I noticed the grain size of soil garden does not have any ill effect on the bulbs. It is a bummer that most of the garden lies in a deep shade in the winter, when the sun is low behind trees, buildings and other construction. The end result is etiolation, and gladiolas are mostly affected because their stem does not stand well against the winter storms. Tulips do well in peat but I don't plant them because they need a much colder winter and the summer is just too hot. My experience shows they can't store enough nutrients and they divide into many tiny bulblets, losing mass overtime. My targeted plants are mainly South-African bulbs, comprising Gladiolus species (not including the hybrids in European gardens), Ixia, Massonia, Geissorhiza and Daubenya. I'm exploring the market for more species. Other bulbs grow in peat and I'm not concerned about finding the correct potting mix. These include Crocosmia, Watsonia, Homeria and Ledebouria. I'm also a member of the Cactus society, and the website has one recipe for cacti. Is that soil good for these bulbs? The soil make-up is: 1x dune sand or fine sand 1x perlite 3x peat 4x ground pumice 1x compost (This amount is for seed-starting, you can add more for mature plants) All five components are readily available.

Me too! I may not use a ton -- but when I want pumice, it's ALWAYS General Pumice Products I order from. Over the years, I have found the product CONSISTENT in size, low in dust. I no longer sift it, I just wash it and it's fine. I like perlite because it's light in weight -- BUT, living in FL, the humidity turns it a disgusting mustard color AND then it softens in the pot and breaks down, thereby defeating the purpose of porosity. I use pumice WITH SOIL, or with a gritty mix of Turface and Manna Pro....and I use pumice ALONE.

Could also be a)They are high in non organic minerals of their volcanic origin b) they have holes in them, alowing the plants roots to enter them c)They are very draining and dont retain moisture. Dont know if this is relevant, but we do have op. humifusa growing in this volcanic region, somewhat outside its invaise growing range.

I have no experience with that product but you might try this method which a friend of mine recently used to separate some chafe from seeds. Get a portable fan and a 5 gallon bucket set up in your backyard. Have the fan blowing towards the bucket and you stand behind it. Reach over the fan and pour a small amount of your product into the bucket so the fan can blow it away over the bucket. Good luck with your project and plants.