Kim Rupert on preventing molds on rootings and seedlings
My houseplants indoor didn't do well last winter: mold and black canker, white flies, etc. The indoor plants grown in MiracleGro potting soil retained too much moisture, so I asked Kim Rupert as to what's the best soil to prevent molds.
Kim is the breeder and rosarian in California who advised the "burrito wrap" method to create calluses for better rooting. He advised NOT TO COVER rootings in a damp climate to prevent molding. Here are some questions I asked Kim and his answers:
Straw: "I see your cuttings do really well in Styrofoam coffee cups, how do you prepare the soil to prevent molding?"
Kim Rupert: "I only use bagged potting soil with lots of holes in the cup bottoms. I stack several cups then push a pencil through their bottoms in several places. As long as your potting soil is fresh, not previously planted, and there are enough drain holes, it doesn't mold. "
Straw: "Some folks said to microwave the soil, but I already bought a seed tray with tiny cells."
Kim Rupert: "In those tiny cells, I'd use a seed starter mix like this. (See the link below)
You want it to drain quickly, retain moisture, remain light and friable so small seedlings can push up through it without damaging them. Since you'll be watering inside that bath room tub, it doesn't have to stay as wet as it would need to outside where it's hot and dry (here). If your water inside is softened, you don't want to use it as they need the minerals and can't tolerate any sodium softeners can add.
If you raise them outside after the last chances of hard, killing frost, you won't have to worry about rotting or damping off. Use a well draining but moisture-retaining with at least a third coarse sand mixed in, then cover the surface with about a quarter to half inch of perlite. Wind can blow it away, so something with deep sides like the box we discussed could be used. "
In one of the thread on rooting, Kim advised planting cuttings deep in the soil, leaving only 1" to 2" above ground. Kim wrote: "As long as you experience higher relative humidity, covering your cuttings with plastic or glass is going to pretty much guaranty they'll rot. If you're having those issues, try planting them deeply so at least half (or more if possible) of the cuttings are under the soil level. That should help without the mold issues."
Here is a link that might be useful: Organic Soil mix that Kim Recommended