Houseplants on summer vacation? Time to bring them back inside

by David R. Clark, CNLP

If your houseplants have been outside this summer, start preparing now to move them indoors.

Here are some of my tips to get them ready for the move.

When to move houseplants inside

Move your houseplants to a shady place outside for one to two weeks to get them acclimated to the lower indoor lighting conditions.

Bring your houseplants inside before you turn on your furnace. If the plants are outside in cool daytime temperatures, your plants will be shocked when you put them into a house with the furnace blasting at 70 degrees Fahrenheit. You also want your plants inside when the nighttime temperatures hover at 50 degrees and no lower because this can damage the foliage.

Some plants should be left outdoors longer

Plants that should be left outdoors a bit longer include temperate carnivorous specimens (venus flytraps,  pitcher plants and sundews), zygocactus (Thanksgiving cactus or Christmas cactus) and Phalaenopsis orchids.

• Temperate carnivorous plants need this time to go dormant; they need a period of cold weather. Keep them outside until there have been one or two frosts and some snow. However, you can’t let them out when the weather is freeze and thaw, freeze and thaw; that could destroy their roots. So keep them cold by bringing them into a shed or garage where the roots won’t freeze. You can also keep them dormant at 37 degrees in the refrigerator. Keep them in this period of cold weather from November to March.
• Zygocactus (Thanksgiving cactus or Christmas cactus or holiday cactus) can flower any time of the year if given a cool temperature treatment. It also needs a short day and long night if they aren’t subjected to cool temperatures. You want to keep the cold treatment going as long as you can, 4 to 6 weeks, without damaging the plant. You can probably bring it in around Halloween. However, if the night temperature goes below 45 degrees, bring it in for that night, and put it out again at night when the night temperature is at 45 degrees or warmer.
• Phalaenopsis orchids can be treated similarly to holiday cactus. The phalaenopsis orchid can’t take nighttime temperatures below 50 degrees. Keep the cold treatment as long as possible. That signals the plant to form a flower spike, or even multiple flower spikes. When temperatures are consistently below 50 degrees at night, bring it in. Your orchid will flower in January or February. (You can buy phalaenopsis orchids any time in stores because growers do the cold treatment in greenhouses.)

Getting ready to move houseplants inside

• Inspect your plants for insects and mites. Look carefully at the leaf surfaces (both upper and lower), stem, leaf joints and growth tips. If you have a fern, look down into the crown of the plant and spread the fronds.
• Physically remove any observed creepy-crawlies, such as the mealybug. You can pick it out gently, or even better, touch it with a cotton-tipped swap that has been dipped in rubbing alcohol. DO NOT spray the entire plant with rubbing alcohol as you will cause cold damage from the alcohol evaporating. Don’t use your nails or you’ll damage your plant.
• Quarantine any infested plants away from the others. If you see damage to your plant, you probably have an infestation. If you see yellow speckles on the leaves, as if someone put yellow paint on a toothbrush and flicked the paint on the leaves, that’s an indication of spider mites. If you see dark spots on the leaf surface, the culprit is fungus or bacteria. If there are physical holes, you have caterpillars. Aphids can be found at the growing tips and usually are green in color.
• Thoroughly spray all surfaces of the plants with a garden hose to blast the offenders away. Make sure to get the soil wet also.
• A day or two before you plan to move your plants inside, soak the pot and soil media in a bucket of lukewarm water for up to thirty minutes. Any soil-borne creepies will float to the surface of the water where they can be skimmed off. Remove the pot from the water bath and wipe down the pot surface. Let the pot drain thoroughly.

Use pesticide—carefully

Optimally, we don’t want to bring insects or mites inside our homes because they could infest our other plants. One way to prevent this is by carefully using pesticides.

• If your plant is severely infested, it’s not worth your time trying use a pesticide. Throw out the plant.
• Know what you want to control. Don’t spray a pesticide if you don’t know what the pest is. For example, neem oil works on aphids, spider mites and thrip, but it won’t work on mealybug or tortoise-shell scale. If you don’t know what pest you have, contact the Master Gardeners in your county for help.
• Read the label on the pesticide! Before you do anything, read the label three times.
• Wear at least latex gloves, but nitrile gloves are better because they don’t let chemicals through the gloves. Once I was using a pesticide and my lips started to tingle because the pesticide was on my skin. That meant I was breathing in the vapor, too. I thought, “Oh my gosh, I just got zapped with insecticide!” Don’t let this happen to you.
• Preferably, do the spraying outdoors.
• When you are working with a concentrated pesticide that you need to dilute with water, measure carefully. If there is too much pesticide in the solution, you could have skin and respiratory issues, as well as possibly causing damage to the plant itself.
• Keep your pesticide tools separate from household items. Don’t use kitchen measuring spoons for pesticide. I have dedicated insect control equipment including the spray bottle. Make sure you label the spray bottle as pesticide, and what pesticide it contains.

Here are some insecticides you could use on houseplants. Make sure you know what you are trying to control and that the pesticide you use works on that pest.

• Safer’s insecticidal soap is probably the safest insecticide you can use. It works on direct contact with pests, removing the waxy coating of the exoskeleton and causing the insect to die. Use it on aphids, mealybug, scale, thrip, spider mite and whitefly.
• Spinosad is a natural substance made by a soil bacterium that can be toxic to insects. It is used in many pesticides and is good for thrip, spider mite, whitefly, aphid and scale.
• Neem oil is a vegetable oil pressed from the fruits and seeds of the neem tree. You can use it on insects, mites and fungus.
• Take Down Garden Spray is a product that uses canola oil as well as pyrethrin. (Pyrethrin comes from chrysanthemums.) It is an insecticide and miticide (pesticide for mites).

You can also make a pesticide that will work on leaf spots, fungal issues and insects, including aphids, mites, mealybug and thrip. This pesticide can remove a waxy exoskeleton coating with the soap, plus it smothers the breathing holes with oil.

• 1 quart water
• 1 teaspoon baking soda
• 1 teaspoon natural soap, such as castile soap, an olive-based soap, or Murphy Oil Soap, which has a potassium vegetable oil base. (Use the concentrated liquid Murphy Oil Soap.) Baby shampoo works, too.
• 2 teaspoons vegetable oil (Not motor oil!)

Spray the plant(s) thoroughly and let dry.

Applying the pesticide

• Preferably, do it outside.
• Don’t spray in full sun. The pesticide can create phototoxicity and burn the leaves in the sun. It’s like a person who is taking an antibiotic and can’t be in sun or they will get a skin reaction.
• Place the plant on the ground; don’t hold it in your hand. To get on underside of the leaf, place the plant on its side. You have to be very thorough.
• Read the application label for dilutions and timing. A good schedule might be to apply every three to five days the first week, and then once more the following week. For tough infestations, apply once more in the third week.