Light and temperature extremes this time of year can stress plants in greenhouses and retail yards. Tender new growth and plants under water stress are particularly prone.
Faded, dull upper surfaces of most recently expanded leaves are often the beginning signs of sunscald. Sunscald -paper thin brown spots can occur on tender new growth and when cloudy weather is followed by bright sun and high temperatures. In greenhouses, shade cloth may be needed for some crops.
In outdoor yards, foliage burn caused by sun and especially wind, can also occur when greenhouse plants have not been acclimated.
Tina Smith, UMass Extension
Photos: Heat injury on impatiens
Sunpatiens showing stress - bright sun and heat followed by prolonged cloudy, cool weather