You perhaps missed last summer’s plant plague, which might be back this summer. My garden was spared because last summer I happened not to have planted the particular host plant: impatiens (Impatiens walleriana), that workhorse of the shade garden, one of the few brightly colored flowers that thrive with little sunlight.
Downy mildew disease was the cause of last summer’s plague, which descended on impatiens throughout much of the northeast and parts of the rest of the country. Leaves of infected plants turn pale green at first, then develop downy, white growth on their undersides, and finally collapse. Stems also can eventually pick up infection. Needless to say, infected plants flower little or not at all.
Impatiens in Puerto Rico rainforest, El Yunque
But let’s look forward rather than wallowing in the past. Downy mildew can be expected this year wherever …