Tips for Choosing the Right Metal Halide Grow Lights

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Indoor gardening is growing in popularity. Though, many amateur gardeners have discovered that the same methods for growing plants indoors can be used to grow healthy vegetables and herbs.

When growing plants indoors, you need artificial lighting. Choosing the right lighting is one of the most important decisions that you will need to make. If you want your plants to thrive, they will need enough artificial sunlight.

Metal halide grow lights, high-pressure sodium lights, LED lights, and other options are available. But, how do you know which light to use? Whether you plan on growing vegetables, plants, or other herbs, you should look over the following tips to learn how to choose the right growing lights.

High Pressure Sodium or Metal Halide Grow Lights

Apollo Horticulture 400 Watt Metal Halide Grow Lights
Apollo Horticulture 400 Watt Metal Halide Grow Lights

There are two main options for grow lights – metal halide lights (MH) and high-pressure sodium grow lights (HPS). Both of these choices are much stronger than fluorescent or LED light bulbs. So, which one should you choose? Actually, you may want to use both MH and HPS lights.

Metal halide grow lights are often used during the vegetative state. They are used during the primary growth cycle of your plants. Once it is time for your plants to flower, you will switch to an HPS light. Though, this is not always necessary.

For example, if you are growing herbs or leafy vegetables, such as lettuce, you should be fine with just using metal halide grow lights throughout the entire growth cycle.

When purchasing grow lights, you can purchase ballasts that allow you to install both an MH and HPS light bulb in the same fixture. When it comes time to switch light bulbs, you can easily make the switch without changing your configuration.

What Wattage Do You Need for Your Grow Lights?

Along with choosing between different types of light bulbs, you need to consider the wattage of your grow lights. This will depend on the type of plant and the amount of space. With a large grow room, you will need more lighting. With a small grow closet, you will need less lighting.

In order to determine the desired wattage, you should measure your grow area. You do not need to measure the entire room or closet. You simply need to measure the amount of space used by your flower pots or hydroponics system. Multiply the width of your grow area by the depth.

For example, if you have your flower pots arranged in a 3×3-foot grid, then your total area is 9 square feet.

Next, multiply the required wattage by the total square feet of your grow area. You will generally only need between 25 and 40-watts per square foot. For example, if you are growing herbs, you may only need about 25 watts per square foot. For hardy plants, such as beans or carrots, you may want closer to 40-watts per square foot.

So, if you want 40-watts and you have 9-square feet of growing space, you will need about 360 watts of light. You can round this off to 400 watts, in order to make it easier to find the right light.

When Should You Use Fluorescent Bulbs?

Some gardeners prefer to use fluorescent bulbs when growing from seed. During the seedling stage, the lower wattage of the fluorescent bulbs offers more control over the amount of light that your seeds receive.

Though, since you will only need to worry about the seedling stage for several weeks, you do not necessarily need a fluorescent bulb. If your metal halide grow light can be positioned at the right height or if you have an automatic timer, you can use your MH light during the seedling stage.

How Long Should You Leave Your Lights On?

Typically, you will leave your lights on for about 14 to 18 hours per day. This will mimic the average duration of sunlight during the summer. Though, the actual amount of sunlight that is required will vary from plant to plant.

When you purchase a packet of seeds, the back of the seeds will generally include basic information for growing the plants. This will include instructions for planting your seeds, along with the time of the year to grow your plants.

If your plant starts growing at the beginning of Spring, then you may want to use a shorter light duration during the early growing stages. This is especially true during the seedling stage. While your plants are still seeds, they should get at least 8 hours of darkness, which means a maximum of 16 hours of sunlight.

What Are Light Reflectors?

Once you have chosen your lights and fixtures, you may also want to install reflectors. Reflectors allow you to deliver uniform light to your plants. A single light bulb will shine directly down on the plants below it. In order to deliver your light across your entire grow area, you may need to add reflectors.

There are two main types of reflectors – horizontal and vertical. Horizontal reflectors offer optimal distribution of light. You do not need a large reflector. A small amount of reflection can go a long way.

When adding a reflector, keep in mind that the temperature will increase. Your plants will likely thrive at specific temperatures. If your grow area gets too hot, you may need additional ventilation and fans.

Remember these suggestions as you begin preparing your indoor grow area. Metal halide grow lights are your best options for offering optimal lighting conditions for your plants. Though, you may also want to consider using high-pressure sodium lights for flowering plants.

The wattage is determined based on your grow area and a reflector can help distribute light evenly. In the end, if you are worried about getting the right type of grow light, you should simply choose an MH light bulb. It is the most well-rounded light and nearly provides a full spectrum of sunlight.


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