Chances are, you have two problems with your tropical potted plants: Whether they’re planted inside or outside in your shade garden, you might have pesky flying gnats; or you are losing plants more often than you should.
Well, both of these situations are caused by loving our plants to death—in other words, we overwater them.
We live in the desert, right? So all plants need a lot of water, right? Not necessarily so.
Signs of overwatering include:
- Yellowing leaves that remain soft and fall off the plant.
- Soggy roots.
- Smelly soil.
- Those aforementioned gnats.
In the desert, most true tropical plants—such as gardenias, camellias and what we know as house plants—need to be grown in the shade, or inside during the colder seasons. Plants grown in the shade do not have hot, direct sun to dry them out, so they will stay moist for much longer than those in the sun.
The larger the pot, the more water it will hold. If you stick your finger in the soil, you may feel that the top 4 inches are dry—but think about where the root system is for your plants. An established plant in a 12-to-16-inch-tall pot will have roots down 8 inches. A water meter can be helpful to test the moisture in the root zone. When using one, you will only want to water when the meter is registering toward the dry side.
General watering guidelines:
- Outdoor potted shade plants need water in the summer once or twice a week. In the winter, a watering every seven to 10 days will be ample.
- Many indoor plants only need to be watered every three to four weeks. Really!
As for Those Pesky Gnats
Those gnats are typically fungus flies. They’ll appear after you’ve overwatered your plants, since the eggs hatch with excessive soil moisture. Allowing the soil to dry between waterings usually eliminates the problem.
You can purchase yellow sticky traps at hardware stores or nurseries to eradicate the adults—but the larvae and eggs remain in the soil, so you’ll still have to isolate the plant and let the soil dry out to prevent the maturation and production of more flies. The cycle from egg to fly is three weeks—so watering every three to four weeks makes sense.
Should you have a chronic problem, check with an exterminator about treating your soil. My exterminator eliminated my pest problem by using a solution that’s nontoxic to plants. Remember, the eggs of fungus flies are present in basically all soil, so appropriate watering is key.
Important: Take action as soon as you see one or two gnats. If you wait, you’ll have a much larger problem.
Marylee is the founder and former owner of The Contained Gardener in Tucson, Ariz. She has become known as the Desert’s Potted Garden Expert. Email her with comments and questions at firstname.lastname@example.org, and follow the Potted Desert on Facebook.