I have never had much luck with growing sweet peas - especially in planters. But this year I seem to have managed to grow them not only in the ground, but also in planters by my front door. I give the credit to this wonderful milky liquid.... that's right - rice water! An old lady once came to the door trying to sell me indoor plants and when I told her that I manage to kill all my indoor plants she suggested watering my plants with the water used to wash the rice each night. Of course I did my usual bowing and nodding and didn't think too much of it....until I tried it and I don't know if it is just coincidence or if it really does work, but my inside and outside plants in pots are all thriving. Worth a try - especially as it doesn't cost anything!