I just unpacked a greenhouse I received as a gift, but there's no natural light in the cellar where it's set up. The shelves are approximately 55 inches long, 10 inches wide, and there's a 19-inch space between each shelf. I'm planning to grow herbs and greens on one side and flowers and fruits on the other using two-gallon nursery pots that are about 28 inches tall and 8.8 inches wide. I initially bought a GE LED grow light, but it's not going to be enough. Now, I'm thinking about getting some bar lights to install under the shelves above my plants. The challenge is that the distance from the top of the pots to the shelf above is only around 9 inches, so I'm concerned about plant height, especially if I put a compact strawberry plant on the bottom shelf. Is it okay for the lights to be this close to the plants? Am I overthinking it? Any advice would be appreciated!
3 Answers
Using the photone app on your phone is a great way to measure your light intensity! For vegetative growth, aim for around 150-300 PPFD (Photosynthetic Photon Flux Density), while fruit and flower stages need at least 600 PPFD. With the app, you can tweak the height of your lights until you find the perfect balance that your plants need. Just keep in mind that plants like strawberries do need a good amount of light!
Make sure to understand the inverse square law when setting your lights; it really helps with light intensity in small spaces! For example, if you get a Barrina T5 setup at 8 inches distance giving you 100 PPFD, moving the plant just 4 inches closer yields 400 PPFD. This adjustment is manageable for most plants. Just be careful with T8s though, as they can raise the PPFD too much quickly if you’re not careful!
Nine inches isn't too close for your setup, you can probably get away with placing them even closer! If your strawberry plants are around six inches tall, that gives you about three inches of space from the light, which is within a good range. Just make sure to keep an eye on the light intensity, especially since you’re worried about burns—typically, if they're thriving, you’re good!