The visit of the garden is well worth 50 rubles. And, contrary to other national parks and places where you wonder if they really need the money, here, it is obvious they need the money. It must cost a pile to keep building up their collection of empty alcohol bottles and buying the old steel bed frames, that are the main recurrent themes of the garden. Past the handful of bonzai trees that give the park its name, one can tour the main part which I guess is built around the theme of "post-war Nagazaki". There are a few signs saying :"Smile, you are on camera" are displayed prominently, just in case you had an impulse of steeling a cement bag or an old tire from the park.
So overall... if I were writing a guidebook I think I would give this park a nice little symbol that says:"to avoid". It is not better than on the other side of the fence, outside the park, where you don't have to pay to walk in the landfills.