What plants need from your grow light

Plants are fascinating creatures. We know that sunlight is best, but why? what makes sunlight superior to artificial light for growing plants? Is it magical fairy dust that falls from sunshine and rainbows? no.

Sunlight is intense, direct sunlight can be as powerful as 120,000 lumens. It also contains the entire spectrum of visible light. But do plants really need ALL of that? well, no actually. Sunlight feeds all the life on earth, plants only use a small part of that. Photosynthesis is the basis of a plants life cycle, and it happens when chlorophyll cells in the leaves absorb light and a long with water, Co2 from the air, and nutrients absorbed through the roots, produce food for the rest of the plants cells, enabling it to grow and produce new tissues, even flowers and fruit.

An interesting fact, is that photosynthesis in most plants requires only two "colors" as we know them of the light spectrum: Red and blue. (They use small amo
unts of other colors as well but the majority of the light they need is red and blue) That is why some grow lights on the market, especially LED's which can be tuned to specific wavelengths have an eerie purple glow.

This need changes through the cycle of the plant though. During the vegetative stage, that is when the sprout is new and growing only leaves, it needs more blue light. When the plant starts to bloom and produce fruit, it gradually begins to need more red light. Using only blue light will result in a short but very leafy plant, using only red light will result in a tall spindly plant... I guess. Supposedly they figured all that out in a lab somewhere. I'd love to do some experiments like that but I don't have the time or money. mostly money.

Most light bulbs are labelled as to the color of light they produce. This is known as the "white balance" or "Color temperature". This rating is displayed in degrees kelvin, or just K. It has nothing to do with actual temperature, just color. The lower the number the more red the light produced is, the higher the number the more blue light is produced.

"daylight" fluorescent bulbs usually have a rating around 6400 or 6500k. This is closer to blue and is perfect for plants in a vegetative stage. "Warm white" CFL bulbs will usually have a rating around 2700k, which is beneficial for the flowering and fruiting stage. I've found the most success using a mixture. My current setup has 3 6400k bulbs and one 2700k. I used an LED panel once, but got the best results when I placed two 6500k tubes next to it.

Now when it comes to intensity, more is always better. Unless you're at risk of burning your house down you can't have too much light. Heat will damage the plants, as will UV light, but mere brightness isn't something you should be worrying about. The amount of light a plant needs changes through its life cycle. Seedlings can be started with very little light, usually one bulb is enough, but to grow to full cycle and produce fruit requires a lot more. I would say the minimum for most plants is 5,000 lumens for vegetative growth and 10-20,000 for flowering and fruiting. Thats a minimum, so adding more lights and more intensity will show immediate results and faster growth. There are many apps for smart phones that use your phones camera to give you a light intensity readout in "lux". Lux is basically the number of lumens reaching the sensor, so hold it where you plan to have your plants and that should tell you how much light is reaching their leaves.

60W CFL grow light, with foil tent

The closer your plants are to the bulb, the more light they will get, and you can also help to focus the light from your bulbs using tinfoil and home-made reflectors. A few sheets of tinfoil can easily double the output of your lights. I was able to get 5,000 lumens out of only 60 watts of CFL bulbs by making a "tent" out of tinfoil and electrical tape. In another post, I'll explain how we built it and include pictures.

Hydroponics with limited materials

One of the big challenges of designing a hydroponics system on an Island like this one, is the lack of materials. Some countries have big hydroponic supply stores where you can buy everything, even pre-made high end systems. In other places, you can still find nearly anything you need on the internet and have it shipped to you. Not so here. Where I live we don't even have a mail system, we can't even get letters mailed let alone packages. Also, even traditional garden centers do not exist in this country, gardening just isn't a thing. Farming is a thing, but here farming is walking into the jungle with a machete and chopping down any plant or fruit you need that just happens to be growing there.

Hardware stores, or "ferreterias" in spanish are a good resource. Here you can get basic materials like wire, pipe, tape, light bulbs etc. Nothing is labeled for gardening use so you need a bit of knowledge to know what to look for. Grow lights are not too difficult, My wife and I built our own grow light out of a metal shelf piece, tin foil, wire, and CFL bulbs. It has yet to catch fire, so thats good.

Selling seeds is rare also, so you will have to find most of you seeds in the wild, or take cuttings from the wild or from your neighbors (yes, I ask permission first). People here don't know Jalapeños, but I love them, so I went to the one market that sold them and bought the most shriveled up, over ripened Jalapeño they had. I got some strange looks for buying one single rotten pepper, but it was full of viable seeds. Sadly most of the sprouts died from salt and wind exposure, which is part of my inspiration for doing this hydrponic project. I also plan to grow lettuce, spinach, oregano and other herbs that are not available from the markets here.

I was able to find fertilizer in the capital on the mainland, but had to know what I was buying. Hydroponic nutrients can't be found here so I had to buy some other fertilizer by the kilogram, i'll go into more detail in another post.

In all I think I spent $10-15 on the entire setup, but it took some work and some creativity. In future posts I'll explain in detail each of the steps.