The pictures above are the species commonly found growing in the wild in Singapore. The ones below found cultivated in a park back in 2011 may be a hybrid. It was much shorter than the wild version.
This plant below is commonly called Ma Cao (马草) or Mu Cao (牧草) among folks who are into herbal stuff for healthy living. Translated literally, it means "horse grass" or "domestic animal grass". The hype about this grass was on its health value, which according to what I have read seemed quite amazing. This grass variant or hybrid was concocted in Taiwan in 1996 and was designated a local Chinese name 狼尾草台畜草二号 (Napiergrass Taishigrass No. 2). The main distinction between the wild and this hybrid is the quantity of fine hairs on the plant. The hybrid is almost hairless.