Milk has been used as a fertilizer for long times. The "extra" calcium provided by milk could account for this growth that you see. Plants use calcium for growth. A lack of calcium is indicated when a plant's growth looks stunted. Milk is also used as a pesticide and as a fungicide.

I will continue doing this over some time and let you guys know the results.

Good thing is that there is another cutting which was taken from same tree and which gets watered via drip system everyday during summers. Though the amount of sun they get is a different still should make an intresting study.

To test your hypothesis you'd need to do exactly the same regime to another hibiscus in the same position using milk bottles which have no milk at all left in them. Then you'd be comparing the milk-water with an identical quantity of plain water. Comparing with a tree on drip wouldn't be the same.

Ps I do hope you're taking those bottles to the recycling bin and not the 'garbage' bin ;-)

I'm thinking it's just as likely to be the nitrogen in the milk protein as it is calcium. But who knows. As long as it works!

@floral: Yep recycling bin.

Hmm...... Comparision will be flawed I guess. Anyways. Will still see how it works out.