I like to grow mine in Pro-Mix HP which is a very loose mix, ideal for this kind of a plant. As far as nutrients, I mix in some azomite, epsom salts, calcium sulfate, and fertilize with miracle gro every once in a while.

These are 2-3 gallon pots and the bigger one from the left is on it's 2nd leaf, still unfolding yet, visibly already the biggest one out of my batch, especially with the size of its stem which exceeds a foot in height. Once the new leaf gets to a certain size, the old one dies away.

I think as long as they are gradually hardened off into full sun, they should be fine outside as long as temperatures no longer dip below 45F. Their roots don't seem to like cold temperatures.

Here are a few more. The ones that are not producing their 2nd petiole appear to be fattening up their tubers, some already more than golf ball size. I know because I transplanted them up into their own pots, and the root systems are quite impressive using quality soil.

Thanks for the soil advice! You've got quite a collection of very healthy looking plants. I've been trying to keep mine Sumatran temperature, it is good to know I can move them outside once the nights get out of the 30s and 40s.

FWIW... I'm using Russian (Ukranian?) peatmoss mixed about 3 to one with perlite, charcoal, and a bit of fine pine bark. I add blood and bone and dolamite and fertilize the growing plants about once a fortnight with "African violet" fertilizer. I use to add fine, clean sand, but it tends to slow down the speed with which the mix drains. The quicker the drainage the healthier they seem (also makes the bloody pots lighter! <G>). I also give my plants plenty of daily, natural sunlight through 40 to 60% shade cloth and provide a situation with good, natural air circulation.

Great information! Thank you. Sounds like a great mixture and I like the "light" quality of the mix as the darn pots are so big!

The pots are not all that big if you put in consideration the size increase these plants will experience through out the season. I prefer to have them in the same pot they will be in for the entire season unless they are sold to somebody else.

Here is the largest one on it's 2nd petiole which still doesn't look like it is that big in its pot, but looking closer up, it is developing its 3rd petiole which will likely be much bigger than the existing one making the pot pretty small even though it is already a 2 gallon size.

I've been going by the 3 times the size of the corm rule for my two corms. My almost 7 lb corm came in a 5 gallon pot but I repotted it in a 22" diameter pot which is bout 2' tall. It is heavy! The corm seemed extra tall and narrow because of the pot it was in. This picture is it in the pot it came in , I cleaned it up

and put it in the bigger pot.

Thanks.

I think the size of the eventual corm is determined by how much leaf surface you get on your petiole given all other conditions being the same.

Some of mine that are only on their 2nd petiole look like they may already have tennis ball sized corms and there are still a good 3 months of warm weather to help them get even bigger outdoors.

Is it possible to force these guys to do dormant during the winter? I don't want to have tons of 2-3 foot tall plants on their 3rd petiole growing under my grow lights which have limited space.

My titanum has a rather interesting growth progression.

I purchased it as a one year old seedling one year ago. The plant has consistently produced new, ever larger petioles without going dormant. Up until now all the petioles that have been produced have been of the "juvenile" form. In the last three weeks the corm has put out three new shoots. From the appearance and size of shoot "B" as compared to anything it has produced before, this new growth will probably turn into a "mature" form petiole .

As you can see in the below photos the corm still has three juvenile petioles while in the process of putting up three more shoots! Shoot "B" is the largest and most vigorous of the three new shoots. "C" looks like another short stemmed juvenile and "A" is somewhat contorted and slow. The steel ruler in the photo is about 45cm long. This is all from a single corm.

My understanding is that they go dormant whenever they want though something I read somewhere suggested warmer temperatures cause them to go dormant. How long does it take a corm to go from having a little growing tip to a leaf. Seems like I have been staring for weeks at this little cone. Rob, that is amazing to have all those leaves at once, is the corm splitting?

Anne, I haven't been game to actually remove all the potting soil from the corm and check out what it looks like. My guess is that the multiple petioles are being produced by the single corm. If this beast ever goes dormant I will have a closer look. Since the plant has never stopped growing and producing roots, I've just transferred it to larger and larger pots while adding fresh mix to make up the difference.

I live in tropical Australia, but the altitude of my location (Atherton Tablelands) means that our winters can get cooler then are normally healthy for A. titanum. It's my guess that in its natural environment A. titanum's dormancy is probably stimulated by wet/dry seasonal variations rather then temperature.

That's one healthy plant you have there. I also live in a colder climate, extreme northern California on the flanks of Mt. Shasta. Will be interesting to see how the titanum does in out less humid climate. I have them in a bathroom for now but I know I will have to build a greenhouse soon, a cloud forest greenhouse is my dream :)

I forgot to add: It can and does take a fair time (a month or more in my experience) for that "little cone" to turn into a fully opened petiole. Even after the petiole fully opens out it continues to expand in height and girth.

Anne, It sounds like you have a real challenge there climate-wise when it comes to growing A. titanum. I spent quite a bit of time around Redding, California in my younger days, so I've got an idea of what you're up against... hot, dry summers and often bitterly cold winters. Good luck to you.

I have found that dormancy can be induced when the plant is stressed such as the petiole getting sunburned, the roots getting shaken up or the new petiole getting damaged as the old one is fading away.

A few consistent things I have found is that the ones that do get successfully adapted to full sun do appear to grow faster than those in partial shade. My fertilization regimen has been miracle gro, Epsom salts, azomite, and a bit of calcium chloride to supplement the promix hp mix which originally has little to no nutrients.

The amount and duration of natural sunlight does make a big difference in the titanum growth rates. I still tend to put a bit of shade cloth between "my beast" and our tropical sun as full sun here does tend to burn the leaves.

Ok, that makes me feel better, my little growing cone grew about that yesterday :)

Thanks for all your comments, helped me get an idea of what to expect.