Kasama is located about an hour's drive north of Tsukuba and is well worth the trip anytime of the year. It is famous for its pottery, so you can enjoy the pottery theme park just to the east of Kasama while you are there.
The best way to go by car is to go over the mountain ridge to Yasato, along what is called the "Fruit Line" Road, running along the east side of the ridge of mountains just north of Mount Tsukuba. You'll come to another mountain pass to go over on what has now become route 42, which drops down into Kasama. That road dead-ends just after crossing the railroad tracks just to the east of Kasama Station. Turn right and go a few hundred meters to the end of that road. Turning to the right and proceeding east for a kilometer or so will bring you to the "Geijutsu no Mori" Pottery Park (on the left), while turning to the left and proceeding north for about 1km will take you to the park (on the right) where the chrysanthemums are.