Thank you for reaching out to the Ask an Extension Expert group with your question about use of fertilizer on annual plants during hot weather.

Plants that are experiencing heat stress are unlikely to benefit from fertilizer. Consequently, avoid applying fertilizers during periods of hot weather or drought conditions. Instead, focus on watering your annuals adequately when they become dry.

Have you tested your soil to determine whether your plants need additional nutrients? A soil test can indicate which nutrients should be added to your soil for healthy plants. Use this link to learn more about using soil testing to aid in your gardening plans. If your soil test reveals that you need to fertilize, this recent heat wave will eventually break and then you will have the opportunity to fertilize later in the growing season.

Here are two links that provide tips for fertilizing plants during the warm months:

https://extension.umn.edu/yard-and-garden-news/hot-weather-fertilizer-tips-your-yard-and-garden

https://kentuckyhortnews.com/2019/08/28/summer-fertilization-of-annual-and-perennial-flowers/

Please reach out if you have additional questions. Thank you.