I have a small watering system for planter boxes and have been told not to water the leaves of the plant because it will turn them yellow. True or not?
Certified GKH Gardening Expert
Watering the leaves usually does not bring about yellowing on its own; however, stressed plants are prone to developing yellow leaves. It is typically not recommended to water foliage only because this can lead to fungal infections when the plants are not or unable to dry off due to poor air circulation. Therefore, bottom watering or drip irrigation is generally preferred. This does not mean you cannot use overhead watering, however. Simply do it at a time when you can ensure that the plants will have plenty of time to 'air out' so the foliage will dry. Don't do it when it's really hot (on sunny days), as this can actually burn plants. There are a number of reasons for yellowing of squash plant leaves--this article will explain the most common causes: https://www.gardeningknowhow.com/edible/vegetables/squash/why-squash-leaves-turn-yellow.htm