The best grow light bulbs

This site is built on published lumen figures - every room target and every roundup starts there. So it is worth being plain that on this page that measure does not apply, and why.

A lumen measures light weighted by human eye sensitivity, which peaks in green. Plants use red and blue light most and reflect green, which is why leaves look green. So a lumen figure describes exactly the wrong thing for a plant. The measures that apply instead are:

• PPF - photosynthetic photon flux, in micromoles per second. How many usable photons the bulb emits in total.
• PPFD - the same, measured as it arrives at a surface at a stated distance. This tells you whether the plant is actually getting anything.

A grow bulb that publishes neither is asking you to buy on the color of the glow.

SANSI 36W BR30 - the pick. It publishes both figures: PPF 65.6 micromoles per second and PPFD 265.58 at one foot. That second number is what lets you plan - it tells you what a leaf twelve inches below actually receives. The BR30 reflector aims light down at the plant, it fits any E26 socket, and SANSI states a color rendering close to 100, so it looks like normal white light in a room.
Cons: 36W is a lot of heat for a small enclosed shade; physically large for a BR30; and lumens are not published because they are not the relevant measure.

SANSI 10W, 3-pack - for a shelf of small plants. PPF 17.5 per bulb at 10 watts with a frosted optical lens, sold in threes. It runs cool, so it is safe close to foliage, and three bulbs light a shelf rather than one plant.
Cons: modest output - for light-hungry plants use the 36W; and no PPFD published at a stated distance.

Brightech Trilage - to light a group of plants. Three shaded heads with standard sockets on an arc, so three 10W grow bulbs can hang over a cluster of plants from a base standing out of the way. A grow bulb needs a socket that can be positioned above the plant, and an arc with standard sockets does that without any fixing. A clamp fitting with a standard socket is the alternative for a shelf - just avoid clamp lamps with integrated LEDs, which cannot take a grow bulb at all. The format is in swing-arm and clamp lamps.
Cons: the arc needs floor clearance behind the plants, and three bulbs means three purchases.

Brightech Eden - for a large floor plant. A floor lamp with a standard E26 socket, so it takes a grow bulb and stands beside a tall plant where a clamp could not reach.
Cons: its downward shade suits a single plant, not a group.

Start at the published distance. If PPFD is published at one foot, that is the distance the number describes. Closer raises intensity steeply and brings heat nearer the leaves; further drops it faster than it feels like it should.

Use a timer, not memory. Plants respond to day length, and a grow light that runs when you happen to notice is not a schedule. A smart plug or a simple timer makes it automatic - and stops a 36W bulb running around the clock. The running-cost arithmetic is in what does an LED bulb cost to run.

Use an open fitting. A 36W bulb makes real heat, and an enclosed shade traps it around the driver - the standard early-failure mechanism.

Full spectrum white over purple, indoors. Red-and-blue grow LEDs work and make a living room look like a laboratory. Full spectrum white does the job in light you can live with, which is the difference between a grow light you keep and one you unplug.