When I lived in the country and grew many kinds of bulbs in pots in unheated frames, I always made up my potting soil with coarse sand, pumice, and topsoil that I dug in my alder woodland and sieved. During potting season I started each day by preparing a large wheelbarrow of this mainly leafmold soil, which I then mixed with the other ingredients, which I was able to buy by the truckload. This introduced a wide range of microorganisms to the bulbs' soil. I always felt that this helped. Now I can't get natural topsoil (the soil in my new garden is heavy clay, which can't be mixed in) and the bulbs are not growing as well, even though I fertilize them adequately. I'm gradually changing the soil mix in my bulb beds to incorporate more pumice and organic matter, but it's impossible to buy organic soil components here that don't contain composted bark and/or sawdust (unless you choose straight manure), and I have always thought wood products are bad for summer-dormant bulbs. Jane McGary Portland, Oregon, USA On 2/4/2016 4:36 PM, Karl Church wrote: > Travis, > > As a Master Gardener, I've heard several speakers talk on need to protect > the microorganisms in the soil if you want excellent growth. So I suspect > you have a good idea regarding those bulbs that tend to be difficult to > grow outside their native location. It would be interesting if someone did > the research. >