The Lefkovitch stage specific matrix population models are divided into discrete stage classes defined by a growth variable such as size, height and diameter at breast height for trees. In matrix model, the deterministic matrix projection models are used to estimate growth rate, stable size distribution, reproductive values, and sensitivities of the growth rate to changes in vital rates. This study sampled five forest blocks (Kiptogot, Kimothon, Suam, Saboti and Kitale within Mt. Elgon forest ecosystem) and used stage base matrix models to estimate asymptotic growth rate, sensitivity and elasticity values of invasive tree population within the forest ecosystem. The result concludes that the dominant eigenvalue is more sensitive to transition probabilities from stage 2 (sapling) to stage 3 (Mature trees) stages of Cestrum aurantiacum than to transition probability of stage 1 (seedling) to stage 2 (sapling) and lower in fertility of the stage 3 (Mature trees). The results further shows that the growth parameters in the forest blocks shows that Kiptogot block had the largest elasticity values than the other blocks, indicating that the invasive tree growth survival probabilities had greatest impact on population growth.