Tokorozawa Lily Garden comes to life every June, and it is currently in full bloom. The lilies fill the horizon and you can walk right into the field among the lilies. The bloom should stay till 1st week of July and worth the trek.
From Shinjuku station, take seibu Shinjuku line to Higashi-Murayama. Travel time is around 40 min. It is a 15-min walk from the station to the Lilly garden. Right next to the garden is also an amusement park (roller coasters) and baseball dome (Seibu Prince Dome).