When we grow plants in containers and raised beds, we are confronted with one basic difference from “in-ground” plantings: the roots of our plants are literally “contained.” This difference makes the proper care for potted plants and raised bed gardens slightly different from proper care for plants in the ground, specifically when it comes to watering.
Plants need water. Sure, we all know that. When it comes to containers and raised beds, I frequently see gardeners literally watering the plant, but not the pot. This can lead to problems. You might say, “Come on Chuck, what do you mean, I’m not supposed to water my plant?!” Let’s clarify that.
That’s great that you have the intention to water your plant. Remember that it is the roots of your plant that need the water, not the foliage. It is not our gardening goal to water the foliage of our plants (there are some exceptions, e.g. Tillandsia). We want to water the pot, not the plant.
Furthermore, if you water the soil only at the base of your plant, the edges of the container or raised bed can remain dry. When growing roots reach the dry soil at the edge of the pot, guess what happens?! The roots, as well as the plant, stop growing!
Alternatively, when you water, your goal is to thoroughly water the entire soil volume in the container or raised bed. When growing roots reach the edge of a pot or raised bed with thoroughly wet soil, guess what happens?! The roots and therefore the plant, continue to grow!
Here are a few examples of problems that can occur when the soil mass in your container or raised bed garden remains not evenly moist:
Most important! Plant growth slows or stops if the soil at the edges of the pot or raised bed is not receiving water. With each watering, be sure to thoroughly water the entire soil mass in the container or raised bed.
When soil on the edges of a container or raised bed remain dry, the soil mass can pull away from the container or raised bed. When you water, it is likely that the water will simply run down the edges and out the bottom of the pot; the soil and the plant subsequently fail to receive water. Rough up the soil or top dress with more soil, so that water is absorbed into the soil mass instead of running through it.
Watering an orchid plant, for instance, instead of the potting media may result in water sitting in the fold of the leaves, which can cause the leaves to rot.
Certain vegetable crops (e.g. tomatoes, squash, cucumbers, peas, beans) grown in containers or raised bed vegetable gardens are WAY more likely to get powdery mildew (a fungal disease; see previous article from 2019) when the soil mass is not kept evenly moist. When the roots of tomatoes, cucumbers, etc. reach dry soil, the plant stops growing, “gets sick,” and becomes more susceptible to contract the disease powdery mildew.
When growing roots reach dry soil at the edge of a pot or raised bed, guess what happens?!
The roots, as well as the plant, stop growing…among other things.
When growing roots reach the edge of a pot with thoroughly wet soil, guess what happens?!
The roots, and therefore the plant, continue to grow!
Water the pot, not the plant! And be sure you are having fun!