Nitrogen affects several processes in plants and accurate detection of plant N status can help farm managers make appropriate N management decisions. An experiment was conducted under outdoor pot-culture conditions to determine the effects of nitrogen deficiency on castor growth, physiology, and leaf hyperspectral reflectance properties. Castor, cv. Hale, was seeded in 12-L pots filled with fine sand and were irrigated with half-strength Hoagland’s nutrient solution from emergence to 34 days after sowing (DAS). Thereafter, the following treatments were initiated: (1) control (100% N) continued receiving the half-strength nutrient solution; (2) reduced N to 20% of the control (20% N); and (3) withheld N from the solution (0% N). Photosynthetic rate, photosynthetic pigments, N concentrations, and hyperspectral reflectance of the uppermost, fully expanded leaves were determined at 3 to 4-day interval from 34 to 64 DAS. Based on stem lengths, leaf numbers and leaf length measurements growth and developmental rates were calculated. At 64 DAS, dry weights of various plant components were measured. Leaf and stem growth rates were more sensitive to leaf N than photosynthesis and leaf addition rates. Among plant dry weight components, leaf dry weight had the greatest and root dry weight had the smallest decrease under N-deficiency. N deficiency stress increased leaf reflectance at 555 (R₅₅₅) and 715 nm (R₇₁₅) and caused a red-edge shift to shorter wave lengths. Leaf N, chlorophyll and carotenoid contents were correlated with first derivatives of reflectance (dR/dλ) and reflectance ratios. Reflectance ratios, however, enhanced the prediction capabilities of photosynthetic pigments and leaf N content than single wavebands. The N-specific wavebands and the functional relationships between leaf N and growth and developmental processes would be useful for rapid and non-destructive estimation of leaf pigments in castor.