I’ve noticed that a number of my plants have yellow lower leaves (bee balm, phlox, spiderwort). Might this be a result of the wet spring or something else? Soil is very sandy ( I’m in East York) but I’ve been amending it for years. The site gets lots of sun. I’ve also had lots of mushrooms this year. Thanks!
Yellowing leaves can be a sign of a number of different issues, but frequently are the result of moisture stress – either too little or too much water. Given our wet spring, it is very likely, as you’ve suggested, that too much water is causing lower leaves to yellow. The abundance of mushrooms is another clue that too much moisture is to blame.
Since we can’t change the weather, the best you can do is to closely monitor your soil moisture levels, and avoid any additional over-watering. You mentioned your soil is sandy and that you regularly add amendments, so drainage is likely not the problem. However, you may want to test your drainage by digging a small 6 to 8 inch deep hole (be careful not to damage any nearby roots!), and fill it with water. If it takes longer than a hour to drain, then you may have a drainage issue.
During wet weather there are a few practices that can help keep your plants as healthy as possible. Avoid walking in your beds when the soil is damp to reduce soil compaction which can further stress waterlogged roots. Monitor your garden closely for evidence of fungal diseases, such as powdery mildew or anthracnose, and remove infected foliage quickly to reduce further spread. Periods of heavy rain can leach nutrients from the soil, so routine amendments with organic materials is a great preventative measure. Monitor your plants for signs of nutrient deficiencies, particularly nitrogen which is easily leached. Nitrogen deficient plants are often display spindling growth, with foliage and stems that are yellowish or lighter green than normal. The Toronto Master Gardener’s guide to organic fertilizers is a useful resource for addressing the nutrient needs of your plants.