Water hyacinth (Pontederia crassipes (Mart.) Solms) (Pontederiaceae) is one of the invasive aquatic plants native to South America that has become a significant environmental and socio-economic concern in Ethiopia‘s Lake Tana. Its uncontrolled proliferation threatens social, ecological, and economic issues. The current study was made to assess the spatio-temporal water hyacinth (WH) populations dynamics and explore its sustainable utilization through vermicomposting in order to mitigate its impact and enhance agronomic productivity. Field surveys were held during March 2023 to January 2024 at four purposely selected sites (Tana Kirkos Monastery, Firka Dangurie, Sheha Gomengie, and Lemba Arbaytu). Sampling was made at three 0.5 m × 0.5 m quadrats in order to bimonthly monitor growth patterns and biomass accumulation. The peak coverage of WH occurred in September (913 hectares), while the lowest coverage was recorded in February (461 hectares). WH biomass significantly (p<0.05) reached peak in November at 45.33 kg/m² (500 t/ha) at Tana Kirkos, with the shoot system comprising 67.5% of the total biomass. Nutrient analysis significantly (p<0.05) revealed water temperatures of 21.0°C, a pH of 7.07, and dissolved oxygen levels of 5.11 mg/L. To evaluate the potential of WH biomass for agronomic use, vermicomposting was conducted using mixtures of WH and cow manure (2:1, w/w) with 7.5% charcoal (T1), 5% charcoal (T2), and no charcoal (T3) supplementation. Over 90 days, T1 and T2 significantly (p<0.05) enhanced earthworm growth, survival, and reproduction compared to T3. Vermicompost from these treatments significantly (p<0.05) increased pH (4.30–5.75%), total nitrogen (53.6– 62.5%), phosphorus (61.6–117%), potassium (47.5–71.3%), and vermicompost mass yield (22.0– 28.3%) over T3. Additionally, lettuce seed germination and growth were improved, with germination rates of 92.4–93.5% in T1 and T2. An open-field experiment was held to assess the suitability of WH-derived vermicompost as a partial substitute for conventional nitrogen, phosphorous, and potassium (NPS) (19N-38P₂O₅-7S) fertilizer in lettuce cultivation. Treatments included recommended NPS fertilizer (F1), 2.5 t/ha vermicompost (F2), 5 t/ha vermicompost (F3), 2.5 t/ha vermicompost + 50% NPS (F4), 5 t/ha vermicompost + 50% NPS (F5), and unfertilized control (F6). The F4 treatment significantly (p < 0.05) resulted in the highest fresh weight (215– 227%), vitamin C content (82.1–94.8%), marginal rate of return (157%), and reduced aphid populations (52.8–86.6%) compared to the control (F6). Soil quality indicators such as pH, electrical conductivity, and nutrient content were also improved in F4 and F5 treatments. A greenhouse experiment investigated the potential of substituting cocopeat with WH-derived vermicompost for seedling growth. Substitution levels were WH vermicompost [0% (T1, control), 10% (T2), 20% (T3), 30% (T4), 40% (T5), 50% (T6), and 100% (v/v) (T7)] under greenhouse conditions based on a completely randomized design (CRD) with three replications. T2-T4 significantly (p<0.05) improved seedling emergence (> 90%) for both lettuce and, tomatoes, increased seedling height of lettuce (20.0-21.7 cm) and tomato (20.0-22.0 cm). Also, seedlings grown in T4-T7 suffered significantly (p<0.05) less from leaf-damaging pests. However, higher substitution levels (T5–T7) led to reduced total porosity and water-holding capacity, indicating the need for optimal substitution levels to balance growth and media properties. Findings in this study