3/4 Potting soil 1/4 sand for example. 1/2 potting soil 1/4 reg. dirt. 1/4 sand 1/2 old compost 1/4 reg. dirt 1/4 sand All potting soil. etc... Use soil without slow release ferts. No manures, no meals. Don't use cheap soil you buy (some have micro organisms that will kill the sprouts). Don't use outdoor native soil for inside (unless you cook it in the oven lol).