People have asked and here it is my Figfather big box store soil recipe:
1- 25 quart bag of miracle gro moisture control potting mix
1- 1 cubic foot bag of miracle gro cactus, palm & citrus soil
2- 8 quart bags of miracle gro perlite
2- 40 pound bags of mushroom compost.
Do not use other types of compost it has to be mushroom compost. Using animal compost is not advised and can do more harm than good.
Step 1.) Mix the mushroom compost and the perlite together first.
Step 2.) Then add in the rest and mix well.
Perlite - aerates providing oxygen space to roots when you water.
Mushroom - compost feeds and helps with soil not drying out so fast in sunny summer days.
Moisture control potting mix - helps with over and under watering along with keeping things lite.
Cactus, palm & citrus soil - helps with drainage.
Adding an inch of crushed rocks to the bottom on the pot also helps allot. Nothing special the stuff they put down before the pour concrete over it is just fine. The courser it is the better. Rocks are minerals which plants love and also help with drainage. Please keep it no more than 1 inch. There is a fine line between too much being harmful to drainage and to little not doing anything. 1 inch give or take a 1/4 inch is plenty.
When adding a mulching layer for year one I tend to go for a bag of Cypress mulch over the pine bark mulch. Figs come from the Mediterranean and there is allot more fallen Cypress in that area of the world. My general thought process is that a fig in the wild is more likely to have a fallen Cypress tree mulch the ground around it than a pine tree. Maybe I’m over thinking it but at the store by me they are the same price so Cypress is the way I personally go. After year one I use the figs fallen leaves and unripe fruits as the mulching layer as it slowly builds over time year after year.
Be sure to have extra soil mixed up for the following couple years. As with all potting soil; year after year you will experience shrinkage and this is mainly to do with most potting mixes using peat moss or coco coir. Completely normal for root ball to compress and shrink a bit each season so adding a bit more soil each year to top it off if needed is helpful. Just remove the mulching layer and fill it in and top it off then add back the mulching layer. Shrinkage occurs the most between year 1-3. Keeping your root zone consistently moistened prevents the media from overly shrinking and becoming hydrophobic to water. If your root ball has dried out simply shower it with a little bit of eater, wait 5 minutes then come back and repeat. Doing that a few times will plump up your soil again to where it holds the water vs just having the water shed off it and with it take your top dressing / nutrition with it.
Also add a top dressing on top each year! Aside from regular liquid fertilization adding the top dressing at the beginning of each season to your pots is big. Just move your mulching layer away and add it in. Then just move your mulching layer back on top. Container grown figs need to be fed well or you may suffer growth, fruit, and vigor performance to decline season after season. I do not mix my top dressing into my soil. All my amendments to the soil mix lay on top so when you water they trickle down through the rootball vs being mixed in. I highly recommend top dressing only.