Using “herbs” in the normal sense of the work- hot peppers, mint, lavender, etc. The past couple of years I’ve used a 150 watt 5000K induction lamp with disappointing results. Everything but the peppers died out and the peppers basically went dormant until I brought them back outside in the spring. This fall I bought a 100 watt broad spectrum LED light.
What I’m having difficulty finding is “how much light in foot-candles do my plants actually want, and for how long” to make sure I’m doing it right. Looking online it seems most growers use different measurements like lumens per square foot, or units called PPFDs and DLI. FWIW I found a list of PPFDs and DLI for various plants, but have no idea how to convert them to foot-candles that I can measure.
Here are some pages that discusses conversion between PPFD and foot-candles. An exact conversion depends on the spectrum of the light source, but there are approximations used in these pages.
Success indoors with herbs over the winter depends not just on adequate lighting, but also on freely draining soil and cool-ish temps, with a preferable drop-off to upper 50s or so at night.
I’ve had OK results with basil and sweet pepper under a two-tube shoplight-type LED fixture. They don’t seem to need super-strong light unless one is going for heavy cropping.
I think you’re going to need a LOT more light. A single puny 100 watt LED bulb isn’t going to do the job, unless it draws 100 watts, not just puts out the equivalent of a 100w incandescent bulb.
We’ve got a couple of grow lights for starting seeds indoors in January, and one’s a 1800w LED contraption, and the other used a 200w CFL bulb (a HUGE thing with a Mogul base that draws 200w) like the kind they use to illuminate parking lots. Now we’ve got a 200w “corn” full-spectrum LED bulb in it- these are the replacements for metal halide lights for industrial purposes.
Something like this would be a good place to start:
“Broad spectrum” probably just means that it has a lot of different wavelengths within the visible range. If it doesn’t say “ultraviolet”, then it almost certainly doesn’t include ultraviolet, since ultraviolet is more difficult to get from LEDs than visible colors. And plants need at least some ultraviolet.
I haven’t tried LEDs. I built one using fluorescent bulbs. Works really well.
The light fixture is a 4 foot shop light with reflector, integral power cord, and pull chain. The light can accommodate four, 4 foot (48 inch), T8 fluorescent light bulbs. Each bulb is 32 W (F32T8). Two of the bulbs have a color temperature of 3000 K, two have a color temperature of 6500 K, and I staggered them when I installed them. The light hangs from an expandable garment rack 1 using a couple chains. This is really convenient; I can easily raise the height of the bulbs as the plants grow.
Yeah, the adjustable height is key, especially when starting seedlings you want it very close or many can get “leggy” and ultimately fail or be weak. In my limited experience, Brassicas get this bad (broccoli, cauliflower, cabbage, Brussels sprouts, etc.) Also a lot of light, which this setup looks good for that.
