Hi, Roose. Welcome to ATP!
I have to admit that I don't know ferns. Is 800 lumens enough for them? It might depend on how close the bulb is, and over how much area the light spreads. I'm guessing that since many ferns are happy in shade, they might not need very bright light.
And a "spotlight" focuses the light better than linear shop lights do.
I'm used to fixtures with two 48" bulbs spreading maybe 5,000 lumens over 8-10 square feet, say 500 lumens per square foot. If ferns need that same brightness, 800 lumens would only cover 1.6 square feet.
... That article from Duke said they've evolved to handle low light levels, but HOW low? I couldn't find an answer online. Maybe the light you already had in that spot before adding the 800 lumen LED bulb, plus the bulb, will be enough.
If you put a book with small print where the ferns are going, and the light is enough to read easily, I'm guessing that's enough for a "part shade" plant. But hopefully someone with more of a clue will come along.
