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E27 and B22 grow bulbs for UK lamps

A grow bulb is the least intrusive way to light one houseplant, because the lamp is already in the room. The fitting and the shade decide whether it is a good idea.

Two fittings, and which one you have

E27 is the screw cap, the Edison screw. B22 is the bayonet cap still common on British table lamps and ceiling pendants. Look at the old bulb: if it pushes and twists, it is bayonet. If it screws, it is E27.

The grow bulbs in the shortlist are E27, because that is what the makers list. A B22 lamp needs either a B22 grow bulb, which is harder to find in a full-spectrum white, or a B22-to-E27 adapter. The adapter only solves the metalwork. It does not solve heat.

Check the listing says 220–240 V and 50 Hz. A bulb described only as 120 V is the wrong mains.

Closed shades are the usual mistake

We haven't tested this kit. Specifications are as the maker states them (checked 13 November 2026).

The SANSI 15 W and SANSI 24 W listings both say not to use the bulb in an enclosed fixture or with a shade that stops it cooling. The bulbs get hot. A fabric drum or a glass globe that you cannot see through from above is an enclosed fixture for this purpose.

Use an open lamp, take the shade off, or use a holder that leaves the neck of the bulb in free air. Keep paper, curtains and the plant's own leaves off the glass. Distance from the foliage is a separate question, covered in PPFD and distance. The 15 W maker chart says 18–24 inches. The 40 W chart says at least 30 cm. Those are that maker's figures, not a rule for every brand.

Plugs, leads and what this page will not tell you to rewire

Prefer a fitting that arrives with a UK 3-pin plug. A two-pin Euro plug needs a proper fused adapter, not a loose shove into a UK socket.

If the lead has to cross a room, use one extension lead that is rated for the load, not a chain of them. For anything longer, or any doubt about the lead, Plankley's cable-size calculator and electrics pages are the place to check a portable lead. This site does not give instructions for altering fixed wiring. If the lamp holder is cracked, or the flex is baked hard, replace the lamp. Do not rewire it from a blog post.

A bulb with no timer of its own belongs on a plug-in timer. Hours are in hours and a dark period. The cost of leaving a 15 W bulb on for an evening is small, and the working is in running cost.