Indoor Gardening–Let Light Shine

Let the Light Shine

For many gardeners, the introduction to artificial horticultural lighting (“grow lights” as I’ll use for slang) is one of practicality – get an early start on sprouting seeds for outdoor planting. Transplanting young plants with established roots into your garden not only avoids the risk that seeds don’t germinate properly due to spring weather conditions, but it can also improve yields at harvest. You’ve essentially extended the growing season by a few weeks (or more). And while it’s certainly possible to utilize a south-facing windowsill as the launchpad for this endeavor, there are distinct advantages to supplementing the sun’s rays with a grow light. By increasing the intensity of light reaching your seedlings, you reduce the risk of their stems becoming leggy and weak, you increase the size to which they can grow prior to moving outside and you gain flexibility as to where you place them (i.e., you’re not longer tied to that windowsill).

The other grow light location that frequently comes to mind is greenhouses. Fixtures placed every dozen feet or so, equipped with glowing orange bulbs radiating heat down towards the canopy keep warm-weather plants growing even in the dead of winter. Days can be extended to prevent short day plants from flowering too soon and cloudy stretches don’t slow photosynthesis. Just as with sprouting seeds, though, this use of artificial lighting to improve production in the garden is still just a supplement. It’s not a full replacement for the sun’s powerful, life-giving rays.

Enter the less commonly considered application of grow lights, year-round indoor food production. Until the past decade, growing food indoors simply wasn’t practical as it was with seed starting or supplemental greenhouse lighting. The cost was prohibitive, the technology was inefficient, and it was frankly a bit dangerous. Grow lights become the tools of underground cannabis growers because only a crop selling for thousands of dollars per pound

would justify the electrical cost. Doubtless, they acquired a stigma. Even if you were just growing tomatoes in your basement, would the DEA come smashing through your front door because they saw you leave a grow shop with lights in-toe? Because your energy usage suddenly jumped? Because your house was emitting an unusual heat signature?

Fortunately, horticultural lighting technology has made giant strides over the past couple decades, to the point where it’s even helped shift attitudes. The entry and continued development of light emitting diode (LED) technology into the market is debatably the primary reason. Where the old technologies of High Pressure Sodium (HPS), Metal Halide (MH) and even fluorescent bulbs (to an extent) were hot, energy inefficient and not without some level of danger, LED technology is exactly the opposite. Today, you can spend less than $100 on an LED to grow lettuce in a 3’ x 3’ space 365 days a year for 10 years without ever changing a bulb and with a monthly addition to your electrical bill of only a few dollars. While LED lighting has re-

solved the practicality of growing at home, its also introduced a new challenge of abundance. The inexpensive nature of LEDs has created a competitive market of brands, all touting unique features and designs, although many are produced from identical components. Trying to sort through the daunting array of options is overwhelming, but there are a few areas to pay close attention.

Outside of cost, the first question to ask is: How much usable light will reach my plants? At risk of being simultaneously too technical and too simplistic, it’s helpful to understand that light is actually electromagnetic radiation – yes, the same stuff our microwaves use to heat up food and our radios use to pick up a station. The difference is in the lengths of those radio waves. Wavelengths between 400 and 700 nanometers (nm) represent a form of light called photosynthetically active radiation, PAR for short. This is the light plants can use to perform photosynthesis. LED grow lights will almost always be accompanied by specifications indicating the quantity of PAR provided to your plant at varying distances, measured in “ppfd.” The farther away you place the light from your plant, the more dispersed the plantavailable light becomes by the time it reaches the canopy, meaning that a light providing 1,500ppfd when it’s placed 8 inches above your plant may only provide 150ppfd at 6 feet.

These measurements are important in purchasing the right type of light for your application. For example, seedlings need only a small amount of light, around 100ppfd. Leafy greens do fine with a few hundred ppfd, but flowering plants like peppers and tomatoes thrive under a thousand ppfd during fruiting. As a general rule, the higher the ppfd, the more expensive the light.

The other question to ask is in regards to color temperature. This is measured in Kelvin and typically ranges from 2,000K (warmer) to 8,000K (cooler). An easy way to think about Kelvin is the “warmth” of a bulb. When you’re replacing a light bulb in your house, you may want a softer, warmer bulb to create a relaxing environment. That would fall in the 2,700K-3,000K range. If you want a cooler light that provides more of a daylight environment, 4,500K-6,500K would give that feel. The temperature of light produced by LEDs is precisely controlled by the diodes used in their production and is typically indicated in their product specifications or on their packaging. Plants like lettuce and kale tend to prefer higher Kelvin values with more blues and whites. Flowering plants like peppers and tomatoes prefer lower Kelvin values, made up heavily of reds and oranges, especially when flowering and fruiting.

JASON MISPAGEL Indoor Gardener

Jason Mispagel is the co-owner and operator of Year-Round Garden, a grower’s supply center serving both home and commercial customers since 2016. To contact Jason, call 816-216-6917 or jason@year-roundgarden.com.