Water spinach (Ipomoea aquatica) is classified as a noxious weed by the USDA. However, it remains a popular vegetable in Southeast Asia. Water spinach thrives in warm, moist conditions. Demand for water spinach is increasing in the state of Georgia. The present study assesses the effects of planting date and organic fertilization rate on water spinach yield. The study was conducted in an organically certified high tunnel at the University of Georgia Tifton Campus. Organic fertilizer was applied and incorporated into the soil before planting. Water spinach seedlings were grown in a greenhouse. Within the high tunnel, plants were cultivated on drip-irrigated raised beds (1.8 m apart center to center), covered with white-on-black film mulch. Plants were grown in two rows per bed, with 45 cm between rows and 30 cm between plants. The experimental design was a split-plot arrangement with three replications. The main plots consisted of three planting dates—T1 (16 May), T2 (9 July), and T3 (3 Oct.)—while the subplots included four fertilization rates: 0, 56, 112, and 224 kg/ha of nitrogen (N) applied as organic fertilizer. Plants (shoots) were harvested by cutting 5 cm above the soil surface: four times for T1, three times for T2, and once for T3, with the final harvest conducted on 22 Nov. Shoot fresh weights (FW) were recorded. Results showed that cumulative shoot FW was highest at the earliest planting date (T1; 2.77 kg/m²), followed by T2 (2.36 kg/m²), and lowest at the latest planting date (T3; 0.062 kg/m²). The reduced cumulative shoot fresh weight observed in the latest planting suggests that cooler fall conditions significantly limited plant growth. Regarding the fertilizer rate, the cumulative shoot FW was highest at the 224 kg/ha N fertilization rate (2.03 kg/m²) and lowest at 0 kg/ha N (1.41 kg/m²). However, the relatively high shoot growth at 0 kg/ha N is notable and may indicate the presence of confounding factors. Plants exhibited vigorous shoot and root development, including the formation of adventitious shoots, which likely allowed them to explore soil beyond the experimental plot boundaries (the separation between plots was 30 cm). Visually, plants appeared to grow more actively when provided with ample soil moisture and organic fertilizer. In conclusion, the optimal planting window for water spinach in South Georgia appears to be from April to July. The effect of fertilizer rate on water spinach growth could not be conclusively determined from this study.
