The blooming of an Amorphophallus titanum always causes a stir.
The plant, which is the largest flower in the world, grabs the gardening public's attention primarily because it can soar to a height of 12 feet. But to view this gem, which is native to the understory of the tropical Sumatran rainforest, gardeners must act quickly. The flower, which can take up to 10 years to appear, only remains open for 24 to 48 hours. After that, it collapses into a limp, sad-looking heap. Other reasons for A. titanum's draw are the weird shape of the flower and, depending on your tolerance for such things, its strongly unpleasant smell.
As the word Amorphophallus implies, the genus gets its name from the shape of the flowers, which resemble a misshapen phallus. A. titanum has earned the nickname corpse flower because its huge flowers smell like a rotting corpse or carcass — nature's way of luring in this plant's pollinator, carrion flies.
This spectacle has a different effect on plant specialists, not because of the plant's spectacular bloom but because it's a rare opportunity. "When A. titanum flowers, people are swapping pollen from all over the world to be able to set seed on their plants," said Tony Avent, owner with partner Anita Avent of Plant Delights Nursery at Juniper Level Botanic Garden in Raleigh, North Carolina.
The nursery and garden became the newest member of the planet's exclusive flowering Titanum Arum Club when their A. titanum flowered on July 6. Avent named the plant "Peter Grande" and created a live channel on the Plant Delights website so others could see it flower. The flower collapsed on July 8, but Avent plans to keep the site up indefinitely because it contains extensive historical and cultural information about A. titanum, including a list of every recorded blooming of A. titanum in cultivation, which took Avent three years to compile.
"We have actually had several offers of titanum pollen, and I said, no," said Avent, whose nursery is the last-of-its-kind in the United States to be owned by an international plant hunter who offers some of the world's most hard-to-find and unusual flora on a large scale. That's because he has a much bigger goal in mind than giving the world another A. titanum; he wants to create the world's first cold-hardy A. titanum hybrid for home landscapes.
"I'm going to cross mine with Amorphophallus albus because I want a hardy A. titanum that will grow outdoors. So, we saved pollen from our A. albus plant that was in bloom two weeks ago, and we're getting ready to create a really wild plant that will hopefully grow outdoors."
The first cold-hardy A. titanum hybrid?
Creating a cold-hardy A. titanum hybrid for home gardeners would be a huge horticultural achievement. In fact, it's a feat considered so impossible that few have even attempted it. The closest anyone has come, said Avent, was the Des Moines Botanical Garden in Des Moines, Iowa, which crossed A. konjac with A. titanium. In that case, all the seed came up as albinos, which aren't viable because they had no chlorophyll.
Until now, A. titanum has been grown almost exclusively by botanical gardens and specialty nurseries because of its size — not only are the flowers huge but the tubers that produce the flowers can weigh as much as 300 pounds — and because of the patience, skill and the specialized greenhouse conditions needed to grow it. Mature plants, for instance, need to be grown in at least a half barrel and require a sunroom or conservatory with a 30-foot ceiling.
Avent is convinced he can succeed where others have failed. His thinking is that the much smaller A. albus will impart its cold-hardy trait and hybrid vigor to the A. titanum without greatly reducing the size of the A. titanum. The result, Avent believes, will be an A. titanum hybrid that would tolerate winter temperatures of at least 0 Fahrenheit and that could be grown in gardens in USDA zones 7b and above.
"We are in new territory here," he says. "Our expectation — if the cross works and if the plants are hardy, which we think they will be — is that we could see something with flowers in the eight-foot range. It could be absolutely extraordinary if it works."
If all goes as Avent hopes, the seed from crossing A. titanum with A. albus will sprout in May 2019. After that, he said Plant Delights will grow the plants for four years and then select the most promising plants based on cold hardiness, vigor, petiole pattern and floral characteristics. After that, he thinks it would take another five years to build up enough inventory to have sufficient stock to offer them for sale to the public. So, if you live in USDA Zone 7b or above and are a patient person, mark your calendars for 10 years out.
As he sets out to invest a decade in the project, he knows there will be doubters, but he's not going to let that stop him from trying.
Proving the naysayers wrong
"We've been told this won't work. But we've been successful in many other things that people said wouldn't work," he says.
He thinks he can prove the naysayers wrong for several reasons.
For one, he's made another Amorphophallus hybrid that he was told would never pan out. "Last year, we crossed Amorphophallus dunnii, which is one of the hardy Amorphophallus, onto Amorphophallus henryi. Supposedly, according to all the books, that's not possible. But I've got a hundred plants in the ground that didn't read the books, and the plants are looking pretty incredible. That's why we don't let our plants read books! We will see the first flower on those maybe next year, maybe the year after. We're out there on the edge. There's not many people who are even thinking about doing something like this."
A second reason is influenced by another Amorphophallus project he's working on with A. albus that has produced promising results. That project involves A. albus and A. konjac hybrids he received from a breeder in Germany. "(The German grower) made these incredible crosses, and didn't have anything to do with them. We have had them now for five years, have made our selections and are bulking them up. Probably the first one will hit the market in another two-to-three years."
Not just for plant nuts
Not that many people are familiar with Amorphophallus.
"They came onto the market years ago in sort of an underground fashion," said Avent, who admits the genus will never be mainstream garden plants but he still wants to introduce the plant to new audiences. "We were probably one of the very early places to say, ‘Wait a minute. These are actually really cool garden plants. So, let's try to mainstream these things.'"
That’s been his focus since. "People would make fun of us and say, well, you’re carrying those really weird plants." His response was, "Yeah they are, but they’re fun!"
Even if you’re not a "plant nut" or you take offense at the flower, Avent says there’s a lot to love about Amorphophallus. He describes the foliage, for instance, as looking like a little palm tree. “A lot of people are into hardy palm trees, and this is basically a deciduous palm tree. If you don’t have too many hangups, the flowers are absolutely amazing. I tell parents, 'If you want to get your kids into gardening, give them an Amorphophallus. Let them take those to school on show-and-tell day. The teacher might write you a note, but it would be so popular with all the other kids.' What a great way to mainstream gardening."
How to grow Amorphophallus
While you're waiting on the giant version of this plant, you can try your hand at a more normal-sized project. There are about a dozen species that are cold-hardy that can be grown in the ground. Here they are with their lowest USDA zone included in parentheses: A. konjac (5b), A. albus (7a) and A. kiusianus (6b, at least), which Avent said are probably the three hardiest; and a group that than can take temperatures down to 0 F (7b): A. bulbifer, A. corrugatus, A. thaiensis, A. yuloensis, A. yunnanensis, A. napalensis and A. henryi and A. dunnii.
Outdoor and pot culture are different. Here's a brief guide to both, and detailed information on growing A. titanum can be found on the Plant Delights website.
Growing Amorphophallus outdoors
As a general rule, Amorphophallus are woodland plants. But, Avent advises, they are fairly tolerant of several hours of sun. "We grow A. konjac, A. albus and A. bulbifer in full sun, and they do absolutely fine. Now, that is in well-prepared soil. But if they can get some morning sun or open shade people are going to get much, much bigger and better plants than if they grow them in shade. The site also needs to have good drainage so the corms don't get soggy and rot."
One of the neat things Avent said home gardeners can do is double crop Amorphophallus with some spring-blooming bulbs. "They can put these in the same hole when they are planting their daffodils, tulips, etc. Once those bulbs die down, the Amorphophallus come up. And when those die down, the others come up. So, Amorphophallus don't take extra room because you are sort of double cropping. There are just so many neat things you can do with Amorphophallus, and you never run out of space because you can just tuck these in anywhere."
The corms can tolerate being frozen, but Avent says it's better to avoid this if possible. He recommends planting the corms so that the top of the corm is six inches below the surface of the soil. The corms will actually pull themselves down to the right level. Water regularly during the growing season if there are infrequent rains. When it comes to fertilizing, Avent said he never fertilizes any plant in the ground. Instead, he prefers to do that organically. "Mix lots of compost into the soil, and your plants will be happy as clams," he said. When they go dormant, don't give them any moisture other than what nature supplies with rain and melting snows.
Be aware that Amorphophallus re-form their corms every year. "The corm you have this year is not the same corm you are going to have next year," said Avent. "Each year a new corm forms, and it sucks all the life out of the old corm. It happens very early in the season, and most people will never see that." Consequently, the best time to transfer or divide an Amorphophallus in the garden is when they are dormant or just going dormant.
Growing Amorphophallus in pots
In pots, plant the corms so the top of the corm is just below the surface of the soil. As with outdoor culture, the corms will pull themselves down to the right level. Water regularly during the growing season. In containers, Amorphophallus are fairly heavy feeders. "We recommend a good slow release fertilizer, and think it is ideal, though some people like to go with a water-soluble fertilizer," said Avent. "Either one will work in a container."
Corms in pots want to be very dry during the winter, so Avent recommends taking them out of the pots and keeping them in a cool dry place where they won't freeze, such as on a work bench in the garage or even over-wintering them under your house. "We store a bunch of them in a crawl space," he said. "That works great, as long as you don't forget they are there." The bare corm can flower, he added, because the corm flowers before it puts down roots. Be aware that if the corms flower in a crawl space, the air conditioner will suck the smell of rotting flesh up into your house.
However you grow them, be patient
Because Amorphophallus are tropical and sub-tropical plants, they often will not emerge from dormancy until mid- to- late June. "That's why they will never be a mainstream plant," said Avent. "Everybody is in the garden centers in April and May, and most people are not going to buy a pot of dirt. If they bought one they would be calling back the first of May saying, 'I want my money back because the plant never sprouted.'"
Therefore, he contends, Amorphophallus are for people who understand that plants rarely cater to human desires. "It's got a mind of its own. It's got to be hot before it emerges. It's the nature of the beast. It wants to be out there when the pollinator is there, which are flies. And we all know that flies are very plentiful in summertime!"
Most Amorphophallus are thermogenic. "That means that the corms actually heat up to take that smell and push it out so the flies will come in and have sex with it. I mean, you're an Amorphophallus ... you are a pretty ugly flower. So, are insects going to come to you on their own? No! It's like if you had a really ugly house to sell, and nobody was coming to look at it. You could throw a big barbecue and throw stuff on the grill and all of a sudden people would just pour in who wouldn't otherwise come. It's the same way with an Amorphophallus. It's trying to attract those pollinators."