Troy B. Marden is a plantsman, garden designer and co-host of Nashville Public Television’s hit gardening show, Volunteer Gardener. Troy’s gardens, photography and written work have appeared in numerous magazines and he lectures regularly on gardening around the country. Visit www.troybmarden.com.

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Get to the Point
by Troy B. Marden       #Ornamentals   #Plant Profile   #Xeriscaping

 

 

 

 

 

 

In this Zone 6 garden, Agave americana ssp. protoamericana survived several winters outdoors when it became too large to dig and move in from the garden each fall. A cage filled with dry leaves to keep moisture off of the plant during winter helped in its survival.

Have you ever visited California or the American Southwest and admired the beautiful agaves, or century plants, that dot the hillsides and grace the gardens throughout the region? Their subtle colors and stunning architectural forms are welcome additions to any garden, but being from the desert where dry soil and dry air prevails means taking a few extra steps in order to grow them successfully in the damp and humid South. Proper siting, soil preparation and in colder parts of the South, winter protection, are essential to growing agaves successfully, but the rewards are worth any amount of effort.


Agave parryiis available in several forms. Several are hardy to at least Zone 6b and will perform well in the garden as long as they have excellent winter drainage.

Dasylirion wheeleri has performed extremely well in the garden at UT’s West Tennessee Research and Education Center in Jackson, Tenn. It’s easily hardy to Zone 6 if it is well protected through its first winter or two.

 

The Cold Hardy Species
Not all agaves are hardy when it comes to surviving cold winter temperatures, especially in the Upper South, but there are a few species whose native habitats are at high elevations, making them very tolerant of cold winter temperatures and even snow! Some of the hardiest species include:

Agave havardiana
Agave lechuguilla
Agave neomexicana
Agave ovatifolia
Agave parryi
Agave parryi
ssp. Huachucensis
Agave toumeyana
Agave toumeyana
var. bella
Agave utahensis
var. kaibabensis


Agave parryi ssp. huachucensis is one of the hardiest of all agaves, surviving easily into Zone 6 as long as the soil is extremely well drained and the plant is protected through its first two winters until it is well established. Gravel mulch helps keep the base of the plant drier in winter.


How to Grow Hardy Agaves
The most important thing to remember when growing hardy agaves is that their cold tolerance is directly related to how dry they can be kept during the winter, especially for the first winter or two after they’re planted. In the South our winter weather patterns are often cold and wet for long periods of time and this combination can mean almost certain death for many species.

Agave ovatifolia is one of the most beautiful of all agaves and has fared better than most in the cold, wet winters of west Tennessee. Given the protection of a cloche for the first winter, the plants have been on their own ever since and are growing beautifully.

Proper soil preparation is extremely important. Jason Reeves, the horticulturist at UT’s West Tennessee Research and Education Center in Jackson, Tennessee has found success with agaves and other plants from the desert Southwest by thoroughly amending the existing garden soil with “turkey grit,” available from most farm and feed stores. Mix your existing soil at least 50/50 with the turkey grit and then apply a “mulch” of pure turkey grit around the base of the plant at least 1-inch deep. Because drainage is so important, you’ll find it beneficial to build low mounds of soil (6 to 8 inches high is sufficient) and to plant your agaves high in the tops of these mounds rather than digging holes and planting your agaves low, where water can gather and freeze around the crown of the plant.

Extra protection from winter rains is very helpful for the first winter or two. If your new agaves are small, this can be achieved by covering them with inexpensive plastic cloches, or bell jars, raised slightly off the ground by using bricks or wood blocks. These miniature “greenhouses” will help keep young agaves nice and dry during the winter until they become established — usually a couple of years. They can be found from several online sources. For larger plants, support rings — the kind often used for peonies and other perennials with gridded tops and three or four legs that can be pushed down into the ground — can be covered with heavy-duty clear plastic and placed over the tops of plants to keep them dry. The sides won’t be covered, but remember you are trying to protect them from rain and winter moisture. Cold temperatures, if you’ve chosen hardy species, shouldn’t be a problem.


One of the most beautiful of all hardy desert plants, Yucca rostrata ‘Sapphire Skies’ survives all the way to Zone 5, performs exceptionally well in the South and is an excellent choice for adding living architecture to the garden.

 

Not hardy, but very easy to grow, Agave attenuata ‘Variegata’ makes an excellent container subject and an easy winter houseplant for a well-lit room. It is perfect for a partly shady location in the summer garden, preferring less light than many other agaves.


Not hardy, but so beautiful that it is worth any amount of effort to overwinter it, Furcraea foetida ‘Variegata’ makes an excellent container plant or can be grown in the ground and dug and moved indoors for the winter. Its rubbery, spineless leaves pose less danger to the person whose job it is to move it in and out.
 

After the first winter or two, cold-hardy agaves should be established well enough to survive the winters without protection as long as the soil has been thoroughly amended and plants have been mulched with turkey grit around the base to help keep the crown of the plant dry.

In addition to thoroughly amending the soil for drainage, choosing the right site from the get-go is also important. Our natural instinct as gardeners is to plant these desert plants in the most open and exposed parts of our yard in full sun, but a protected location near the house, a wall, fence or hedge can also add to your success. Many of the hardy species of agave are found growing in the wild alongside scrub oak and pine, as well as shrubby desert plants that provide a bit of shade during the hottest part of the day.


Non-Hardy Agaves
In addition to the hardy species that are available for us to grow in our gardens, there are many beautiful species and varieties that make excellent subjects for garden containers during the summer months and carefree houseplants during the winter. I grow several species that are not hardy and that spend their winters in pots in front of a south-facing window in a barely heated utility room that stays cold, but doesn’t freeze. My favorite is Agave attenuata ‘Variegata’ because its spines are not as dangerous, making it easier to move in and out of the house and because of its reasonably small size, it can be kept for many years. Another favorite tender species is an agave cousin, Furcraea foetida ‘Variegata’, which also spends its summers outdoors and winters inside. It makes a large plant eventually, so be sure you have room to accommodate it once it’s full grown.
 

Agave Companions
Many hardy succulents, such as sedums, hens-and-chicks and others make excellent companions for cold-tolerant agaves, but some of my favorite companions — or maybe even substitutes for gardeners who aren’t ready to tackle agaves — are the many beautiful yuccas that are on the market today. Native to a wide range of climates, you can find yuccas of all sizes, shapes and colors that will thrive in gardens from Zone 4 to Zone 10. Some grow in large, ground-level clumps while others are trunk-forming and after some years will rise above the ground on stout stems. Variegated forms add even more interest to the garden throughout the seasons.

Agaves may not be for everyone, but for the adventurous gardener who loves to explore unusual plants, agaves can bring an entirely new dimension to the garden and their architectural form blends beautifully with many popular garden plants. Give them a try!

 

A version of this article appeared in a May 2011 print edition of State-by-State Gardening.
Photography courtesy of Troy B. Marden and Jason Reeves.

 

Posted: 03/12/18   RSS | Print

 

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