I earlier bought a
pot which had already had seeds planted in it and I just had to water it everyday and wait for the grass to sprout. It was really easy. When Angel finished chomping or rather chewed off the nice green grass, I threw the pot (made of thick hard paper) without thinking. I could have reused it and the unusual soil to hold new seeds.
Anyway, I bought a packet of pet grass seeds from Sundreams, the pet shop @ Far East Shopping Centre. I can't remember the exact price but both the seeds and the pot cost around the same. I figure that it's more worthwhile to get the seeds and plant them myself instead of buying another pot.
It was also easy for seeds I planted in the milk carton to grow.

Angel enjoyed eating them. Angel has the funniest expression sometimes :)
