This seems never to have appeared on aroid-l, so I’m resending
From: Peter Boyce [mailto:firstname.lastname@example.org]
Sent: Wednesday, 17 August, 2011 5:14 PM
To: 'Discussion of aroids'
Subject: potting mixes
For information for those of us (and that includes me…) who are not regular IAS Forum users, there has been a string on potting mixes running on the Forum for a while.
In advance of what I'll be (in part) presenting at Miami in September, I thought it would be maybe useful to post on what we use here in the wet tropics.
Here is a copy of what I posted on the Forum:
We use 2 parts black peat (pH ca 6), 1 part sieved red soil (Tarat series), pH 4.5, and 1.5 parts washed river sand (pH ca 6). For limestone-originated species we add 1.5 parts calcium or magnesium carbonate chips (ca 1 cm chips). Pots are shallow unglazed clay (terracotta) with one large basal hole and three large lateral holes. Pots are crocked to 2.5 cm depth with broken brick (2-4 cm pieces), or with equivalent in similar-sized limestone chips, as appropriate.
Our plant houses are all on tank-fed automatic misting set to come on for 2.5 minutes, 3 times an hour. Droplet size is large (ca 350 microns). Apart from an initial watering when re-potting we never direct water the soil, so soil compaction is kept to a minimum. Fertilizer (NPK 15:15:15+ microelements) is applied through the misting system once a month, with the fertilizer applied for a standard misting cycle for a period of 8 hours and then the system flushed.
We use three different shade/ventilation regimes. One house is arranged to provide 75% shade, <25% lateral ventilation, a max temp. of 30C and minimum humidity of 70% houses mainly rheophytes and species from gallery forest; another house has 50% shade and + 50% lateral ventilation, a max temp. of ca. 35C and a minimum humidity of 50% is used primarily for Homalomena; the third house is 50% shade with >80% lateral ventilation, giving a max. temp of 36C and a minimum humidity of 40%, is used for the larger, colonial Schismatoglottis, Amorphophallus, etc.