Plants vs. Concrete... A Battle or Balance?

[atreis]

... I know that a lot of people use Quikrete cement for 3D backgrounds, so at least it's not uncharted territory. I've been looking at the ingredients, and I don't see anything "harmful" per say, and no heavy metals at all. Alumina, which is made from Bauxite and used in aluminum metallurgy is the closest to metal in the mix. It's commonly used in production of ceramics, so nothing too out of the ordinary. Silica is in there too, but it's also in sand, which is commonly used as a substrate. Basically I don't think anything will leach out that is harmful aside from increased carbonate hardness and therefore an elevated pH.

Silica is fine (that's just sand). Alumina would worry me... Aluminum leaching into the water could be bad. Don't know how much would actually leach though.

I like the idea of sealing it with 2 part epoxy, then you don't have to worry.

 

[plantbrain]

Gunnite or/and coating it is wise.
I've seen some very nice work, mostly from folks that were good with model trains and other small landscaping models already.

 

[SnakeIce]

Any time the hardness is increased there is reduced availability of nutrients unless nutrient concentrations are increased proportional to the increase of hardness. I had problems growing plants in the liquid rock water I had in Utah until I started dosing nutrients at higher levels. If I remember correctly calcium and magnesium, which are components of hard water, are negative cations and in high concentrations make other negative cations harder to obtain. So you may have to increase your other nutrient levels to compensate for the leaching concrete.

Or just coat it with something and be done with it.

 

[ZorroNet]

Or just coat it with something and be done with it.

A science lesson and a solution that doesn't require it... I like it!

 

[Pinkey]

I have no experience but could offer plenty of uneducated guesses. Instead I think I'll just request photos. How is it coming?