Grow Lights

[NYTomatoNewbie]

I was researching grow lights and this was extremely helpful. It explained the lighting metrics for plants, which are different than lighting metrics for human sight. This link has a chart showing the PPFD on the horizontal, hours on vertical, and DLI values based on those factors. It also explains what those metrics means and how distance from the light source affects those measurements.

https://redwing-farm.blogspot.com/2022/ ... y.html?m=1

[KaguyaCloud]

Ah, I remember reading that source. Everything it says is generally accurate. However, the main issue when you delve into details that precise is that there isn’t a practical means of doing it in a casual environment without spending hundreds or even thousands of dollars of equipment(PPFD meters, spectrometers, etc).

As a person who also fell into the same rabbit hole, my word of advice are these things:

-Buy any LX-1010B meter that can measure a maximum of 50,000-100,000 lux. Optimum tomato plant growth can be reached when growing plants at around 30,000-40,000 lux for 16 hours at the top of the canopy. Due note that this assumes that the light coverage is even throughout. For white LEDs you can divide lux by 70 to get an approximate PPFD value. From there, you can calculate DLI. For tomatoes, it’s recommended to have around 25-30 DLI per day.

-You don’t need expensive lights to grow plants. I use 2ft monios white t8 grow lights to grow all my plants, and they do fine. A pack of 6 is usually around 70USD and 3 of the lights can effectively cover a 24 inch by 6 inch grow area.

-Look at light response curves for certain species of plants to check what is most cost effective to do. Doubling your light intensity does not necessarily equate to doubling growth. In fact, for tomatoes, you get diminishing returns once you reach past 400-500 ppfd.

With this in mind and adequate nutrition provided, I’ve managed to grow tomato plants that can flower in around 3-4 weeks.

[NYTomatoNewbie]

I used the information to find a LED bulb that Listed the PPFD an then I calculated the hours needed to get the DLI of 30 and the proper height above the seedling. I didn’t have a space to mount or hang T8s so I am screwing a bulb into an adjustable arm lamp.

[Gin3ll]

My rules for using lights to produce plant seedlings:
- basic white shop lights
- 3000-5000 LUMEN
- 4000-6500 KELVIN
- 14-16 hours of light in the first 2 weeks
- 5-10 cm distance from the plant, adjust the height, if the light is strong you will see "burns on the leaves", if it is too far, the seedlings will elongate and be thin, and they will ''seek the light''

[Cole_Robbie]

When you look at a ppfd chart, some of them are measured in a grow tent with reflective sides, but others are not.

[zeuspaul]

if the light is strong you will see "burns on the leaves", if it is too far, the seedlings will elongate and be thin, and they will ''seek the light''

That's the metric I use. I use the screw in type. I have a dozen or more of various wattages and different cone angles. A couple of seedlings I'll use a small bulb. As I add more seedlings I swap the bulb for a more powerful one. I can adjust the distance using the clamp fixture attached to overhead strings.

LEDs.jpg