This park has a very beautiful flower display which you can view in early May. The photos here were taken on May 1st 2008.
I don't recommend going here as a dedicated trip. However, if you are going to somewhere nearby (like Motegi or Mashiko) then you should stop here. It won't take very long to look around. Its a fairly small simple park.
There is a dam right next door to it which you can walk around too.
As usual in Japan you should plan to get here as early as you can so you beat the crowds.