Not everyone has a sprawling backyard or a sunny window to grow plants. Or maybe you live in a region that has very few sunny days. No matter where you live and the outdoor growing conditions, you can grow herbs indoors and get a bountiful and flavorful crop – if you can provide the plants with the optimum amount of light.
You need about 7,000-7,500 lumens per square foot to grow herbs indoors. Herbs that need minimal lighting, such as mint and parsley, can grow indoors with 2,000 lumens per square foot. Those that require medium lighting can grow with 5,000 lumens per square foot.
Lights that are specifically designed for growing herbs indoors are expensive. You want to provide your plants with the right amount of light – so they don’t become leggy – but you don’t want to waste money buying brighter lights with more lumens that would be overkill. Read on as I explain how to figure out how many lumens you need to grow indoor herbs and how to choose the right growing light for your plants.
How To Choose the Right Growing Light for Your Indoor Herbs
Many plants can live and thrive without sunlight if you grow them under artificial lights.
If you want your indoor herbs to grow healthy and bushy and produce intense and fragrant oils, you have to provide them with adequate lighting at every stage of their growth.
Consider the following factors when buying grow lights for your indoor herbs:
Light Intensity Output
Lumen refers to the total amount of visible light produced by a source. The number of lumens you need for your herb plants depends on the following factors:
The Type of Herbs
Different herbs have different lighting requirements. Some need full sun to thrive, while others need part sun. The nature of the herbs you want to grow will determine the lumens you need.
The following chart lists the minimum lighting requirements of various commonly-grown herbs:
| Sunlight Requirements | Minimum Artificial Light Required | Herbs |
| Full Sun | 7000 lumens per square feet | Basil, Chives, Oregano, Marjoram, Rosemary, Thyme |
| Part Sun | 5000 lumens per square feet | Bay Tree, Dill, Cilantro |
| Low Sun | 2000 lumens per square feet | Parsley, Mint |
If you have been using incandescent bulbs marketed using the watt scale, you may find it confusing to visualize how bright a 2000-lumens light is. Or a lamp that produces 7000 lumens.
Here’s a helpful guide.
A standard 40-watt bulb emits about 450 lumens, while a 60-watt bulb produces 750-850 lumens. A 100-watt incandescent bulb, on the other hand, gives about 1600 lumens.
The Current Stage of Growth of the Herbs
Another factor that determines the number of lumens required by your herbs is their current growth stage. During the vegetative phase of growth when the plants are carrying out photosynthesis, you need to provide a minimum of 2000-3000 lumens per square foot.
The Distance of the Light From the Herbs
Lumens starts diminishing as soon as they leave the bulb. Therefore, you need to keep your herbs at an optimum distance from the source to ensure they soak in the maximum amount of light without getting burned. The following chart lists the optimum spacing for different lights:
| Light Source | Distance From The Tops of The Plants |
| Incandescent | 24 inches (60.96 cm) |
| Fluorescent | 12 inches (30.48 cm) |
| LED | 6 inches (15.24 cm) |
| Plasma LED | Approximately 2 inches (5.08 cm) |
However, how far you can place the light from the plants depends on the space available to you. The greater the distance from the plants, the more lumens you need.
Light Spectrum Output
Natural sunlight comprises red, orange, yellow, green, blue, and indigo color bands. These color bands make up the light spectrum.
Among these colors, the red and the violet bands are what’s needed most by growing plants.
Plants need blue light to grow healthy, lush foliage, and red light to produce chlorophyll, grow strong stems, and abundant flowers.
Ultraviolet light triggers the natural defense mechanisms in plants. When exposed to this light, plants produce essential oils that create a barrier to light. The production of essential oils causes the herbs to produce more essential oils that, in return, boost their flavor and smell.
If you grow your herbs indoors, you must provide them with lights that emit these colors.
However, not all lights produce the light spectrum you need to grow plants. For instance:
- Sunlamps: Produce too much of either red or violet rays that can harm your herbs.
- Incandescent lights: Produce primarily red, orange, and yellow rays.
- Fluorescent lights: Emit more yellow and green light.
You can grow your herbs under incandescent or fluorescent lights, but these do not provide the optimal lighting conditions. Your herbs will survive and grow but they will not thrive.
Alternatively, you can use a high-output T5 fluorescent tube to grow your herbs. However, this light has several disadvantages, which I will explain later.
An LED light contains almost all the rays in the spectrum your plants need during their various stages of growth. If you install an LED light, you won’t have to hunt around for separate lamps to use during your plants’ different development phases.
The full-spectrum plasma light is more efficient than LED lights. It is the closest to sunlight in terms of its spectral wavelengths. Unfortunately, it is expensive and not feasible to use unless you grow herbs commercially.
Can Any Led Light Be Used As Grow Light?
Any LED light can technically be used as grow light, but that does not ensure that your indoor plants will grow healthy. Regular LED lights are meant for human use; they do not contain adequate colors or light spectrum wavelengths that plants need to grow healthy.
LED grow lights are specifically designed to emit a particular spectrum of light that plants need to grow.
Light Type
Not all lights are suitable for growing plants.
For instance, you can choose to grow your herbs under cheap incandescent lights. However, these lights do not last long and consume a lot of power. Energy efficiency is an issue that you must consider, given that the lights will be switched on for up to 12 hours every day.
Additionally, these lights emit a high amount of heat. If you install them too close to your herbs, they can scorch them.
On the other hand, fluorescent lights come only in one size, which might not suit your indoor garden setup. Besides, these lights have to be replaced about once a year.
Though more expensive than incandescent and fluorescent bulbs, LED lights are highly energy-efficient, saving you hundreds of dollars in annual power bills.
Your Setup
Your choice of grow lights depends on the setup in your home. You have to consider the following factors:
- How much area (in square feet) will the lights cover?
- How many lights do you need?
- How many plants do you have?
- What are the dimensions of the planters?
- How much headroom do you have over the plants?
- Do you need multiple lights that emit different spectral wavelengths for plants at various stages of their growth?
You also have to balance your plants’ lighting requirements with your budget. However, I’d recommend getting the best lights possible as the cheaper options usually don’t last long or don’t provide good lighting and growing results.
Final Words
LED lights are the best growing lights for your indoor herbs and the most energy-efficient way to tend to your garden. To choose the right LED light for your indoor herbs, you need to understand the concept of lumens and keep in mind the specific lighting requirements of your plants.
You also need to determine the number of lumens your herbs need based on their growth stage, the number of plants you decide to cluster, and their distance from the light source.
