Silt is like sand and clay but finer. You normally get it at river banks. I have it at the bottom of my garden, where the clay soil and fine sand from my garden washes down. It is feels like soft sand, glistens in the sun and has all the minerals from my garden mixed in it - so weeds grow well in it. Where you would buy it from I am not sure. You may be able to get some from a nearby river.

I collected some from my garden to root cuttings. TBH the results where not good and it smells a bit like a swamp when drying out. An alternative would be to buy horticulutral sand (fine grains) and mix that with clay soil.

thank you

Belladonnas are very strong and don't require anything special. Mine are planted with their noses at ground level in ordinary soil, and they grow alongside the highways here. What they need most is plenty of sun and a dry spell just before they flower in the fall. Then there is foliage until early summer when they die back. They won't tolerate freezing temperatures.

They do need good drainage, especially in a wet-summer areas like Georgia. If you have clay soil, I would replace the top 6 inches with a mixture of sand and compost, in an area 2 ft. across. Be sure to scratch in the first 1/2 inch or so of the mixture that you put into the bed, to make a transition layer--any sudden change in soil texture will stop drainage. Be sure to leave the top of the bulb exposed, too. I've heard that Nerines often work better in the South than Amaryllis belladonna.