Eco-friendly recycling and waste management strategies are increasingly becoming important in reducing soil and air pollution, greenhouse gas emissions, ecosystem imbalance, and degradation of biodiversity. Nanotechnology is a long-term waste conversion solution that enables efficient degradation of pollutants, heavy metal adsorption, and resource recovery. The waste flower is an excellent bioresource with high contents of phytochemicals, including flavonoids and polyphenols, which can be used as natural reducing, capping, and stabilizing agents in the green synthesis of nanomaterials. A few of the advantages of this method compared to traditional chemical synthesis include increased stability of the nanoparticles, biocompatibility, and reduced toxic byproducts. Photocatalysis, water treatment, and biomedical photocatalysis green-synthesized metal and metal oxide nanoparticles have been used in photocatalysis, water treatment, and biomedical applications. Their multifunctionality is confirmed by structural and functional characterization. Such nanomaterials can also be used in the field of sustainable agriculture as nanofertilizers and environmentally friendly pesticides. It is economical, energy-efficient, and industrially scalable to use floral waste. By converting trash into useful goods for the benefit of the environment and society, it may progress the objectives of the circular economy with further safety studies and laws.