Lava Rock makes an excellent addition to bonsai soil substrate as it retains water but doesn't allow bonsai tree roots to grow into it. Lava rock is a solidified molten igneous rock that has flowed from volcanic eruptions.
Lava rock also makes an excellent top dressing and can also be used in a humidity tray.
Features of Black Lava Rock:
Provides excellent aeration which provides oxygen to the roots of the bonsai tree
Has water-retention properties which supplies moisture to your bonsai tree between each watering
Allows excess water to drain quickly from the pot which prevents water salt build up and root rot
Known to help with strong root regeneration, especially with newly collected trees
Substrate particles are mostly 1/8-1/4" with some variation
Purchase one bag of lava rock for $8.99 or purchase three bags for $23.99 and save $1 per bag
Quantity per bag: 1.5 lbs is approximately 3 cups of black lava rock