Long Term Potting Mix Recipe - Alternative to Gritty Mix
I'm a new gardener from Perth, Western Australia whose been lurking on these forums for about a year now. I'm mostly interested in containerised edible gardening. I thought I'd share a recipe for a long term potting mix that I found recently.
I bought quite a few (probably a few too many) dwarf and semi-dwarf fruit trees last year which I put into smaller pots. I'm now ready to repot them in larger containers: some ~50cm diameter glazed ceramic pots and some half wine barrel planters.
But this raises the question - what's the best potting medium for long term use? I've had a look through some threads which outline Al Tapla's Gritty mix but tracking down the ingredients locally is difficult. Also given Perth's Mediterranean climate (hot dry summers, cool wet winters - USDA 10a) and water restrictions during summer which allow reticulation only twice a week I wonder if the gritty mix can hold enough water. I know myself well enough to know I won't regularly hand water.
I found an alternative suggested by local Perth horticultural consultant Peter Coppin. He has three short youtube videos. The first is on the size & type of pots (http://www.youtube.com/watch?v=Whp1Kh4R5zw), the second is about the soil/potting mix (http://www.youtube.com/watch?v=zzPc5DJuGJc) and the third shows planting & establishment of the new trees (http://www.youtube.com/watch?v=9XvmTLO_h9I)
Peter's potting mix -All parts are by volume (not wieght)
1 part good quality potting mix for organic matter
1 part course sand (e.g. washed river sand, quartz sand, lawn blend) for drainage
2-5kg Bentonite clay per 100L (sodium or calcium bentonite) for water retention
Suggested Additives - per 100L Basic Mix
100-200g Low nitrogen rock dust
600g Zeolite (holds moisture and nutrients)
1 part Perlite/Vermiculite per 4 parts basic mix to reduce weight
Expanded clay - fill bottom of pot 1 or 2 clay balls deep to hold water
Peter says that this mix should last 10 years if you use a half winebarrel sized container (100L). He suggests hiring a cement mixer to evenly mix all the ingedients. In Australia all the ingredients are redily available. You can buy clumping kitty litter which made from sodium bentonite from Coles. Zeolite you can get from Bunnings as Zeo-Chlor pool filter replacement. Peter uses Ecoprime Natural PK rock dust.
I'd be interested to get everyone's thoughts on this mix or if you've used something similar before. Also how it stacks up to the gritty mix.
Here is a link that might be useful: Peter Coppins Website
This post was edited by arcan on Thu, Aug 14, 14 at 21:46