Large swaths of the northern U.S. experienced their first frosty mornings last week. That crisp fall air serves as a reminder that many plants will need to be brought indoors soon. Here is a look at what plants should be brought inside before it gets much colder.

Time to Start Thinking About Bringing Some Plants Inside

For most Americans, this is the time of year when many outdoor plants should be covered or brought inside. When this happens largely depends on where you live as well as the hardiness of your vegetation. A general rule of thumb is to begin thinking about bringing plants inside once the mercury falls into the 50s overnight.

Tropical plants are not as hardy and will not thrive in temperatures under 60 degrees. This includes monsteras, geraniums, fiddle leaf figs, and pothos. Fruit trees that grow in containers should also be brought inside when the temperatures fall below this threshold. Some of these tropical plants might make it in temperatures that drop into the low 50s for a short time period, but they will not survive long periods of time at this level.

Plants typically associated with the autumn can survive in temperatures that fall as low as the 40s. Examples of hardy fall plants include goldenrod, chrysanthemums, and asters. Mums are another ideal plant to keep outside through October in most places. This is why these autumn favorites make such good porch decorations alongside those pumpkins.

Temperatures are not the only factor to consider when deciding when to pull the plug on the outdoor growing season. Drier conditions are also more conducive to plants being able to withstand cooler temperatures. For example, succulents can tolerate chilly nights as long as it is dry outside. According to Megan Brame, owner of Plantrums and host of “The History of Plants” podcast on YouTube, “Though it might seem counterintuitive, your succulents and aloes can stay out longer since they’re used to cold desert nights. She went on to say that "once you start getting nights that are consistently around or below 40 degrees and it’s wet, your succulents need to come in.”

How Wind and Humidity Factor Into the Equation

Gardeners also need to consider wind and humidity levels. The combination of dry air and windy conditions can accelerate the natural moisture loss from the leaves at this time of the year. This means that the vegetation could be more susceptible to damage even before the first frost of the season.

Experts say that a good rule to follow is to bring plants indoors when wind speeds are over 15 mph and humidity consistently hovers below 50%. It is also good practice to add a buffer of 5 degrees to the forecast overnight low. For instance, if the forecast is predicting a low of 55 degrees and you know that your vegetation struggles at the 50-degree mark, you may want to at least cover them up.

In addition to following these basic rules, your local greenhouse will be a good resource for advice that is specific to your area and climate patterns. Because temperature is not the only factor to consider, it is important to understand how the other atmospheric conditions in your area will play into how long you can leave those sensitive plants outside.

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