Soil(SOIL): Powder. VINE and PLNT grows along it, WOOD will replace it slowly (every 150 frames it has a 30% of replacing any adjacent SOIL)
Bark(BARK): Looks and acts like wood (including replacing soil), but PLNT and VINE don't grow along it. Turns into WOOD at 50 °C. Useful for making trees.
1. Soil - Might be usefull. I suggested soil in my earlier work and my soil has more uses.
2. Bark - Has it more uses? You can use IGNC or Coal for trees.