Light is essential for a successful grow. Indoor growers using grow lights must mimic mother nature to achieve a bountiful harvest. Inadequate light spacing can cause damage to your plant (placing your light too close to your plant can potentially burn it) or can slow growth drastically (placing your light too far from your plant). The key is to prepare yourself before you start your grow to minimize these preventable mistakes. So, what is the ideal grow light distance from plants? Since there is no set in stone distance, the answer depends on a number of factors that each grower must address before starting their grow. I decided to write this short blog because it is a good topic to discuss.

Grow Light Hangers

If you are a new grower, do yourself a favor and invest $9 dollars for a set of light hangers. They are totally worth the small investment. Light hangers allow you to move your light easily and accordingly. This will set you up for success. Rope hangers also work great.

Grow Light Meter

Grow light meters are also very useful for determining light output. They range in price depending on the quality you wish to achieve. An entry level par meter costs about $15. A professional meter like the Apogee par meter can cost more than $500. No mater the price, adding a grow light meter to your garden is an effective way for measuring your light output.

Grow Light Distance from Plants

There are a lot of variables when considering the appropriate grow light distance from plants. If you are a new grower, here are a couple quick notes when shopping for lights. Photosynthetically active radiation, or more commonly referred as ‘PAR’ is the light used by plants. When purchasing a new light, choose one that produces the highest PAR rating with the widest possible light spectrum. You also want a light that has a Kelvin spectrum between 3,000 and 6,500.

When determining the grow light distance from plants, a good rule of thumb is if it’s too hot for your hand, then its definitely too hot for you plants. I use this rule with all grow lights. Place your hand under your light at the distance you plan on hanging. If it feels hot, then consider backing off to avoid burning your plants. The goal is to find that sweet spot. The closer the better as long as you don’t burn your plants.

• Side Note: younger plants don’t need as intense light. If you have young clones or seedlings, back off the distance between your plants and your light and gradually move it closer as they become bigger and stronger.
• Side Note #2: most new lights come with instructions that usually include a suggested hanging distance. While useful, I would still recommend conducting the hand test to double check.

HID – High Intensity Discharge Light Systems

HID lighting systems include metal halide (MH) and high pressure sodium (HPS). These light systems generally range between 150 and 1000 watts depending on the size of your grow.

• 150 – 175 watt HID systems cover 2×2′ gardens. These lights should hang between 10 – 14 inches above your canopy.
• 250 watt HID systems easily cover 3×3′ gardens. Place these lights 12 – 20 inches above your canopy.
• 400 watt HID systems can cover 4×4′ gardens. Hang these lights between 12 – 26 inches above your canopy.
• 600 watt HID systems can cover 5×5′ gardens. Hang these lights between 18 – 26 inches above your canopy.
• 1000 watt HID systems can cover 6×6′ gardens. These lights need to be placed between 24 – 32 inches above your canopy.

LED Lights

LED light systems are awesome! Now a days, I tend to favor LED lights for several reasons. First, they offer a much larger range of light spectrum when compared to HID systems. Second, they use a lot less power, produce very little heat and have a longer life span. They are also very quiet. And if that’s not enough, they’re also a lot cheaper to purchase! Newer models like the Mars Hydro TSW can be dimmed!

• The recommended hanging distance above plants depends on how powerful your LED is, but here’s a range that is suitable for most LED lights: Seeding: 24 – 30 inches; Germination: 24 -30 inches; Veg: 18 – 24 inches; Bloom: 12 – 18 inches above your canopy.

Fluorescent Light Fixtures

Fluorescent bulbs are cheap. They come in a number of sizes and supply cool and diffused light. Fluorescent lights are weak when compared to HID and LED systems. These lights must be placed between 2 – 6 inches from your canopy.