Marigold Has Blackened Leaves And May Be Planted Too Close To Cosmos

Question From: Vilnius, Vilnius County, Lithuania
Q: is my marigold too close to my cosmos? they are only about 4 inches across. the marigold has blackened leaves as if they were sizzled by fire. still looking for the cause and cure. can you help?

A: Spacing plants too close together cuts off the circulation of air prevents wet leaves from drying after watering or a rain. That's the perfect setting for fungal diseases develop and spread, which turns the leaves black. I'd pull the plants and clean up all the dead material. Watering flowers at soil level will help keep the leaves dry. Your might try using a fungicide. I like a produce called Serenade. It contains a bio-- remedy called Bacillus subtillis and is OMRI listed. Over fertilizing also encourages disease so add compost when planting and watch your flowers thrive. Best And Happy Yardening, Nancy