Using Metal Halide Indoor Grow Lights

Crops that produce edible parts during vegetative growth, like spinach and culinary herbs, do not require anything stronger than fluorescent lighting.

fluorescent indoor grow lights can sometimes be used for the vegetative stage of plant growth. If your vegetative area is very small....for example, it will fit under 3 standard 4' fluorescent light fixtures, and you rarely have plants larger than 20 inches tall (i.e. lettuce, spinach, basil), I would advise you to use standard fluorescent shop lights exclusively. Use bulbs with the highest number of lumens you can find. Lumens=usable light to your plants.

Affordable 600 watt MH ligh, fully enclosed reflector with 6

Standard fluorescent lights will not be strong enough for most indoor gardening uses. When your vegetative area starts getting a little larger than 2' x 4', when you are growing plants larger than 20 inches tall vegetatively, and when you are growing vegetables or flowers under a flowering light cycle, your plants will require a light with more power than a standard fluorescent light can provide.

Replacement bulbs (lamps) of all sizes

In this case, using a metal halide grow light for the garden area is a great option. I always prefer to keep the heat from the grow light out of the garden by using a fully enclosed reflector that can be air-cooled. Look for a vent hole size of 6 inches (or bigger) to ensure efficient cooling of the grow light.

Flowering plants stretch in the absence of blue light. It is the blue light that keeps your growing plants short and stocky. Metal halide grow lights put out intense light high in the blue spectrum. It is the reason why metal halides produce a light that looks more white, compared to light from a high pressure sodium light (which looks more orange or yellow).

This intense blue-spectrum-rich light is just perfect for lush and vigorous vegetative growth, and is strong enough to produce great results during the flowering stage as well. Of course, only so long as there is also good air circulation and good temperature control. My best tips can be found on the following pages...

and always be sure to use an oscillating fan on your plants, (with the exception of your fresh clones).

How Close to Keep your Indoor Grow Lights

Light decreases very quickly with distance....keep your lights as close as possible, and use a thermometer in your 'hot spot' to tell how close you can keep them.

Below is a general guideline on how close to keep the tops of your plants from the bottom of your metal halide indoor grow lights. A good indoor/outdoor garden thermometer will help you determine if you can go closer or need to stay farther in your own setup.

  • 250 watt light............10 inches

  • 400 watt light........14-18 inches

  • 600 watt light........18-24 inches

  • 1000 watt light.......24-36 inches

Indoor Grow Lights Strategy

Metal Halide lights produce a white-looking light, because they prduce more blue light

Metal halide indoor grow lights, as well as "cool" white fluorescent lights, are very high in the blue light spectrum. Blue light is more beneficial to the healthy development of stems and leaves rather than the healthy development of fruits, vegetables, and flowers. For this reason, these grow lights are often used during the vegetative stage of plant growth.

HPS lights produce light that is orange to yellow in color. They produce little light in the blue spectrum.

The high pressure sodium light, on the other hand, is high in the red and orange light spectrum and very low in the blue spectrum. The orange yellow light encourages the healthy development of fruits, vegetables, and flowers. Upon flower forcing, a quick change in spectrum from a metal halide light (white/blue) to a HPS light (yellow/orange) makes many plants go into flowering very aggressively. This is why many people use a metal halide for vegetative growth, then switch to a high pressure sodium light for the flowering stage.

There are also many successful gardens that use HPS lights for both the vegetative AND flowering stages, or that use Metal Halide lights for both the vegetative AND flowering stages. Both lights are very intense, and capable of producing excellent results when used properly (including during flowering).

TIP- Changing from a vegetative photo-period to a flowering photo-period at the same time you change from a blue light spectrum to a red/orange light spectrum makes the plants very eager to begin flowering!

Not for Clones

Metal halide light is much too intense for seedlings and clones unless they are kept 3 or 4 feet away. This is a job much better suited for fluorescent grow lights. It will also cost much less on the electric bill this way, and will be much easier to keep the clone area at a comfortable 70 degrees.

Leave the indoor grow lights page and
Check out General Garden Lighting Tips

Learn how to grow hydro
(How to Maintain your Hydroponic Nutrient Solution)

AffordableGarden Design&Setup

(10 week update below)

Find out the cheapest and easiest ways to garden productively in this article.

Hi everyone, Jason from Jason's Indoor Guide here. When I got started with hydroponic gardening more than 24 years ago, my first garden used rockwool cubes and B.C. Nutrients....and I remember thinking to myself yeah, sure, there may be a lot of advantages to gardening with hydroponics, for example there are very few pest problems, therefore very little pest control, no weeding, no plowing or tilling the soil, no soil testing or having to add things into the garden soil, no watering the garden....but for someone who just wants to grow their own vegetables and have more control over their food supply and the quality of the food that they eat, the cost of constantly having to buy grow media and hydroponic nutrients makes this an expensive hobby for most people...

Epic Nutrient Change

I suppose when you take into consideration how much money you save NOT having to buy food at the grocery store, it is surely cheaper to grow your own food hydroponically even with the cost of high quality nutrients. Nevertheless, I didn't have a whole lot of money to work with and I needed to make my efforts as affordable and effective as possible....and in the last 24 years I HAVE learned a thing or two!

As you browse through Jason's Indoor Guide, you will notice all of the systems that I use personally are homemade systems. As I got 3 or 4 years of experience under my belt, I quickly adopted a preference to standing water systems and systems that use expanded clay pellets or lava rock, because the media is re-usable and it eliminates a huge operating expense. So once a hydroponic system is built, garden maintenance is minimal- check and adjust the nutrient solution daily, and to change it completely every 2 weeks....and the biggest operating cost is the hydroponic nutrients. (and the electric bill, lol)...

Homemade Cloner

And, regarding the cost of the nutrients....I experimented for about 3 years with making different compost teas and nutrient teas, but there is still a lot of expense $$$ associated with making high quality nutrient kelp meal, liquid seaweed, rock dust, bat guano, un-Sulfured molasses, worm castings. You can eliminate a lot of this expense by becoming an expert at making high-quality colloidal humus compost, and use your properly made compost as the basis of your hydroponic nutrient solution.

Unfortunately, I have been gardening for over 24 years and I have only just recently mastered this difficult skill....and even then, only because I happened to find a very easy to follow, high quality technique and decided to follow the instructions to the letter. I produced more high quality compost in just one week than I was able to use in a whole year! If you can master the technique, I highly recommend it. It is one of the top 3 things you can do to increase the productivity of your food production efforts, while at the same time decreasing the amount of effort required to grow all of your own food, and decreasing the total cost of operating your food production system.

And when I say decrease operating costs, I mean decrease them to almost ZERO, especially if you are producing your own nutrients...

High Efficiency

The ultimate solution to eliminate the cost of your hydroponic nutrients: Imagine a hydroponic system that does not require you to buy any nutrients, does not require you to make your own compost, and does not require you to brew your own nutrient tea. Seriously! No cost and no effort as far as providing nutrients to your plants! Plus, at the end of the gardening cycle you harvest all of your garden vegetables, PLUS YOU HARVEST FISH from the system--->


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This solution is aquaponics. If you are serious about producing all of your own food and being self-sufficient, this is the ultimate solution for reducing expenses (as much as possible), reducing the total amount of work required, and maximizing the productivity of your gardening efforts. I have been gardening for over 24 years, and it is the perfect food production solution in my opinion.

Produce garnden vegetables AND fish together. Eliminate fertilizer costs!

Besides mastering how to make high quality compost, learning aquaponics is one of the top 3 things you can do to increase your garden productivity, reduce your total costs, and reduce your total work. The product that I learned from is called Aquaponics4you. With all of my hydroponic gardening experience, the first time I came across the Aquaponics4you product I knew immediately that it was something very special! Place an aquaponics system outdoors and use the sun instead of grow lights, and you have reduced every garden expense to nearly ZERO!

The Same System/ 10 Weeks Later!

If you've found this site helpful at all, I would really appreciate it