Hello Reptilegrrl! I will try my best to answer your questions and help you with your Xanthosoma plants.

"I have read that these are heavy feeders. About how often do you feed them? And what? Should I just feed them what I give my veggie garden and houseplants? I've been giving them some fish emulsion as I plant them."

As a fertilizing you can use regular 20-20-20 (diluted in water) and give them this fertilizing every 2 weeks during growing season. This should be good to them. I use this fertilizing with the plants that i cultivate in my plantations and beleive me they are monsters. Obviously they are cultivated in the ground.

In the other hand, i also use Osmocote 14-14-14 (pellet of slow release) in the plants that i have in my house (potted). And they grow like crazy.

The reason why i use 2 different methods with my plant depending on where they are cultivated it is only a matter of space and time. I use 20-20-20 diluted in water with the plantations because it is cheaper and faster to disperse in large scale. Then i use the slow realese with the plants in my private collection, just because that way i can save time. You can try any of these, or any other fertilizing that is well balanced. I have never used fish emulsion, but i have heard from a lot of people that use it with great results and success.

"Also, have you ever transplanted a large corm? I want to take the big plants with me when we move. They have corms more than a foot long and thicker than my arm. I am not sure how deep their root structure is and I don't want to damage them in moving."

Yes! I have taken out of the ground corms of more than 18 inches long and 8 inches in diameter without any problem. I have removed all the roots, cut away the leaves (more than 8 feet tall)and then planted them in other places without problems.

You can do the same, obviously the plant will die or will be severly damaged, but the corm will produce a new main plant and several new plantlets. The corm will produce new plants as soon as it is planted in the new place. And even if you just throw the corm over the ground it will produce new plants that will become mature plants realy soon. Xanthosoma plants are a very prolific and strong, as long as good conditions are granted, like warmth and high humidity.

"The largest plant is infested with whiteflies. I've treated it a few times with insecticidal soap, but as soon as the whiteflies are gone, thrips move in! Should I be more aggressive with the soap?"

I cannot give you any advice on this theme becuase i have never had this problem. Maybe you should use a stronger insecticide.

If you have more questions, feel free to make them, i will galdly help you.

By the way, here are a couple of pictures of some X. violaceum in the wild on my lands:
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Have a great evening,
Jorge Joel...
Emilia's Garden

Hey, there, Jorge and Reptilegirl! I have another question about Xanthosomas - do they like a lot of water, like Colocasias, or to be kept on the dry side more like Alocasias. I have Lime Zinger, Mickey Mouse, and get this, I planted two malanga tubers - they were the purplish ones (which I think are going to be violaceum) that are now coming up.

BTW, Reptilegirl - if you want to try some from tubers, you can buy them at the Asian market as malanga tubers. There are the white ones, which is probably atrovirens, and the purplish ones, which are more likely violaceum, or could be sagittafolium.

Susan

Hello Susan! Well... My answer is not from the academy, but from my own experience. I cultivate most of my Xanthosoma in the drier range (all of those in my plantatins and most of those that i have in my private collection), like Alocasia species. But i also have several of them planted in the mini-swamps where i cultivate my Carnivorous Plants.

Results:
The ones cultivated in dry sites are mosnters, they grow very fast, the sizes are huge, multiply like weeds and produces lots of inflorescens.

The ones cultivated in the wet sites grow very slow, they take long periods of dormancy, do not produce inflorescens and they are very little, like miniatures, which is very usefull to me in my mini-swamps of CP's.

Conclusion of my observations:
They prefer the dry range. Obviously not dry as a cactus, but not wet like in a bog or swamp.

About the species you mention, you can also find "Malanga" or better called "Yautia" in Hispanic markets also. Here are the Spanish names that can be useful:

X. violaceum: "Yautia lila" (the tubers are lilac or purple[lila])

X. sagittifolium: "Yautia blanca" (the tubers are white [blanca])

X. atrovirens: "Yautia amarilla" (the tubers are yellow[amarilla])

As for what i know and speaking Spanish as my first language "Malanga" is Colocasia, Xanthosoma is Yautia.

Cheers,
Jorge Joel...
Emilia's Garden

The malanga tubers I bought are actually Xanthosomas, and they sell the colocasas as taro in the supermarket (Asian) here. They do not distinguish the variety of malanga, they just sell them as "purple malanga" or "malanga", which is the yellow. So far I haven't seen the white, which are supposed to be larger and smoother tubers. I guess you have to kind of know what you're shopping for before you head out, or be surprised when they come up. I don't think they have any Hispanic markets in OKC yet, but there is a huge Asian district. I have the yellow tubers, which are atrovirens, the most commonly found.

Sometimes you can find the Imperial Taro, which is C. Illustris.

I haven't grown the Xanthosomas yet, so I wasn't too sure about their culture. I have a lot of Colocasias and Alocasias, Remusatia vivipara, and a couple of Arisaemas, arums, and typhoniums. And I also am growing some callas this summer.

This is my second year of growing aroids, except for A. macrorhiza that I've had for about 4 years now.

Thanks for the help!

Susan

Hello Susan! ;0)

Yes, in most markets that sale tubers for food you will find only tubers called Malanga... Malanga this color, Malanga that color... And if you see that it is called Taro... that is an even wider name. And that is the problem as you say, because Malanga is a common name that is used indistinctively and so widely. Under the name Malanga you can have several different species of Xanthosoma and several Colocasia. Which obviously is a problem to the customer who buys the tuber, not for food, but to have plants for a collection. At least in your area they have a distinction between Taro and Malanga.

One thing i do is to take off a little piece of the skin of the tuber and see the color inside, that way i can be sure what type of tuber-speacies i am buying. But at least i have the advantage than in Hispanic markets they do distinguish from Xanthosoma and Colocasia, and depending on the color, you know the species. Maybe it is a matter of the languge. But since you do not have Hispanic markets on OKC, my advice to you is to check the color of the tubers;0)

So my friend, give it a try to Xanthosoma, they are really lovely. You will enjoy it;0)

Have a great day,
Jorge Joel...
Emilia's Garden