Cooler weather is approaching and it’s time to think about preparing your houseplants for their return to the inside. Tropical plants thrive outdoors during summer. Sometimes they get too accustomed to those conditions. When that happens they struggle when brought back indoors.

We need to prepare them for an environment with less light and less humidity. These two factors will stress plants. Stress affects their ability to produce sugars for growth and maintenance. It also makes them more susceptible to pests and diseases.

Therefore, we must gradually get plants accustomed to conditions that more closely resemble an interior environment. Ficus trees, for example will drop leaves like crazy if we take them directly from a sunny place to an indoor spot. Even if we place them in a south facing window they’ll still drop at least half of their leaves. If we don’t adjust their water to account for less photosynthesis they might lose even more. With proper conditioning you can still expect to lose about 25 percent of them.

It usually takes five or six weeks to completely acclimatize these trees to handle drastically lower light levels of the interior environment. We’re probably a little past that as I plan to move mine indoors in mid-November, weather permitting. Some more tender plants I’ll move sooner.

Before moving houseplants indoors we must also make sure they are free of pest and disease infestations. Insects are much easier to control outdoors. They become a much greater problem when plants become stressed from reduced light.

Mealybugs, scale, aphids and spider mites are common houseplant pests. They rob plants of energy and make them more prone to diseases. These little parasites also interact with the plants to produce a sticky substance called honeydew. This honeydew gets on carpet, walls, furniture and just about anything else in your house.

Pruning is something else to consider. I like to do it gradually and not too much immediately before moving plants indoors. Pruning encourages growth and we don’t want to do that with winter approaching. We want healthy plants, but we want their growth to slow down. For this reason fertilization going into winter is generally not desirable.

We also need to monitor soil moisture levels. When plants get less light they don’t use as much water. Excessive water means less oxygen to plant roots, which leads to root rot. Some plants, like jade plants, are especially susceptible. They can tolerate being slightly overwatered if they are outside. Indoors they aren’t as forgiving.

I admit I’m generalizing a little. Some plants don’t require as much light and must be kept in dense shade outdoors anyway. Their only adjustment is to the change in humidity. Philodendrons, pothos, African violets and peace lilies don’t require much conditioning.

Keeping houseplants on the porch or patio during the summer is something many folks enjoy. However, due to some of the necessary conditioning involved with moving them out in the spring and inside in fall some people don’t bother. I don’t know how many times I’ve heard people say that every time they move a plant it dies.

Bringing houseplants outside in spring isn’t necessary. Improved growing conditions do rejuvenate them though. Often by the time spring arrives some are pretty spindly. That’s usually an easy fix.

When we bring plants indoors we are generally slowing their growth rate down. There’s no harm in that. All we need to do is not give them mixed signals. Pruning and fertilizing encourage growth. Insufficient light means less energy will be produced to accommodate that. It’s a balance.

This croton has been conditioned and is ready to go inside.

Ted Manzer teaches agriculture at Northeastern High School (tmanzer@ecpps.k12.nc.us).