Petunia leaves in windowboxes and in raised beds have yellowing leaves, some have even shriveled up and died. I water windowboxes every other day; water raised beds deeply once a week. Marigolds have shriveled up & are dying. Geranium leaves are yellowing. Don't understand what's happening. What do I need to do?

sounds like you may be overwatering. Don't water on a schedule, water when you've put your finger into the soil and it feels dry.

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Sandi
Texas Certified Nursery Professional
Texas Master Naturalist
Organic gardener
Tree-Hugger
Native Texan