Red lava rocks

[John2468]

Hi, I read that red lava rocks are bad for plants as they contain high iron content, has anyone had problems with this? Thanks!

[Rivera]

I can't give you a complete answer John, but the presence of iron (even in high concentrations) does not necessarily indicate high bioavailability to your plants. 

I imagine highly acidic soil would increase Fe bioavailability, but I don't know this for a fact. I believe it's true that excess iron uptake can inhibit uptake of other nutrients (eg: essential micros like manganese). 

Some palms would favor high iron availability (eg: high plateau palms from Madagascar).

Personally, I wouldn't worry about it.

[Tomas]

The elements from the lava rock will be available to the plants as the rock decompose, so very slowly.

While Fe has many antagonists (elements that will make Fe not available to the plants, like for example Calcium), it itself is not antagonist to any element except Phosphorus 

I hope it helps

Tomas

https://www.nutriag.com/mulderschart/

[Urban Rainforest]

Whenever I plant a Cycad in the ground I dig my square planting hole then I dig a chimney drain in the bottom of the planting hole and backfill it with a 50/50 mix of red lava rock and sand. I do this to facilitate drainage in case of abnormal el nino type rains. I have never had any issues from the red lava rock and in fact have never lost a Cycad in the ground planting this way.

[Silas_Sancona]

Use red and black Lava quite often in potted soil mixes. Never once had any issues w/ it.. 

Plenty of examples of Orchids, various Bromeliads, Ferns, etc... happily grown on rip rap- sized chunks of lava as well..


Whatever internet source says " plants may have issues being grown in ..or on... the stuff " ..Black or Red..  obviously didn't research habitat photos/ info of plants growing on Lava ..naturally... in Hawaii, Mexico, the Caribbean  *< Where applicable* , and/ or other regions of the world where raw lava is all plants have to grow on right after / decades after  an eruption. 

Would be numerous areas here in AZ completely devoid of any  plants if they had trouble growing on it for sure.