Shamrock Plant (Oxalis regnellii) is an ornamental plant grown primarily for St. Patrick's Day. Interveinal chlorosis is a production problem and has been hypothesized to be caused by micronutrient deficiencies, either iron (Fe) or manganese (Mn) or virus. Several experiments were conducted testing these hypotheses. A virus screen was conducted and positive identification was found and plants were rouged. Oxalis plants were grown hydroponically on five NO3--N:NH4+-N ratio treatments. Increasing proportions of NO3--N increased total leaf, root, flower, and bottom shoot biomasses. Other hydroponic studies were conducted removing Fe and Mn from nutrient solutions to characterize the respective deficiencies. Iron deficiency, characteristic interveinal chlorosis on newly developed leaves was observed as early as three weeks after removing Fe. Plants grown without Mn did not exhibit interveinal chlorosis, but were slightly less green than control plants grown in complete nutrient solutions. Iron deficiency was also induced in a greenhouse media, using dolomitic lime. Again, typical interveinal chlorosis and reduced plant growth was observed after two weeks. Tissue analysis confirmed the chlorosis was due to reduced Fe as opposed to limited N or Mn concentrations. Our data suggest Fe influences interveinal chlorosis more than Mn. Micronutrient chelate foliar and media applications were assessed as corrective measures for foliar chlorosis. Media drenches of Fe-EDDHA were effective in regreening Fe deficient oxalis in 5 days. Foliar chelate applications were less effective. Organic acids, such as oxalic acid often assist plants in nutrient acquisition through root exudation. Oxalic acid levels of recently matured leaves increase in Fe deficient O. regnellii plants. Cultural practices such as temperature, irrigation, and fertilizer selection also influence plant growth and incidence of leaf chlorosis. Our research found that cooler temperatures (13˚ C) did not increase chlorosis and temperatures of at least 21˚ C produced more aesthetically pleasing and floriferous plants. Overhead irrigation, compared with subirrigation produced higher quality and larger O. regnellii. Plant growth and development is best when fertilized with N rates between 100 mg N[MIDDLE DOT] L-1 and 350 mg N[MIDDLE DOT] L-1.