I live in Arkansas and have a variety of plants in pots on a covered patio with morning sun. Most obviously affected is the hosta. Due to the extreme heat, I water every day and the pot is plenty big. The leaves fade yellow and then dry from the tip in a very slow process.
Why Are My Patio Plants Suddenly Yellowing?
Certified GKH Gardening Expert
This is indicating that they are still not getting enough water. Even though they are in a big pot, in high heat, they need to be watered 2 times a day, due to the fact that water will evaporate very quickly (especially if they are clay pots).
You also need to make sure that the soil is thoroughly wet, especially if it has been allowed to dry out completely. Soiless potting mix can actually repel water if the mix is allowed to dry out and needs to be submerged in water for a few minutes to rehydrate it.