Hashmaps vs storing data in the tree

I was working on my kd-tree and one of the changes I made was to store the data in the tree rather than in a hashmap, thinking that this would save time. However, in my benchmarks, it is much faster to use a hashmap. Does anyone know why this would be the case?

It's very strange question because hashmap and kd tree is absolutly different structures with different aims and contract and for sure map faster because it's nature. May be you publish source code with usage of map and tree?