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.
 

 
 

Super Size It!
by Troy B. Marden - posted 05/09/17

 

 

 

 

 

 

 

 

In the background, Dahlia imperialis holds court over Ricinus communis, the castor bean. In October, the dahlia will produce 4-inch diameter pink or white flowers.

 


I love big plants! Whether I’m designing a large estate garden or a small courtyard, big plants with large, architectural leaves and sometimes stunning flowers always play a role. Keep in mind that the words “big” and “large” are vague terms and everything is relative. A plant that looks very large in the confined space of a walled garden may look quite small on a wide open 2- or 3-acre property. At the same time, a plant that is truly suited to a large garden may quickly overwhelm one that is less spacious, so do your research and choose wisely. Also consider that “big” may refer to the height of the plant (a particularly tall selection), the width of the plant, the size of its leaves or a combination of all three. A very wide-growing plant may be difficult to accommodate in a small space, but tall plants can be used almost anywhere, so don’t let the height of a plant scare you away! In fact, you’ll find that tall plants, even in small spaces, add a dramatic sense of layering and help to create that lush garden effect that we’re all after.

So what are my favorite super-sized plants? I’m glad you asked! Here are a few large-growing favorites that have graced my garden and the gardens of my clients for many years. Some are grown strictly for the foliage, while others also provide beautiful blooms. Some are annual, some perennial, a few are tropical and there are even some shrubs. There should be something for everyone, and I hope they whet your appetite for plants that might be outside of your normal comfort zone.
 

Arundo donax ‘Versicolor’
The green and white variegated form of the giant reed is always a showstopper in the garden. Looking like a cross between the most graceful ornamental grass and a giant bamboo, it is hardy to Zone 6, dying to the ground each winter and rocketing skyward each spring to a height of 12 to 15 feet. A much improved variety named ‘Peppermint Stick’ has cleaner white variegation that does not fade in the heat of summer, while a smaller and somewhat slower growing cultivar known as ‘Golden Chain’ has green leaves with yellow stripes and reaches a diminutive 7 feet tall instead of twice that!

 

Arundo donax ‘Variegata’ is a giant member of the grass family that can tower 12 feet above its garden neighbors.

 

Colocasia gigantea ‘Thailand Giant Strain’
Almost all of us have grown elephant ears at one point or another in our gardens, but I’d be willing to bet that few of you have grown anything as impressive as this giant from Thailand! Reaching a whopping 10 feet tall with individual leaves that can grow as large as the hood of a Volkswagen Beetle, for sheer garden bragging rights this elephant ear can’t be beat. In a mild winter, with good drainage and deep mulch, ‘Thailand Giant Strain’ has survived into Zone 6b, though Zone 7 is probably a more sure bet. Even in more confined spaces, this plant will stand head and shoulders above the rest and can easily be underplanted for layers of interest.

Dwarfing the plants around it, Colocasia gigantea ‘Thailand Giant Strain’ is one of the grandest of all garden plants with individual leaves reaching nearly 6 feet long by 5 feet wide.


Dahlia imperialis
Even the name sounds regal, and regal it is! Perennial to Zone 6b, large trunk-like stems that may reach 3 to 4 inches in diameter by late summer and autumn emerge from ground level each spring and quickly rise to heights of 8 to 10 feet or more. The large, pinnately compound leaves almost resemble an unusual palm tree or bamboo as they hover above neighboring plants. In late autumn – provided we don’t have an early frost – pink flowers appear atop the immense stems and bid farewell to the gardening season. A white-flowered form is occasionally offered by specialty mail order nurseries.
 

Ensete ventricosum ‘Maurellii’
Perhaps my personal favorite of all of the magnificent members of the banana tribe, the red Abyssinian banana is a showstopper in most any garden. Growing quickly in the hot and humid summers of the South, even a small starter plant can reach 8 feet tall or more in its first season. Green leaves are flushed ruby red and may reach gargantuan proportions up to 8 feet long by 3 feet wide in rich garden soil, though they’re usually just a bit smaller. These plants can be overwintered by cutting all of their leaves back to the trunk in autumn and then digging and storing the remainder of the plant (trunk and roots) in a frost-free garden shed or crawl space to be replanted the following spring.

A bold and daring tropical, Ensete ventricosum ‘Maurellii’ is also called red Abyssinian banana. Individual ruby red leaves may reach gargantuan proportions, nearly 8 feet long by 3 feet wide when the plant is well grown.

 

Hedychium species and hybrids
Also known as ginger lilies, these beautiful plants are hardy throughout much of the South. Some, such as Hedychium coronarium (white butterfly ginger) are even reliable into Zone 6. In my garden it dies to the ground each winter, though farther south it is evergreen. In late spring it emerges from thick, tuberous roots with the tall stems reaching anywhere from 5 to 10 feet in height, depending on the variety. The tropical-looking foliage is always a welcome foil for other garden plants. In late summer and autumn, butterfly or moth-like blooms emerge from fat buds at the top of each stem, their fragrance carried on the breeze throughout the garden. Other favorites include H. gardnerianum, H. ‘Dr. Moy’, H. ‘Tahitian Flame’ and many others.

Hedychium, or butterfly ginger, comes in a variety of sizes. Some of the most beautiful can reach heights of 8 to 10 feet by autumn when they produce exquisitely fragrant, butterfly-like flowers in colors that range from white to pink, yellow and orange. In Zone 7 and warmer, many are hardy perennials.

 

Hydrangea aspera subsp. robusta
This hydrangea is not for the faint of heart and is probably best left to the more experienced gardener, but for those of you who want a plant that is both showstopping and unusual enough to stump your gardening friends, it’s the perfect choice! Best suited to protected locations in rich, moist, well-drained soil, Hydrangea aspera subsp. robusta has large, felted, gray-green leaves that may be as long as 18 inches and 8 inches or more wide. Combine this with 12-inch-wide blue lace-cap flowers in midsummer and you have a plant that will have your friends and neighbors asking what brand of fertilizer you use!

The flowers on the “giant” hydrangea are no slackers, either! Approaching 12 inches in diameter, it is one of the largest blooms in the hydrangea family.

 

Kniphofia ‘Lola’
‘Lola’ is a giant in the world of red-hot pokers, but is still small enough to fit into nearly any garden. With an upright habit, ‘Lola’ stands 5 feet or more tall when in bloom and the individual, brilliant orange “pokers” may be as much as 18 inches long! Nothing will stop garden visitors in their tracks like a well-grown clump of ‘Lola’ in full bloom. Hardy to Zone 6b and one of the best kniphofias for the South, all it requires is good drainage in the winter and it will return to grace your summer garden with magnificent blooms for many years to come. And in case you’re wondering, the hummingbirds will wait in line and fight for their turn at the flowers!

Not all Kniphofia, or red-hot pokers, thrive in Southern gardens, but Kniphofia ‘Lola’ has proven herself for many seasons in my garden. Standing 5 feet tall in bloom with 18-inch long spires of brilliant orange-red flowers, ‘Lola’ is a hummingbird’s dream and a showstopper in the early summer garden.

 

Musa ornata ‘Red Jewel’
For those of you who are still convinced that “giant” plants don’t have a place in your garden, I present to you Musa ornata ‘Red Jewel’, a dwarf banana reaching only 5 to 6 feet tall, with slender leaves and stems that are not obtrusive in any way. In a very protected location, this plant has overwintered as far north as Zone 6b and should be reliably hardy from Zone 7 south. In late summer on mature stalks, brilliant jewel-like blossoms like the one shown here may emerge from the top of the trunk. In colder zones, this banana can easily be dug and stored in a frost-free place for winter. The perfectly perennial Japanese fiber banana, Musa basjoo, is also an excellent choice, but understand that with time it will grow extremely large, eat up a good chunk of garden space and is nearly indestructible (or removable) once it gets established.

An excellent choice for smaller gardens, Musa ornata ‘Red Jewel’, the red jewel banana is a smaller growing selection that reaches only 6 feet tall and has proven hardy to Zone 7 in protected locations.

 

Petasites japonicus ‘Giganteus’
This plant is just too good to pass up, but I will issue fair warning that it does spread – rambunctiously – by underground stolons. That said, if you have a large, open area, especially a boggy spot where nothing else will grow, here is your plant! Like something out of Jurassic Park, petasites emerges each spring and quickly unfurls humongous leaves that may reach as much as 3 feet wide on stems 3 feet tall. Its texture in the garden’s understory is second-to-none and you almost can’t help but think there must be some sort of exotic, prehistoric animal lurking under its ground-covering foliage.

For damp locations, Petasites japonicus ‘Giganteus’ makes a stunning deciduous ground cover. Site this plant carefully, as it is a rampant grower and will quickly run over smaller plants that are in its way. Where you can let it romp, it adds a prehistoric flair to the garden.


Podophyllum pleianthum
If you love the strikingly bold texture of the petasites, but prefer a plant that behaves itself, then this Chinese cousin of our native mayapple may just be the plant for you. Glossy green leaves may reach as much as 2 feet in diameter on well-established clumps (this will take a while!) and unlike our native mayapple, it stays put! It is the perfect companion for other shade-loving plants such as hostas, hellebores and many others, and only asks that you provide it with rich, well-amended, woodsy garden soil. Other beautiful and even more unusual relatives include Podophyllum hexandrum, P. ‘Kaleidoscope’ and P. ‘Spotty Dotty’, among others.

Sources:
www.plantdelights.com
www.rareflora.com
www.hydrangea.com

 

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

 

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