As the dog days loom, keep those containers watered well
When the heat of July and August arrives and summer fun beckons, the water needs of our plants are sometimes ignored, especially when gardening in containers. But, there’s no doubt about it: If you want beautiful containers that look gorgeous all season long, you have to make sure the plants receive regular and consistent moisture, especially during warm, dry weather.
The irrigation needs of each container are directly related to a few different items.
1. The volume of potting soil contained in the pot. Smaller containers need to be watered more frequently. So frequently, in fact, that if a small, clay pot is in the full summer sun, you may have to water it two or three times a day. In general, the larger the pot, the less frequently you’ll need to water it.
2 . The size and type of plants growing in each container. No matter what size container they’re growing in, bigger plants need more water (unless, of course, you’re growing a cactus or another plant with low-water requirements).
3. The age of the plants. Mature plants tend to need more water than immature ones. That means a container generally needs more and more water as the season progresses and the plants grow.
4 . The material the container is made of. Porous containers, like unglazed clay or moss-lined planters, dry out more frequently. If you want to limit how often you have to water, opt for glazed ceramic, plastic, metal, or fiberglass containers over terra cotta.
Rainfall also plays a role in how often you’ll need to water your containers. Invest in a rain gage and stick it right into one of your garden pots at, or just above, soil level. It will collect and measure the amount of rainfall that finds its way there. Most rain may never actually makes it into your container’s soil; it slides and bounces off foliage, which diverts it away from where it’s needed. You may find your rain gage empty, even after a heavy rain, simply because the leaves scatter the droplets before they reach the soil. Don’t assume a good rain has properly irrigated your containers. The only way to know for sure is to head outside and check the moisture level of your pots in person.
Another common mistake made by gardeners is when they use what I like to call the “splash-and-dash” method of irrigation. These folks dutifully head out to the garden every morning and sprinkle a little water on top of each plant, maybe splashing a bit onto the soil as they go. The foliage gets peppered with water, but the roots remain parched. The plants suffer, and the gardener can’t understand why their containers are underperforming when they’re “watering” them every day.
This kind of “splash-and-dash” irrigation, where a small amount of water is added every day, is not good for in-ground gardens or containers. Plants need deep, thorough irrigation that penetrates down through the soil to reach the entire root system. Shallow irrigation promotes shallow root systems that cannot access ample nutrition or withstand any amount of drought. Deep irrigation promotes deep, self-sufficient root systems. In containers, this means you need to apply irrigation water directly to the root zone, and you need to drench the soil repeatedly until at least a quarter of the water applied runs out the drainage hole in the bottom of the pot.
The trick to proper container irrigation is balance. Aim to supply your plants with plenty of water, but do it on an as-needed basis. Allow the growing mix to dry out a bit between waterings, but not enough to induce any plant stress.
Horticulturist Jessica Walliser co-hosts “The Organic Gardeners” at 7 a.m. Sundays on KDKA Radio with Doug Oster. She is the author of several gardening books, including “Attracting Beneficial Bugs to Your Garden,” “Good Bug, Bad Bug,” and her newest title, “Container Gardening Complete.” Her website is jessicawalliser.com. Send your gardening or landscaping questions to firstname.lastname@example.org or The Good Earth, 622 Cabin Hill Drive, Greensburg, PA 15601.