Just like you, your houseplants can benefit from summer vacation. The brighter light increased humidity, and air movement outdoors can rejuvenate plants that have been inside all winter. But as autumn nights get colder, houseplants that have sojourned on a shady deck or porch, need to be brought back indoors.
Most houseplants come from tropical or mild-winter areas. Cold air will damage their leaves and cause flower buds to drop, so you need to take action before cold nights really settle in. When night temperatures start dipping below 45-48°F, it’s time to end the vacation and you should start bringing plants inside
But before you make the move, make sure to check for hitchhiking pests that may have established a home on plants during the summer months. There are two types of pests you might find: leaf-dwellers and soil-dwellers.
Insects that feed on plant leaves include Aphids, Spider Mites, Scale, and Mealybugs. Other hitchhikers could include Spiders, Gnats, or Lacewings. Examine leaves and stems carefully. Check leaf undersides in particular; many insects prefer to hang out under leaf surfaces. You might also spot insects where the leaves meet stems.
You can knock off many insects with a strong spray of water. This will also help remove any dust that has settled on the leaves. Use a hose with a spray nozzle so you can direct water underneath the foliage. Apply a gentle spray; too hard a jet will not only dislodge insects but also tear leaves. A pressurized sprayer like the ones used to apply insecticides can also be used to apply water to leaf surfaces.
For smaller specimens, consider dunking the entire plant into a water-filled sink or 5-gallon bucket of water for 15 minutes. This will dislodge the bugs on leaves or in soil. Add a few drops of mild liquid dish soap to the water as a further deterrent to insects. Just make sure you thoroughly rinse the plants with fresh water an hour after soaking.
If after washing leaves and allowing them to dry, you still notice insects, apply an insecticide such as Natria Insecticidal Soap. In fact, many gardeners routinely spray plants with Natria Insecticidal Soap or other Natria products as a precaution before bringing them indoors. When you move infested plants indoors, keep them isolated for about six weeks so you don’t spread any surviving bugs; make visual inspections to ensure pests are gone. Retreat as necessary. Always read and follow label instructions.
Insects can also set up shop in the soil of potted plants set outside for the summer. They include Slugs, Sowbugs, Earwigs, Fungus Gnats, and Ants. For plants in smaller containers, gently slip the root ball from the pot and examine the soil. Typically, Slugs, Sowbugs, and Ants will be found on the outer layer of soil of the root ball near the drainage holes. Knock them off with a finger, stick, or old spoon.
Fungus Gnats and Earwigs usually congregate in the upper layers of soil. Remove any dead foliage or flowers from the top of the root ball, and dunk the soil into the water as described above.
For houseplants in large containers, where slipping the root ball from the container or dunking the entire pot is impractical, apply a properly labeled insecticide to the soil surface and around the drainage holes. If insects were present in the soil near drainage holes, consider repotting the plant next spring and placing wire mesh or hardware cloth inside the base of the pot to exclude insects.
Other Tips Before You Bring Plants Indoors
Thoroughly water the plants while they are still outside. Make several passes with the hose so any accumulated salts are leached out of the root ball; then fertilize. Letting the container partially dry before bringing indoors will lighten the weight.