Friday, August 24, 2012

A little black magic

Little being the operative word.

I've grown the fabulously exotic Colocasia 'Black Magic' for a number of years now and it's normally one of the highlights of the late summer / early autumn garden.  By late August I expect to see my overwintered corms reaching about 30in / 75cm tall, potted into a large container, with foot long (30cm) leaves that emerge green and deepen to pure black within a couple of days and dangle from surprisingly stiff black stems, the whole producing a very effective, tropical looking foliage display.  Here's two views of the containers last August (posed in front of my Chaemerops humilis).  August the 17th to be precise.
Colocasia 'Black Magic'

Colocasia 'Black Magic'
Not this year.  'Black Magic' is a notoriously difficult colocasia to overwinter in cooler climates unless you have a well heated greenhouse or conservatory and can keep it actively growing all winter.  Unlike colocasias derived from the edible forms of Colocasia esculenta it is not adapted to dry storage.  I don't have heated glass so it has to take its chances in the house.  I withhold water to let it dry out a little and then keep it cool to trigger semi dormancy in the fleshy corms.  They don't appreciate going completely dormant or being too wet during the cool winter rest.  Grown too warm in the drier atmosphere of a house and the leaves can also far too easily get red spider mite infestations.  Getting the balance right is difficult but I manage it most years.  Even so, as a precaution I detach some of the small offsets and grow them on in warmer conditions in a well lit propagator. 

Last winter was one of my failing years for the main corms.  Conditions were a little too wet for them and they rotted.  No matter, I had a number of small offsets which, in a normal summer, would easily grow to a good size by August.

In a normal year, that is.

This summer has been anything but normal.  We've had a few warm days but not enough to trigger the explosive growth that abundant light, warmth, water and feeding can induce.  This is as far as they've got this year.

Colocasia 'Black Magic'
Barely a foot / 30cm high, small leaves and still in a 5in / 12cm pot rather than the 12in / 30cm containers they'd normally have been in by this time.  Not exactly the sub tropical feature that I look forward to every year.  In fact they'll probably be small enough to go back in the same propagator they came out of back in late March.

As always click on any of the pictures to enlarge.  In the last shot - taken today - you can see some little streaks in the top of the photo.  Yes, it's raining again.

1 comment:

  1. If it's any consolation, my Black Magic have been equally poor this year.

    During the few hot spells that we have had, you could really notice the improvement in growth, but overall, it has not been a good year for them.