If you meant “Goldenrod’s surrounding routes,” there are 7 headbutt trees between Routes 35 and 36. But the Grand Hall itself has none.
The confusion likely stems from and Route 36 , which are directly north and south of Goldenrod City. These routes feature headbutt trees — special trees where using the move Headbutt causes wild Pokémon (like Heracross , Aipom , or Spearow ) to fall out. The Goldenrod area has several headbutt-able trees, but none inside the Grand Hall itself.
So where does the question come from?
Here’s a short, investigative-style write-up on the question: Investigating the Grand Hall’s Headbutt Trees In Pokémon Gold, Silver, Crystal , and their remakes ( HeartGold & SoulSilver ), the Grand Hall in Goldenrod City serves as the city’s connection hub for the Pokémon Communication Center (a feature originally tied to the Mobile Adapter in the Japanese versions). However, the area players typically refer to as the “Grand Hall” is a single indoor room with a desk, a PC, and a few NPCs — no trees at all.