I grew some corn plants from seed that is suitable for the Pacific Northwest. They germinated well, and some are forming ears, but I’m concerned that the stalks and tassels are turning purple. These aren’t purple corn varieties. Could it be a nutrient deficiency?
Since your plants are not naturally meant to produce purple corn, there is a good chance that the cause of the coloration is cultural or environmental. The Cooperative Extension website describes a number of factors that can cause the stalks to turn purple. Here is an excerpt:
“[Purple coloration may be caused by] cool temperatures, soil that is too wet or too dry, compacted soil, herbicide damage, insect damage, and root pruning by side-dressing knives or cultivators. Acidic soil can also intensify phosphorus deficiency symptoms. Low soil pH severely limits phosphorus availability to plants, which may cause deficiency symptoms even where high soil test phosphorus levels exist. Soil pH less than 5.5 typically reduces the availability of phosphorus in the soil solution by 30 percent or more. Acidic soil also reduces root growth, which is critical to phosphorus uptake.”
Before amending your soil in any way (such as adding phosphorus) you should have the soil tested.