Weeds, often considered a “menace” are top-notch, adroit survivors having intrinsic value as source of biodiversity and various promising uses as bio-resource. Among other benefits, their use as feed/food source or raw material is still to be explored. Weedy rice (Oryza sativa f. spontanea) a conspecific of rice has rapid growth, ability to uptake more fertilizer and produce large biomass. Lot of efforts are done for its management but little is known about its nutritive value and utilization as feed source for livestock. Therefore, the present study was carried out at Agronomic Research Area, University of Agriculture, Faisalabad in 2017 and 2018 to optimize N level and harvesting time for improving growth and silage quality of weedy rice sown as sole crop. Treatments comprised of four N levels viz: 0, 100, 120 and 140 kg ha-1 and harvesting intervals viz. 15, 25 and 35 days after heading (DAH). Weedy rice harvested at different intervals after onset of heading stage was used for making silage and analysed for nutritive value. Results depicted that, maximum plant height, fertile tillers, panicle length, kernels per panicle and LA were obtained with 120 kg ha-1 N and harvesting at 25 DAH during both years, while NDF, ADF, cellulose, and hemicellulose were highest with no fertilizer. Crude protein was highest with N application at 120 kg ha-1 and harvesting at 25 DAH. Highest nitrogen contents in plants, plant biomass, WSC, ash and DM in silage were recorded with 140 kg ha-1 N when harvested at 35 DAH. Weedy rice harvested at 25 DAH with N application at 120 kg ha-1 seems to be better combination for rational use of nutrients, better productivity and improving most of the nutritive traits of whole crop weedy rice silage.