Wendy’s Co. is trying to shift more of its US lettuce supply to greenhouses amid climate change and bad weather that’s hurt the crop’s quality and availability.

“We are seeing more extreme weather events,” Chief Corporate Affairs and Sustainability Officer Liliana Esposito said in an interview. “It’s really about supply assurance, that you can create a more stable, less volatile supply.”

Crops grown outdoors are experiencing more weather-related disruptions, she said, adding that California wildfires have resulted in lettuce that can’t be used due to ash. Sufficient water access and extreme temperatures are also problems for outdoor crops, she said, while produce grown indoors has less risk of contamination.

The fast-food company, which sells lettuce on its sandwiches and in salads, already uses tomatoes from hydroponic greenhouses in North America. Wendy’s has also shifted its Canadian lettuce supply indoors in the past several years. But the US lacks capacity right now, Esposito said. The company is looking for new lettuce growers to diversify its supplier base.