Which Grow Light Bulb Should I use?

Using  and identifying the correct Grow Light Bulb is one of the most important things an indoor garden can do. If they choose the wrong type, their plants won’t develop properly and you won’t receive an end result.

In this weeks blog, we’re going to explain exactly what each type of bulb does and what benefits they have on a plant’s different stages of development.

High Intensity Discharge (HID) Grow Light Bulbs

Easy to use and able to cover large areas, HID lighting can be broken into two categories: Metal Halide (MH) and High Pressure Sodium (HPS).

Metal Halide (MH)

Metal Halide or MH bulbs, as they are commonly known as, give off vast amounts of blue light. This blue light imitates the light of spring and summer, making them the best light for propagation and vegetative growth, promoting short intermodal length. These types of bulbs can either be used by themselves for plants like succulents, herbs or any other non-flowering plants. However, they can also be used on flowering plants during their growth periods.

High Pressure Sodium (HPS)

High Pressure Sodium (HPS) bulbs produce a more ‘redder’ light which aims to mimic the light of an autumn sunset. As this light contains more of a yellow and red colour spectrum, it is able to promote a higher production of flowers in flowering and fruiting plants. Typically HPS based lights are used to mimic the extended days that a plant is subjected to during late summer and autumn. These bulbs can only really be used in-conjunction with veg bulbs, such as, Metal Halide bulbs.

Fluorescent Grow Light Bulbs

Fluorescent bulbs are perfect for gardeners who want to reduce their impact on the environment as they are extremely energy efficient. Within Fluorescent bulbs there are numerous categories: strip fluorescents, high wattage compact fluorescents (CFL), warm or cool lights and high or low wattage. Typically these types of bulb are used in Full Fixture Grow Light fittings which can be purchased here

Due to Fluorescent lighting having a lower intensity than MH or HPS lights, they are better at providing close quarter lighting. This is because the bulbs do not dry out the growing media when placed close to a plant. This makes them perfect for use during a plants early stages of growth as well as for plants that need low levels of light, such as, orchids and ferns.Furthermore, due to their low light output, Fluorescent bulbs do not give off high levels of heat, meaning growers won’t need to install a cooling system in their indoor grow room.

When gardeners want to use a Fluorescent lighting during a plant’s vegetative stage, it’s advised that they choose a ‘cool white’ bulb. This type of bulb is also ok to use during a plant’s flowering stage, however, a ‘warm white’ light would be more suitable. This is because these types of bulb are stronger and provide more red light which is better at promoting flower growth.

Compact Fluorescents

Basically, Compact Fluorescents are exactly what their names imply… they produce greater light intensity than normal Fluorescent lighting and are available in a wide range of wattages. In addition, due to their small size, they can be fitted into most E40 Grow Light fittings.

If you’re only growing vegetative plants, such as herbs or lettuce you should be ok with using just a Compact Fluorescent bulb.

Does The Size Of The Bulb Matter?

The short answer is yes, you should pay attention to the size of your bulb. Plants that need a lot of light such as herbs and vegetables will need up to 60 watts of light per square foot of growing space. Below is a basic guideline for lighting a grow room with a HID bulb.