Take it Outside! Your Houseplants’ Summer Vacation

Monstera Philodendron and Orange Abutilon spending the summer on my canopied deck.

You’ve got overwintered geraniums and houseplants that have been cooped up indoors for months. You’ve noticed they’ve started packing their bags and are impatiently awaiting their summer vacation. They’re ready to burst through the screen door and start soaking up that gentle spring rain. When is the ETD? The answer is: they can go outside anytime now. As long as we are getting 15-20 degree weather, or hotter, geraniums and most tough leaved house plants can go outside.

Warning: Make the new light exposure as gradual as possible
The key thing is to make sure that you find a shady, sheltered spot to put plants in at first, for at least a week, (or more) to get used to the new amount of light. The difference between light indoors and light out-of-doors is vast, and not something that we humans notice, because our eyes and brains compensate for the difference: the iris, the entrance into the human eye, contracts and dilate rapidly between changes from indoors to out.

Everything you always wanted to know about footcandles
A footcandle is a measurement of light level. It’s the light intensity made by one candle at a distance of one foot. Compare the light levels of these situations:

Typical cloudy day: 3,200 footcandles
A sunny day: 13,600 footcandles
Indoor light for reading: Between 75 and 150 footcandles

A plant that has been in your living room, even one that has been near a window is going to go into shock when it goes from 150 footcandles to 13,600. The tissues that formed in a lower light situation can’t take it and will burn badly, just like we do. Once a leaf scorches, it’s done for. I was a little too eager last year and put my geraniums out in full sun without a shade period. A few of them scorched badly and looked pretty sad for more than a couple of weeks. They recovered and grew new leaves, but it’s a setback you don’t want. You want your plants to be strengthening their leaves, not having to grow completely new ones.

Here’s my problem: I don’t have much shade around the house — not until the trees leaf out. Then I’ve got more shade that I know what to do with, but until then, it’s bright and sunny everywhere. So this year I’m going to try a new technique. I’m going to wrap my plants in sheets to shield them from the sun for their transition period. After a few days of this, I’ll unveil them.

Beware cold overnight temperatures
While we are definitely having warm days, nightime temps can get pretty low, and if we get a sudden freak frost, with temperatures below zero you will need to bring the fellas back inside for the night. By the way, if you have plants like basil or impatiens, and any other warmth loving specimens, don’t bring them out till the 3rd week of May, the traditional planting weekend. Certainly any tomato seedlings should stay warm for as long as possible, even into the first week of June, if May remains cool.

Happy transitioning!


  1. Interesting post, thanks! Never heard about footcandles!
    It’s so tempting to get those plants out… But I got my lesson learned: in previous years, I had my plants frozen, some got overwet and rotten! I should be more patient!

  2. Helen .. I was reading your message about no luck with Pinky Winky Hydrangea and wondered if it is in a sunny enough spot .. they seem to take more sun than you think they would .. and that could make the difference in how it does for you ? I’m so curious to know what has gone wrong .. but maybe this Spring it will start to put growth on ! Don’t give up !

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