Shedding “Light” on Grow Lighting
Whether you cultivate plant clippings inside a greenhouse, are starting plants from seeds, or are turning an indoor corner into an area to grow herbs, supplemental grow lighting can have enormous affect on your success as a gardener. In this issue, we will shed some “light” on the ins and outs of grow lighting to help you understand the science behind and the benefits of supplementing the sunshine in your garden spot.
What We Know About Plants and Light
Most of us remember learning sunlight is important for plant growth because of photosynthesis. Plants derive energy from sunlight in order to create their own food to survive. And yet, there is much more to this process than we learned in the third grade! Understanding some of the science behind lighting will help you choose the right grow lighting, and create the best lighting conditions for your plants.
Light and Plant Cells
Plant leaves contain cells called photons. Photons are important because, using chlorophyll, they create the energy necessary for plants to grow, make food, flower, and produce seed and fruits. The number of photons each plant depends on the amount of light it has been exposed to. Photons rely on light to grow and reproduce. The more light exposure a plant has, the more photons are produced. More photons mean faster photosynthesis, which in turn means more energy for growth functions. Grow lighting can help spur plant growth, even in gloomy winter conditions.
Different plants require a different quantity of photons to perform at optimum levels. Peas, parsnips, and violets love regular shade. Marigolds, lavender, and peppers require full sun. It’s all about the rate at which each plant produces photons, and how many photons the plants need to grow to their fullest potential.
You may also remember “ROYGBIV” from your third grade science class. It stands for the color spectrums that humans can see- Red, Orange, Yellow, Green, Blue, Indigo, and Violet. This is called the visible spectrum. But, did you know that there are other spectrums that can’t be seen by us?
Let’s start with the basics. We know that chlorophyll gives plants their green color. We also know that chlorophyll is vital to photons producing energy during photosynthesis. Now we get a bit more technical. Chlorophyll absorbs light that is part of the PAR spectrum. PAR stands for photosynthetically active radiation. This spectrum contains light that benefit plants, but can’t be seen by humans.
One common type of grow light produces perceived “white light.” These lights actually cast off the full range of both the visible and PAR spectrums, which looks ” white” to the human eye. These lights can vary from very stark, meaning there are higher percentages of blue frequencies, to very warm, indicating higher levels of red waves. Because these lights contain the full spectrum, they are very useful in promoting plant growth. However, isolating the colors that plants respond to the most, red and blue, can help promote faster, healthier plant growth.
Research shows that blue spectrum lighting, or cool lighting, is beneficial to help leaves and stems grow. Red spectrum lighting has been found to assist in flowering and root growth. Grow lighting that casts a pink or purple glow are giving off a blend of red and blue wave colors. These lights are known as dual band lights. This type of grow lighting is particularly helpful in shaded spaces, light deprivation greenhouses, and in medical growing.
How Much Light?
So, if the human eye can’t see the whole spectrum, how do we know if the lighting we provide our plants is bright enough (or too bright) to be efficient? Simple answer, we don’t. Which means that it is vital to learn about the plants you’re raising.
A great place to start is to ask, “What are the conditions like in their natural habitat?” Cactus prefer dry, very sunny conditions that mimic their desert homes. Tropical plants like warm, humid environments with longer periods of day light. Knowing your plant’s “roots” will point you in the right direction in terms of their lighting requirements, and you can then optimize the growing conditions you are providing.
Large scale and commercial growers use expensive instruments called quantum flux meters. However, these can be expensive for home gardeners. More affordable (though less elaborate) light meters can help give an idea of how much light is in each area of your garden at a given time. With this information, and a careful eye to plant responses, additional tweaks to your grow lighting plan can usually be easy to discern.
What About Darkness?
Some plants cannot complete their growing cycles unless they spend a substantial amount of time in the dark. Plants like mums, hemp, and zinnias all respond to the lack of light by putting more of their energy into flowering or fruiting. Knowing whether you are growing “short-day” or “long-day” plants will help you create the best lighting conditions, as well as the best periods of darkness, for your plants.
This is why light deprivation greenhouses have become so popular in recent years. Knowing your plant’s growing cycle combined with being able to manipulate lighting to “trick” plants into cycling through their growing processes more quickly, is ideal for producing larger yields, more frequent harvests, or flowering on your schedule (such as poinsettias at the holidays).
Which Grow Lights Are Best?
There is no simple answer when it comes to choosing grow lighting. Taking into account the natural lighting available, the orientation of your growing space, the types of plants you are growing, and many other factors. For example, seedlings require a much higher volume of light to thrive. They are trying to develop healthy root systems, stems, and leaves full of those all-important photons. This requires a lot of light energy. Once your plant matures a bit, it probably won’t need as much light to grow. The best way to know exactly what kind of lighting your plants need is through observation, trial and error, and patience. Observing your plants regularly will help you adjust your grow lighting if they are getting too much light (brown, singed leaves) or not enough light (pale leaves and elongated stems).
Though there’s no one answer to the question of which grow lights are best, we do have some guidelines and recommendations for where to start when choosing supplemental lighting and fixtures.
• At least four 54-watt fluorescent tubes for seed starting; full spectrum vs. blue or red spectrum is up to you.
• If you choose full spectrum bulbs, look for “cooler” lighting that has a higher percentage of blue waves. These bulbs will be marked as 6500K (kelvin) and promote better foliage.
• MH, or metal halide, lamps provide more of the blue/green spectrum, are great for growing leafy plants like cabbage or peppers.
• HPS, or high-pressure sodium, lights are recommended to promote flowering in plants because of their higher red wave intensity
• Seek guidance from an experienced greenhouse expert whenever possible
We want you to know:
• T5 grow lights are high output lights that are affordable and readily available. They commonly used in both hobby and commercial greenhouses.
• LED bulbs are more energy efficient than fluorescent lights.
• Quality is important. Spending a little extra on lighting now, will save you a lot of money (and frustration) in the future. Invest in high-quality grow lighting and fixtures whenever possible.
• Don’t be afraid to experiment with different types of lighting and lighting combinations. Just make sure to observe your plant’s reactions to the lighting changes.
• We are available to help you choose the best grow lighting to meet your growing needs.
Now that you know a little bit more about how plants are affected by light and spectrums, you may be ready to add some supplemental grow lights to your growing space. If we can help, give us a call at 1-800-531-4769, or visit our website GothicArchGreenhouses.com, and let our team help you find the right grow lighting to create an ideal environment for your plants.