Functional-Structural Plant Modelling (FSPM) is plant modeling that considers morphology, physiology, and statistical data. One of the software for FSPM is the Growth-Grammar Interactive Modelling Platform (GroIMP). GroIMP is a Java-based platform using the XL language, which is a language developed from System-L. This study aims to build a virtual plant model of green amaranth (Amaranthus Sp.) in a hydroponic planting system for strategic decision-making. In this study, parameter analysis and

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... odel development were carried out. The model is divided into two submodel blocks by operating three methods. There are two sub-models, namely the sub-model virtual plant, and the sub-model fuzzy logic. In the virtual plant model using mathematical modeling and FSPM-GroIMP methods, the results of this model are the growth pattern of green amaranth to harvest, the weight of green amaranth, and visualization of hydroponic green amaranth plants. In comparison, the sub-model fuzzy logic uses the fuzzy logic method to predict the selling price of plants and expenses. The two sub-models are combined to produce hydroponic green amaranth strategic decisions. The output of strategic decisions is a decision that has an impact on investment value. The investment value is measured by the CR Ratio, which is the investment value by comparing the cost with the revenue from hydroponic green amaranth. Other results showed that the average weight of a single green amaranth plant is 11.85 g and the RC ratio value is 4.5 for 500 plants with good plant quality, a fixed cost of IDR30,000, variable cost is IDR20,000 and the price is IDR57,282 per kilogram. Calculations of model verification and validation were carried out and indicated the built model according to the existing theory had the correct variable values.