I have a number of Agave plants in the garden. I was in a homewares store and they had large clear glass vases with clean water in them and Agave plants growing in them. They were quite stunning and you could see masses of white roots in the bottom of the vases. I wanted to try this but when I dug up a plant from the garden the roots (except for an occasional one) were an unattractive blackish color. Can I chop off all the root section, place it in the clean water in the clear vase will it then grow new white roots as I saw in the store? Your advice would be appreciated.
I don't advise moving the agave plants from the garden soil to a water vase, and especially not to cut off the roots and hope they regrow.
Growing certain species of agave with hydoponic methods and materials may be possible, but I would recommend starting with plants that have been propagated for that purpose, not your garden transplants.
The homewares display is a showpiece curiosity and not conducive to long term plant health.
The blackening on the roots is representative of healthy humates and fungal associations that are vital for absorption of nutrients and protection from soil borne plant pathogens.