I had shifted this more to the direct sunny area as I find the earlier location seemed to keeping these leaves in more of a green shade instead of black tone. Also I had repot them into a bigger - deeper container where there is more room for them to grow.
They had doubled up the size in these full sealed pots - Actually I just used whatever containers I can get my hands on (buckets, recycled paint containers and plastic food containers - all without drainage holes underneath them)
The reason is they do require muddy-like medium where water is stagnant. Without water - the leaves will get burned and dried up.
Also occasionally I placed a teaspoon of Epsom Salt into the container about 2 week once. I have heard comments from some gardeners who use 1 or 2 handful of Epsom Salt into their pot too - but I rather take is slow and steady.
Some of these foliage have a slight green tones due to the rainy season where the days are very cloudy and rarely the sun shine few hours in a day. These days - these leaves revert back to green - like they were planted in shaded area. I'm not too sure whether the fertilizer too have a play on the coloration as I noticed that when I apply the fertilizer - they do perk up in vibrant dark colors too.
Perhaps both play in their part too.
I'm glad that these are doing so fine that I have managed to separate them into few pots and even have given a good size plant for an exchange with other plants. I would consider them hardy once they had established themselves - they tend to put out runners that grow new plantlets once it touch ground (when it is able to self-propagate in new areas)
I had also managed to grow one in total shade and see how it is doing - it appears that it can also grow well in shade but it will be more in green and no appearance of any black tones on them. Also it can handle total aquatic setting very well. I had placed it into a fish container and it is doing fine (minus the colors)
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For Other Different Types of Colocasia: