Trees are key roughness elements in urban environments, influencing airflow, microclimates, and pollutant dispersion. While aerodynamic drag is central to these processes, its behavior for complex tree-like structures at high Reynolds numbers remains poorly characterized. Here, we construct an analytical branch-wise drag model for fractal trees, validate it using lattice Boltzmann simulation results, and then use it to quantify the drag coefficient over a wide range of tree-height-based Reynolds number, ReH =U∞H/ν. The analytical model represents a fractal tree as an assembly of cylindrical segments; the drag on each segment is evaluated using empirical relationships and the total drag is obtained by summing contributions across all segments. Lattice Boltzmann simulations with adaptive mesh refinement provide reference drag data for L-system trees with iterations n = 4,6, and 8 (larger n generates more complex trees) over 2.5 × 10^3 ≤ ReH ≤ 1.2×10^5. Comparison with the LBM results shows that, although absolute values can exhibit systematic offsets, the analytical model reproduces the observed ReH- and n-dependent trends of the drag coefficients, supporting its use to estimate tree-scale drag at ReH higher than those simulated. The validated analytical model is then applied up to ReH ∼ 10^9. To the best of our knowledge, this provides the first quantitative prediction of drag crisis for fractal-tree geometries: a drag crisis is predicted near ReH ≈ 3×10^6 for every n (n = 4,6,8). As n increases, the transition becomes gentler because many small-diameter segments remain subcritical, which can reverse drag ordering across ReH. Thus reducing structural complexity does not necessarily lower drag; pruning can even increase drag under certain strong-wind conditions, motivating a reassessment of aerodynamic consequences in urban tree management.