Alocasia and Colocasia

Aqua Flora
Wed, 25 Feb 2009 13:03:07 PST
Dear Bob,

In addition to what has already been said, I'd like to add that Colocasia 
are hungry and thirsty plants! I grow about 17 different varieties of 
Colocasia all of them standing in water. Colocasia do not need to stand in 
water, and will grow happily under normal moist garden conditions, but will 
grow much bigger, better and faster if given lots of water.

Secondly, Colocasia prefer to grow in the full sun, most will also do well 
in partial shade, but many of the dark leaved varieties such as C. esculenta 
'Black Magic' and C. esculenta 'Midnight' tend to have a washed out colour 
when shade grown. Others like the dwarf C. fallax are much more shade 

Apropos Byron's comments on growth medium, Colocasia will grow very well in 
a rich compost-based medium, but as he rightly notes it will float out of 
the pot once submerged in a pond. The solution is to use a heavy clay-like 
loam / top soil / dirt / whatever you want to call it! You can use the same 
soil that is recommended for waterlilies and most other marginal aquatic 
plants. Personally I like to use equal parts heavy loam and composted bark 
together with a generous portion of bone meal and bounceback, this ensures a 
rich heavy medium that will not float out of the pot!

Lastly, the question of dormancy comes to mind. As most (if not all) 
Colocasia species originate from SE Asia, I think it is safe to assume that 
they do not require dormancy and will happily grow year round if you can 
provide adequate heat and light. But they will go dormant in temperate 
climates. Depending on how cold it gets they may be left outdoors where 
their leaves will die back, but the underground tubers will remain unharmed. 
Most of the commercially available varieties are reportedly hardy to Zone 7b 
(-12.3 to -17.7 C). From what I've read hardiness increases if plants are 
kept on the dry side during winter. In colder zones it is recommended that 
tubers be dug up in fall and stored in moist peat or similar medium in the 
basement. Fortunately I have a relatively mild climate and can leave my 
Colocasia in the pond year round where they do not go dormant but do look 
rather "ratty" during winter.

I might just as well add that there are approximately 8 species of Colocasia 
and many more cultivars. The ornamental varieties have become very popular 
of late, and as Byron noted Plant Delights Nursery does have a mouth 
watering selection of new cultivars from Hawaii. There is also a large group 
of culinary Colocasia (perhaps even more varieties than of the ornamental 
types). These have been cultivated in Tropical Asia since 5000 BC (some 
sources say 8000 BC), and is the oldest cultivated crop in the world! The 
starchy tubers can be boiled or the leaves can be cooked as a green 
vegetable. As all parts of Colocasia contain calcium oxide crystals, it has 
to be boiled for several minutes to render them safe to consume. Reputedly 
some varieties have better flavour and texture than others, but I must admit 
that I have never tried them ;-)

If anyone is interested in trading I have offsets of most varieties 

Bob, I hope this answers your questions!

Kindest regards,

Pieter van der Walt
(South Africa) 

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