(1) The focus on floral functional traits and their variability has been significantly lower than when compared to other plant organs. Here, we focused on the variability of four novel floral chemical traits. We aimed to assess the level of interspecific variability of total non-structural carbohydrates (TNC) and total phenolic compounds (TPh) in the flowers of woody species. (2) We collected data on 70 species of temperate trees and shrubs. We also assessed the intraspecific level of variability by collecting flowers from the high-light and low-light parts of the crown. (3) We found a phylogenetic signal in the variability of starch and TPh. We did not observe statistically significant differences or biologically significant trends between the high-light and low-light parts of the crown. We detected a low impact of light availability on the intraspecimen variability of the TNC and TPh contents. (4) Low intraspecimen variability allows for a more reliable extrapolation of measurements in cases of interspecific comparisons and can be used to better describe the reproductive strategies of different woody species.