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How to Grow Amorphophallus titanum

...the largest flower in the world

 

Plant Delights Nursery is one of the few mail order nurseries in the country that sells Amorphophallus titanum, the Titan Arum / Corpse flower, aka the largest flower in the world. We get a lot of questions from our customers about how to grow Amorphophallus titanum. We hope you find this article of growing tips for A. titanum useful. 

 Titan Arum is a specialty plant for dedicated and patient gardeners who have the perserverence to care for this giant for 10 years or more before seeing it flower. Although it is thought of as being difficult to grow, Amorphophallus titanum is actually fairly easy to care for but it requires years of dedicated and persistent attention. If that sounds like you, then you are the perfect person to own this special and exotic plant. 

Where can I grow Amorphophallus titanum? (i.e., What kind of container should I grow it in?)

This amazing species is a tropical rainforest plant...so most people will have to grow it in a container. The retail-size plants that we sell are 1-2 yr old seedlings that will grow to about 24 inches tall in their first year. So you should start with a 6" or 8" container. As the tuber gets larger, you should pot it up (be careful not to bruise or nick the tuber during transplanting or else it could rot). Re-potting is best done while the plant is in its resting period and the new container should be 2.5x wider than the tuber. The tuber should be planted deep enough in the pot (1" deep for small tubers up to 15" deep for giant ones) so that roots that form on the top of the tuber are well covered with potting mix. Eventually, after 5-10 years you will have a 30-300 pound tuber that should be grown in a half-barrel or even larger pot. You will eventually need a greenhouse, conservatory, or sun room with a 10'-30' ceiling to allow enough space for mature growth. The pot should be kept off the floor a few inches to prevent nematodes, fungus, bacteria or other pests from entering via the bottom of the pot. 

What should I expect when my Amorphophallus titanum goes dormant? (What's this I hear about a resting period?)

Amorphophallus is not programmed to go dormant in fall like most of the temperate zone plants that we are familiar with. As long as you keep it warm and watered, it will continue to grow for as long as 24 months (the older they get, the longer they grow before resting).  Generally your plant will almost always be actively growing - as one leaf gets old and dies another will develop. Sometimes during this transition you may not have any leaves for a few weeks up to 15 months.  Be careful not to over water during this time or you could rot the tuber.  Think of it as a resting period. Under-watering and exposure to cold air can both trigger an early and a long resting period. Also, after flowering, Amophophallus titanum may rest for several months before resuming normal leaf growth. 

How do I move my large Titan Arum pot?

When moving your A. titanum be careful not to damage the base of the leaf, this could provide an avenue for diseases that could rot the tuber. The leaf on a mature plant will be between 6' and 20' tall and a mature plant in a pot with sightly moist soil will weigh up to 2000 lbs so use a hand truck or a wagon.  It is best to move your A. titanum during its resting period.

What type of soil does Amorphophallus titanum need?

There are a lot of conversations on the web with precise soil recipes and care protocols that you 'must use' to keep your Corpse flower alive. Most of those recipes and protocols are vastly over complicated. Here at Plant Delights Nursery, we grow hundreds of A. titanum every year, so we definitely know how to grow them, and it is a much simpler process than many make it out to be. 

The potting mix needs to be well draining with lots of organic material in it with a pH in the mid toupper 6's. We use a commercial, bark-based, nursery mix. You can create your own perfect corpse flower soil with a store bought, well draining pine bark / peat based soil mix. It's that simple! No precise measuring needed...no long list of hard-to-find ingredients, no layering of materials...just use whatever you can get at your local garden center...as long as it is well drained. After the plant goes into its resting period, every 6 to 16 months, repot the tuber into fresh potting mix into a larger container. Take care not to leave the tuber exposed for very long during repotting as it will not tolerate drying out.

How much sun does Amorphophallus titanum need?

It is a rainforest understory plant, so shade to partial shade is needed. Bright indirect light is best. In full sun the foliage will burn.

How much water does Amorphophallus titanum need?

During active growth, monitor the moisture daily but water only if it feels too dry. Try to keep the potting mix consistently moist, but not soppy wet or bone dry. When the plant is in its resting period, cut back on the watering but do not let the soil dry out...it should be like a well-wrung sponge...just barely moist to the touch. We use the finger test here at Plant Delights Nursery...we stick our finger into the potting mix about 1.5 inches down and if our finger feels cool or moist, then we do NOT need to water. Signs that you are keeping your A. titanum too dry include a drooping leaf or a leaf with brown edges or a plant that enters a dormant phase after just a few months. Note that when the tuber gets large, the potting soil beneath it will tend to stay too dry unless you thoroughly soak the pot when you water.

How much fertilizer does Amorphophallus titanum need?

When the leaf is first expanding you can fertilize with a liquid fertilizer once per week (at the dose recommended on the package), and when the leaf is fully developed, fertilize with a slow release fertilizer such as Osmocote (we use a generic 16-8-6 granular fertilizer here at the nursery). No need to feed during its resting period.

What temperature does Amorphophallus titanum need?

The corpse flower will be forced into a resting period if exposed to cool temperatures. And prolonged cold temperatures (below 45F) will kill the plant. To promote growth for the longest period of time, the daytime temperatures should be around 80-90F and the night time temperatures should be around 75F. As the weather cools in the fall, move your titan arum indoors. The indoor air should have 80-90% humidity and 75-80F, so mist it or run a humidifier. Also, it is important to have good air flow, so have a fan nearby to keep the air circulating. This helps to minimize potential foliar diseases that could go systemic and rot the tuber.

 When will my Amorphophallus titanum flower?

If all goes well, in 8 to 10 years after you buy a retail sized Amorphophallus titanum you could get a flower. The tuber needs to be more than 33 lbs before it is large enough to flower. Patience is a virtue with this plant!  After it blooms, if it was not pollinated, it will continue with its normal leaf-growth cycle for another 7-10 years before blooming again. If pollinated, A. titanum frequently dies...but you can use the seeds it creates to start again. A. titanum is not self fertile so if you want to pollinate it, you will have to get your hands on someone else's pollen (good luck!) and hand pollinate the female portion of the inflorescence during the first night after the flower opens when the female parts are receptive. The massive flower is sadly short lived. After the second day the inflorescence closes up, collapses and starts to whither just 4 days after opening.

How can I propagate Amorphophallus titanum?

If you cannot wait for seeds, then you a have a few other options. 1-2' sections of leaf taken from the outside edge of the leaf and include a y-shaped vein can be rooted after dipping the base in rooting hormone and keeping it in a humid chamber for around 9 months. From these cuttings, a tuber will develop under the potting soil and new leaves will start to grow from that tuber. If you are more advanced, then you can try tissue culture using cell suspensions of leaf and tuber parts, a technique pioneered by Hans Kehlenbach in 1985.   

What types of pests bother Amorphophallus titanum?

Insects are usually not a problem. We sometimes see aphids on newly expanding leaves. A good blast of water or some horticultural soap takes care of them. Mealy bugs may also appear on the tuber, but are generally not a problem and can be carefully removed during repotting. Over watering or damaging the leaf stalk can promote root rot bacteria and fungi to attack the plant. That is easy to avoid with proper care. Root nematodes are sometimes a problem in botanic garden conservatories as they can easily pass from other tropical plants to the corpse flower...the nematodes damage the surface of the tuber and promote rot. 

Information about Amorphophallus titanum

In the wild it is found as an understory plant growing on steep limestone hillsides of the Barisan mountain range in the rainforests of western Sumatra, Indonesia very near the equator.  Temperatures, moisture, light intensity and day length stay fairly constant. In the tropical rainforest, the day time temperatures are 80-90 F every day. Humidity is always high...70-90%. Sumatran rainforests receive periods of daily rain (as much as 118 inches per year) which keeps things pretty moist and steamy. In the forest understory, the light levels are fairly low. This is the natural condition in which Amorphophallus titanum grows and is adapted to.

Amorphophallus titanum leaves grow to gigantic proportions for between 4 and 24 months before dying and being replaced by another. Young plants hold their leaves for only about 6 months while older plants hold them much longer.  A large leaf may be over 100 sq. ft. in area...really! In between leaf growth periods, the tuber enters a resting period when there are no leaves or other above-ground features. At the beginning of the growth phase, the corpse flower generates a single large leaf which swells to up to 8'-15' wide on top of an 8'-20' tall stalk. The single giant leaf feeds a large underground tuber. The tuber starts life quite small but it can double in weight during each growth period and after 8-10 years it can be gigantic...between 50 and 300 pounds and is larger than a basketball (20" to 40" in diameter)! 

Once the tuber reaches mature size (at least 33lbs) the growth phase begins with a gigantic stinky flower instead of a leaf...up to 8' tall and 5' wide and vase shaped. The flower smells like rotting fish, sweaty socks, and feces (aka, like a frat house) which attracts its preferred pollinators...flies and carrion beetles. After just a few days the flower is spent and quickly shrivels and dies. If you can get your hands on some pollen and you pollinate your corpse flower, then after flowering is complete the remaining flower stalk will be lined with hundreds of berry-like red fruits, each with a single seed inside. After flowering, the titan arum will rest for up to 4 months before resuming the leaf growing cycle again. The giant flower consumes lots of energy so mature Amorphophallus titanum tubers only produce flowers once every 7 to 10 years. The tuber will lose a lot of weight during the flowering phase and it takes years to recover this lost weight to be able to flower again.

If you buy an Amorphophallus titanum from us, we would love to hear about its progress...and send us photos too. If you succeed in getting your PDN sourced Corpse flower to bloom, we definitely want to know about it...we are proud grandparents after all! :)

 

References

Lobin, et. al. , The cultivation of Titan arum (A mor phophal lus titanum ) – a flagship species for botanic gardens, Sibbaldia No. 5, Pg 69-86 - A great reference geared towards botanic gardens and conservatories, but a little too much for a home grower.