196-The Science of Lighting Plants Indoors, with Leslie Halleck-Encore Presentation

| Care, Podcast

The science behind the relationship between plants and light is complicated, but my guest on this week’s encore episode explains it in an accessible, easy-to-understand way. Her name is Leslie Halleck, and she is an expert on lighting for indoor growing. In our conversation, Leslie explains what gardeners need to know about light to raise houseplants as well as herbs and vegetables indoors.

Leslie is the author of “Gardening Under Lights: The Complete Guide for Indoor Growers.” Both veteran gardeners and those with no prior growing experience can benefit from this book’s advice on how to successfully grow ornamentals and edibles indoors. She has since released the book “Plant Parenting,” and in April 2021 her newest book, “Tiny Plants,” will be published.


Leslie Halleck

Leslie Halleck is a lover of plants, both indoors and out, and she certainly knows her stuff when it comes to light science and how it relates to plant health. (photo: Stacey Jeminson)


Leslie is a certified professional horticulturist with a Bachelor of Science in biology from the University of North Texas, where she focused on botany and plant ecology, and with a Master of Science in horticulture from Michigan State University, where her graduate research focused on greenhouse plant production using environmental controls such as lighting, photoperiod, vernalization and temperature. She has nearly 30 years of experience across several fields in the horticultural industry, and today she runs Halleck Horticultural, a consulting and marketing firm for the green industry.

The amount of light that plants receive drives photosynthesis, Leslie explains, but plants don’t measure light in terms of brightness. Rather, they quantify light in terms of volume. Plants are nature’s solar panels, turning light into energy, which they store and then convert to fuel for different processes for growth.

The white light of common lightbulbs is full-spectrum, while many grow lights on the market appear pink or purple because they are dual-band lights providing the most efficient light for plants to absorb: red and blue. Leslie says that blue light generally drives more vegetative growth, while red light stimulates roots, shoots, flowering and fruiting — and that’s why some high-tech grow lamps offer controls over the different bands of light.

For details on the importance of light, from how it affects plants on the cellular level to striking the correct balance between periods of light and periods of darkness, check out the show notes from the original airing of my conversation with Leslie.


Tomato vines growing in a greenhouse with supplemental lights is an example of lighting plants indoors

These tomato vines benefit from the natural light volume provided by the greenhouse windows as well as supplemental volume from grow lights. (photo: Leslie F. Halleck)


If you haven’t already listened to my conversation with Leslie Halleck on the science behind lighting plants indoors, you can do so now by scrolling to the top of the page and clicking the Play icon in the green bar under the page title.

How do you provide supplemental light to your indoor plants? Let us know in the comments below.

Links & Resources

Some product links in this guide are affiliate links. See full disclosure below.

Episode 037: Starting Seeds Indoors: The Non-Negotiables for Success, Pt. 1

Episode 038: How to Start Seeds Indoors: The Non-Negotiables for Success, Pt. 2

Episode 039: How-to Start Seeds Indoors: Digging Deeper, Pt. 3

Episode 083: Gardening Indoors: The Science of Light, with Leslie Halleck

Episode 108: Easy Ways to Make More Houseplants, Vegetables and Flowers

joegardenerTV YouTube: Seed Germination – Easy Tricks for More Success

joegardener Online Gardening Academy™: Three popular courses on gardening fundamentals; managing pests, diseases & weeds; and seed starting.

joegardener Online Gardening Academy Master Seed Starting: Everything you need to know to start your own plants from seed — indoors and out. 

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Growing a Greener World® 


Gardening Under Lights: The Complete Guide for Indoor Growers” by Leslie Halleck

Plant Parenting: Easy Ways to Make More Houseplants, Vegetables, and Flowersby Leslie Halleck

Tiny Plants: Discover the Joys of Growing and Collecting Itty-Bitty Houseplantsby Leslie Halleck

Exmark – Our podcast episode sponsor and Brand Partner of

Greenhouse Megastore – Our podcast episode sponsor and Brand Partner of – Enter code JOEGARDENER for 10% off your order

High Mowing Organic Seeds – Our podcast episode sponsor and Brand Partner of – Enter code JGSEEDS for 10% off orders of $50 or more

Disclosure: Some product links in this guide are affiliate links, which means we would get a commission if you purchase. However, none of the prices of these resources have been increased to compensate us. None of the items included in this list have any bearing on any compensation being an influencing factor on their inclusion here. The selection of all items featured in this post and podcast were based solely on merit and in no way influenced by any affiliate or financial incentive, or contractual relationship. At the time of this writing, Joe Lamp’l has professional relationships with the following companies who may have products included in this post and podcast: Rain Bird, Corona Tools, Milorganite, Soil3, Exmark, Greenhouse Megastore, High Mowing Organic Seeds, and Wild Alaskan Seafood Box. These companies are either Brand Partners of and/or advertise on our website. However, we receive no additional compensation from the sales or promotion of their product through this guide. The inclusion of any products mentioned within this post is entirely independent and exclusive of any relationship.

About Joe Lamp'l

Joe Lamp’l is the creator and “joe” behind joe gardener®. His lifetime passion and devotion to all things horticulture has led him to a long-time career as one of the country’s most recognized and trusted personalities in organic gardening and sustainability. That is most evident in his role as host and creator of Emmy Award-winning Growing a Greener World®, a national green-living lifestyle series on PBS currently broadcasting in its tenth season. When he’s not working in his large, raised bed vegetable garden, he’s likely planting or digging something up, or spending time with his family on their organic farm just north of Atlanta, GA.

0 Responses to “196-The Science of Lighting Plants Indoors, with Leslie Halleck-Encore Presentation”

  • Dawn Madden says:

    The science…the math…. loved it!!! I wish I knew about Leslie a year ago when I was picking out lightening. I purchased her book after her Q&A to the seed starting group and absorbed it in two days. I can’t wait to experiment and start growing inside. Joe, thank you for all your guidance and wonderful guests. Every time I think I have a favorite you keep bring us another amazing gardener! Dawn

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