  The species itself is a stunning blue monster, soon too large to handle in climates where it would need to be brought into shelter for the Winter.  There are many exciting cultivars, usually smaller than the species and so more practical for containers.  Habits can be squatter, with shorter but thicker and more widely-overlapping leaves.  Spines can be even more prominent, colorful, and lethal.  Foliage that has yet to unfurl is so tightly grouped that outer leaves emboss the inner.  The impression that older foliage makes on the younger remains visible (and palpable), and can be prominent enough to be a feature in its own right.  Variegation can be yellow as well as white, sometimes at the edge of the leaves, other  times in the center.  Some forms offset more eagerly, and so form ready colonies; others offset only reluctantly, preserving the sculptural form of the rosette better. 

 

There are many other Agave species, and hybrids among them, some with leaves as narrow as pencils, and some with trunks.  The genus is full of subspecies from specific locales, which may have greater hardiness.  Some are hardy in Zone 7, 6, and, in habitat that is exceptionally dry in the Winter, even Zone 5. 

 

Gardeners in climates where Agave species and cultivars are generally hardy could easily have a collection of dozens.

Availability

On-line and, where solidly hardy, at "destination" retailers.

Propagation

By separating of the pups and runners from the mother rosette, and potting them up individually. 

Native habitat

Agave americana is native to Mexico and the American Southwest. 

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