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Your plants have been outside all summer- what should you spray on plants before bringing them indoors?
There are a lot of advantages to keeping houseplants outside for the summer- the bright light and increased humidity are ideal growing conditions.
The one question I always get asked is “What to spray on plants before bringing indoors so I don’t bring in bugs?”
In this article, I review the step-by-step process for acclimating your plants to an indoor environment without bugs!
When to Bring Plants Inside
The goal is to have plants acclimated to their indoor environment before night temperatures drop below 50 degrees Fahrenheit.
This is usually 2-4 weeks before the first frost date.
Plants that aren’t hardy (most tropicals and succulent houseplants) will incur damage or even death when exposed to temperatures less than 50 degrees Fahrenheit.
The first frost in my area averages the first or second week of October, so I like to have my plants indoors by September 15th.
Therefore, I begin the acclimatization process in late August or early September.
This allows me 7-14 days to prepare the plants for the indoor environment.
How to Move Plants from Outside to Inside
The first step is to move the plants to a shady outside location so that they only receive indirect light.
Begin this process as soon as possible- preferably 14 days before the date the plants will be moved inside.
This helps the plant adjust to the lower light levels and cooler temperatures that it will receive indoors.
Even if you use a grow light inside, it rarely provides the same intensity that the summer sun provides.
This is an important step because plants respond to drastic changes in light, temperature, and humidity by dropping large numbers of leaves!
The longer a plant is allowed to adjust to an environmental change, the better it will grow in its new location.
How to Debug Plants- The Steps
The first step is to visually check the top and underside of leaves (especially new growth) for the presence of insects.
Any plants that have a bug problem should be quarantined from the rest.
However, assume that if one plant has a bug problem, the remaining could have an infestation, even if there isn’t a visual presence.
Click here for information about treating and identifying specific bug problems.
For plants that are of a manageable size, I like to gently remove the pots to see the condition of the root ball.
Sometimes there is a visible bug that I can physically remove.
Occasionally pillbugs and sowbugs enter through drain holes and are easy to remove.
It’s also a good way to gauge if the plant needs more soil or if it should be repotted.
This is a great time to repot any plants that outgrew their container over the summer.
Next, while the plants are outside, use a garden hose and apply a strong stream of water to the foliage.
This is an effective, organic way to remove any small insects and their eggs.
I also thoroughly water the soil.
The Spraying Process
Then spray the underside and leaf surfaces with insecticidal soap made for horticultural use.
Read and follow all label instructions.
Return the plant to the shady outside location for 5-7 days.
Then, apply the insecticidal soap a second time to the leaves.
Maintain the plant in a shady location and after another 5-7 days it’s time for the final preparations for the plants to come indoors!
If you feel there may be a few rogue bugs in your plants’ soil or pots, the next step will take care of them, otherwise, it’s optional.
On the day you plan to move the plants indoors, immerse each plant’s pot in a bucket of lukewarm water for 15-20 minutes.
This will cause any remaining bugs in the soil mix to float to the surface of the water.
Then thoroughly spray the leaves again with insecticidal soap.
This third application of insecticidal soap will kill any remaining insects that were in an early developmental stage and ensure your plants are bug-free!
The final step is to wipe the surface of the containers to remove any soil or debris.
When the pots and leaves are dry, they are ready for their new home indoors!
Example Midwest Timeline for How to Move Plants from Outside to Inside:
September 1- Move plants to a shadier location outside
September 2- Inspect plants for bugs; remove yellow, brown leaves; repot any plants as needed; spray plants with insecticidal soap
September 9- Spray plants with 2nd application of insecticidal soap
September 15- Soak pots in lukewarm water to remove possible bugs in the soil (optional), 3rd spray with insecticidal soap, and place indoors!
Tips for What to Spray on Plants Before Bringing Indoors
- Avoid spraying plants on hot days. This can stress the plants and cause burning.
- Keep plants in a shady, cool location when spraying. The combination of sun and soap can cause leaves to burn.
- Several brands of insecticidal soap do not recommend using it on delicate ferns, check the label first.
- There are a lot of Internet “recipes” for making your own insecticidal soap. Avoid this temptation as household cleaning products weren’t designed for horticultural use. They have detergents, dyes, and fragrances that are not designed for use on plants. Some may work, while others may be extremely caustic to plants.