Varietal and seasonal differences in oxalate content of spinach

Varietal differences in oxalate content were studied in our spinach collection. The oxalate content of 213 spinach varieties tested in the summer of 1997 ranged from 0.76 to 1.8% of fresh weight. Varieties with round blades generally contained less oxalate than those with lobate blades. Fifteen varieties were tested again in the four seasons of 1999, then these tests were compared to the two tests in 1997. The correlation between oxalate content in the summer and in autumn-to-winter was not significant at the 5% level. On the other hand, there was a positive correlation with 1% significance between any two of the four tests in the summer, and there was also a positive correlation with 5% significance between the two tests in the autumn and the winter. These results suggest that using one season of the year for cultivation is necessary to find higher or lower-oxalate spinach.