Re: Alocasias

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Dear Peter,

          Do you have any thoughts about the difficulty of cultivating A. robusta?  I got one growing nicely in a 10” pot, but on planting it in nice, leafmouldy, well drained soil, it went into reverse and disappeared. Of course I couldn’t grow it to maximum size in a container.

 

John.

 

 

Dear Alison,

 

It is my belief that even in the wild forest Alocasia often go through periods of boom and bust; with the plants reaching a peak of physical perfection and the  often soon afterwards ‘crashing’; the cycle in the wild seems to be ameliorated by the rejuvenation induced by regular leaf fall, but in pots there is a real danger that the pieces of the disarticulated rhizome do not get the chance to rejuvenate before they run out of stored carbohydrate, and then seem to lose the ability (will?) to re-grow.

 

Another factor that is only now becoming clear is that Alocasia, and many other terrestrial aroids too, I suspect, have some mycrorrhizal association. I first began to suspect this on finding super-vigorous specimens with infeasibly small root systems in the wild. Clearly the roots were too small to support the nutrient uptake that the plants needed, and yet the plants were thriving. The point was reinforced by observations of litter-trapping Schismatoglottis, notably species in the S. barbata complex, where investigation of the leaf litter revealed copious fungal hyphae and significant composting of the oldest leaf litter, with the plants rooting from the stem and through the leaf bases into this composted material and the decomposing leaves above. From our experiments we have observed a beneficial fungal population developing in the leaf litter within a couple of months, and a notable increase in plant vigour at this time. In fact, we no longer apply fertilizer to our plants (a considerable saving in time and money with ca 10,000 individual pots...) and this despite the fact that the nursery receives 5+ m of rain per anuum, and thus the flow-through of nutrients from the pots must be considerable.

 

On the subject of watering, our plants get watered every day, either from our virtually daily torrential downpours, or, in ‘dry’ periods from overhead sprinklers. Even in dry periods humidity seldom drops below 70%. The key is well-drained media and making sure that the rhizome is not totally buried. The crucial thing is that the leaf litter layer should not become dry (leaves crispy). The leaf litter (topmost leaves) remain damp and the leaves flexible.

 

One note, once you get the fungal hyphae community underway, the leaf litter will decompose fairly quickly. We ‘top up’ the leaves regularly to ensure that there are always fresh leaves on top of the decomposing and composted ones.

 

Very best

 

Peter