Bulb food
Rodger Whitlock (Wed, 21 Oct 2015 12:42:38 PDT)

On 21 Oct 2015, at 16:01, Hans Huizing wrote:

I also use Pumice.
For the more difficult Cyrtanthus species I use pure Pumice 2-5 mm.
The root system develops very well in this material.

A demonstration that plant roots need air too. And I don't mean just epiphytes.

Since this material contains no nutrients...

Pumice (volcanic pumice) is nutrient-rich like other volcanic ejecta. Think
about the slopes of Mt. Vesuvius, which have been farmed for millenia because
the soil (decomposed ejecta) is so rich. Particularly rich in potassium, I
understand. The best part is that the nutrients in pumice are released slowly.
--
Rodger Whitlock
Victoria, British Columbia, Canada
Z. 7-8, cool Mediterranean climate