Any mulch will control weeds if the mulch is thick enough. Try the same experiment with damp newspaper, cardboard, grass clippings, straw, or what-have-you. If light cannot reach the weeds, they cannot grow. If they do grow, the mulch softens the soil so the weed seedlings are easy to pull up.

cyprus and eucalyptus are both ground up and can be used as a medium for hydroponic growing. i have never used either on in my hydroponic experaments but you might try the hydroponics forum on GW im sure someone over there can tell you about it. ~Ryan

Here is a link that might be useful: my hydroponics website

The State of TN extension service puts out a good booklet on mulches, their properties, uses, I think PH and whether they blow around, etc. Try your local extension service, or the web for booklets for state extension services. Good luck, Lotta

The information about mulches is in an FAQ at the weeds forum, I hope it's useful to your daughter.

Trudi Davidoff

Here is a link that might be useful: Organic Weed Controls ~ Mulches