March 30, 2006

Amorphophallus Bulb

Repotting Amorphophallus
My largest Amorphophallus konjac bulb, is really getting big!
Any gardener who has grown to become a plant enthusiast can remember, as a child exploring encyclopedias seeing rare plant photos from the past. Gardening in the nineteenth century often meant collecting terribly exotic plants merely for the wow-factor. Remember those grainy, black and white vintage images, with perhaps a little girl standing on a giant 12 foot wide Victoria water lily pad....or bearded men with long saws, proudly posed under a felled giant Californian Sequoia log, or a very proper British dude in tweeds and bow tie, standing next to a large wooden crate in an misty conservatory, next to whom stood a giant twelve foot tall Jack-in-the-Pulpit-ish inflorescence? Well, that is what grows from this dormant bulb that I now hold, above. Now if that's not cool, what is?

The genus Amorphophallus is gaining popularity with plant collectors, once again. They're fun to grow in the summer outdoors in pots, as many of the species are quite easy, and they can be grown anywhere in the country. Although they are tropical, and native to South East Asia, Borneo and the like; they are dormant all winter long, and the tubs that you must grow them in can just be pulled into a cellar or unheated garage where they can stay, nice and dry and not freeze.

I take my eleven species out from under the greenhouse bench every March, to repot and to explore. I love seeing how big the bulbs have become, it just seems like magic, some even multiply. Not all species produce giant flower, many are smaller, with inflorescence no larger than a human hand. The only caveat is that the blooms smell like rotting animals, but I think that just adds to the whole experience.

This particularly nice bulb is Amorphophallus konjac, the most common species and easiest to obtain. (try Plant Delights Nursery or eBay). Every year I re pot the bulb, remove it's many offsets to share with friends or toss, or even eat, since the bulb is immensely popular in Japan and Korea where fields of them are an important agricultural crop for producing a starchy flour to make Soba noodles with.

Amorphophallus grow differently that other bulbs, so you must plant the bulb accordingly: the roots do not come out of the bottom, they come out of the top of the bulb, and from the stem near the bulb. To plant a bulb, Find the largest tub that you can, I use 30 gallon nursery tubs. It plant in a regular potting soil, and set your bulb down deep about four inches from the bottom, and then place a soil less mix like Promix on top, the bulb should be about 8 inches or more deep. Don't water until you see growth, around May or June. Amorphophallus bulbs produce generally just one long beautifully mottled stem with an umbrella of compound leaves at the top, like a giant Jack in the Pulpit, another relative from the Arum family. Fertilize while the plant it growing all summer, weekly, with a tomato fertilizer so the bulb will grow large. Be certain that your Tomato fertilizer has a the last of the three numbers higher than the first too on the analysis (like 18-18-30), phosphorous and potash are what bulbs need to get giant.

It does take time for Amorphophallus bulbs to build up enough energy to bloom, but they are lovely grown for the foliage alone. A bulb may not bloom for three or four years if you plant a potato sized bulb. This bulb is four years old now, and I have hopes that it may bloom this year or next. The inflorescence on A. konjac can reach 3 or 4 feet tall, but this species isn't even close to the largest that we have. That honor belongs to A. titanum, which is one of the more challenging Amorphophallus to grow since it requires a faster draining soil mixture and warmer conditions. That inflorescence can reach 12 feet tall, and only a few have been successfully raised at botanical gardens where the event is always celebrated with T-shirts and all night vigils with champagne. You can do the same when yours bloom, we will! Say tuned.


  1. Thanks for the info. There's not much online about which side of the Amorphophallus bulb (corum) goes up when planting. It can be deceptive because the roots grow off the top at first!

    Do you have any ideas for germination? I find it is more efficient to do them on wet paper towels rather than in soil.

  2. Anonymous8:26 PM

    The bulb should be cut longitudinally so that a portion of the center of original bulb stays . Cover the cut portion with clay or cowdung slurry to prevent drying. The shoots grow from the top of the cut portion

  3. Anonymous10:13 PM

    I had a 4 yr old tuber to flower, it was the size of an orange and had a 3 foot flower. The smell is awful but the bloom is worth it. I have close to 30 species but have only had 2 to flower, paeoniifolius is the other one, and it stinks for one day, konjac can last several days, and the odor will linger in your home for a very long time (mine bloomed in S. WV in january.

  4. Anonymous4:41 PM

    If only I could find a site of exactly how to plant these written in plain, clear English that makes sense. Putting a bulb in dirt and not watering until you see growth? You can't say that without explaining how the hell that works.........

    1. Yep. Pot it up but do not water it. Eventually you will see the shoot coming up. Wait till you see the shoot emerging from the soil, then water it thoroughly. Don't water it again till the shoot is several inches tall then give it another good soak. Only when the green leaf becomes visible do you want to start watering it on a regular basis. Then keep it moist but not wet, but never let it get too dry. Once you get the hang of it it's pretty easy to maintain.

  5. When can I dig out the bulbs of a amorphophallus konjac? Do I do this now in autum or in spring. I have always done this in spring and then repoted them. My plants are just starting to die, so I was woundering can I dig out the new bulbs now, or should I wait. Thanks

    1. Stop watering it and let the leaf fall and dry up. Then dig it and store it dry. In a paper bag works well.

  6. Anonymous4:07 PM

    I just dug mine out after the plant died down after the frost. I generally just keep them in a cool dry location until spring and plant them out in my garden again.

  7. What if I live in Washington and want to plant some in the yard I know cold and lots of rain But any chance they may come back if I didn't dig them up I have so many of them And wanted to give it a shot What do you think

  8. Anonymous8:52 PM

    I started with two and one year later I have 24 plants.

  9. i recently got 2, presumably, amorphophallus prainii. the soil is loamy but not compact n it rains everyday. they're 4 feet tall and the bulbs are orange and bottle cap sized. i hope it grows well.


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