Grow Lights for Houseplants: How to Choose Spectrum, Brightness and a Timer

Start with how much light your plants need

Brightness is the spec that matters most. Most houseplants need much less light than the large grow panels sold for vegetables. House Plant Journal publishes targets measured at the leaf and based on 12 hours of light a day. Pothos, ZZ plant, sansevieria, peace lily and aglaonema are listed at about 100 foot-candles (around 20 µmol/m²/s) to stay healthy and 200 foot-candles (around 40 µmol) to grow. Monstera, philodendron, hoya, calathea and most other common foliage plants are listed at 200 to 400 foot-candles (40 to 80 µmol). Ficus, succulents, croton, jade and African violets are listed at 400 to 800 foot-candles (80 to 160 µmol). The same author notes that a fiddle-leaf fig with less than about 400 foot-candles will lose most of its lower leaves.

The University of Illinois Extension gives typical indoor light levels for comparison. A spot a few feet from a north window gets about 75 foot-candles. A spot directly in front of an east or west window gets about 300. Directly in front of a south window, it can reach about 1,500. Full outdoor sun can reach 10,000 to 12,000. So a plant that sits deep in a room with few windows is often getting less than its listed minimum.

On spec sheets, brightness shows up as PPFD (µmol/m²/s) at a stated distance. House Plant Journal suggests a rough conversion for white LEDs: PPFD is about 0.2 times the foot-candle reading. That lets you check a cheap foot-candle or lux meter against a product's claims. The author recommends a dedicated meter over phone apps, because apps estimate from the camera and give only a rough idea.

• Low-light foliage (pothos, ZZ, snake plant): about 20–40 µmol/m²/s at the leaf

• Most tropical foliage (monstera, philodendron, hoya): about 40–80 µmol/m²/s

• Ficus, succulents, African violets: about 80–160 µmol/m²/s

• Citrus and other sun-lovers: about 160–400 µmol/m²/s, and the source says they do best outdoors in warm months

Spectrum: white light is usually enough

The University of Illinois Extension says plants need blue and red wavelengths for photosynthesis. It also says cool white fluorescent tubes work well for foliage plants, and that blooming plants do better under incandescent light or bulbs sold as grow lights. Iowa State University's Yard and Garden FAQ goes further. It says a fixture with two 40-watt fluorescent tubes, one cool white and one warm white, gives houseplants enough light. It adds that bulbs sold as plant lights are expensive and generally not worth the extra cost.

For LEDs, the reviewers at Bob Vila recommend full-spectrum white as a light that covers every growth stage. House Plant Journal says white LED light is strong enough to grow any houseplant. It also warns that red-blue ('blurple') LEDs throw off foot-candle meter readings, so you can't easily check how much light your plants get. For a living room, that settles it for most people. A white light looks normal, lets you see the true leaf colors, and can be measured.

If the light is on display, check its color temperature and color rendering. Soltech's Aspect pendant, for example, is described as 3000K warm white. House Plant Journal measured its color rendering index (CRI, a score for how true colors look under a light) at 97.5, close to the 98 the maker claims. Spider Farmer's SF600 bar mixes warm white (2800–3000K) and cooler white (4800–5000K) diodes with deep red (660–665 nm) and far-red (730–740 nm), according to its product page. That mix is aimed more at growing vegetables than at looking good in a room.

Timers and hours: how long to run the light

Light duration matters as much as brightness. House Plant Journal treats the total daily dose (DLI, the daily light integral) as brightness multiplied by hours. That means a dimmer light can partly make up the difference with a longer day. The University of Illinois Extension says 14 to 16 hours of supplemental light a day is enough for plants in low light. It also says not to go past 16 hours, because plants need a rest period. Iowa State suggests 12 to 14 hours. House Plant Journal's tables assume 12.

Some plants need darkness to flower. Gardener's Supply notes that Christmas cactus, kalanchoe and poinsettia only bloom when they regularly get less than 12 hours of light a day, with long stretches of uninterrupted darkness. If one of these shares a shelf with foliage plants on a 14-hour schedule, it may not bloom.

Gardener's Supply's advice is simple: get a timer, because no houseplant needs 24 hours of light. Built-in timers vary. Bob Vila's reviewers list 4, 8 and 12-hour settings on the Lordem ring light and the LBW stand light. They note that the Mosthink strip timer tops out at 8 hours, which is short of the 12 to 16 hours the extension sources describe. Lights without a timer, such as the Spider Farmer SF600 and the GE grow bulb, need a separate outlet timer or smart plug. Spider Farmer sells a kit that bundles the light with a smart plug.

What to pay for and what to skip

Pay for numbers you can check. The most useful spec is PPFD at stated distances, because brightness drops quickly as the light moves away. House Plant Journal measured the Soltech Aspect Gen 2 at 683 µmol at 12 inches, 167 at 24 inches and 46 at 48 inches. Doubling the distance cut the light by roughly three quarters. A single PPFD figure with no distance tells you little. Bob Vila's reviewers also say to compare actual power draw, not 'equivalent' wattage, and to compare PPFD only at the same distance.

Next, pay for a light that is easy to adjust. A dimmer, a height you can change, and a coverage area that matches your plants matter more than a bigger wattage number. Bob Vila's reviewers suggest measuring the area your plants take up and buying a light rated to cover it.

• Worth paying for: published PPFD at several distances, real power draw in watts, a dimmer, adjustable height or hanging cable, a timer that runs as long as you need

• Usually skip: red-blue lights for living spaces, unexplained 'equivalent' wattage claims, PPFD figures with no distance

• Usually skip for houseplants: big vegetable panels. Bob Vila's rule of thumb of 32 to 80 watts per square foot is aimed at growing food. A panel like the Mars Hydro TS1000, measured at 743 µmol at 18 inches, delivers many times the 40–80 µmol most foliage plants need

Common mistakes

Hanging the light too high is the most common problem. Because light drops so fast with distance, a fixture that is strong at 12 inches can be marginal at 3 or 4 feet. Measure at the top leaves, not at the shelf.

Hanging it too close is the opposite mistake. Bob Vila's reviewers advise keeping LEDs generally at least 12 inches above plants to avoid leaf burn. Fluorescent tubes are a different case: Iowa State suggests placing them within 4 to 6 inches of the plants because their output falls off with distance. Follow the guidance for your type of fixture.

• Leaving lights on 24 hours a day; the extension sources cap it at 16

• Trusting a phone app instead of a meter to judge light levels

• Buying a single-plant clip or ring light for a whole shelf (Bob Vila lists the Lordem ring light at about 0.5 sq ft of coverage)

• Guessing instead of measuring; House Plant Journal's advice is 'don't guess with light'

• Ignoring setup: Bob Vila's reviewers flag loose power cords as a trip hazard and note that the Lordem stake wobbles in pots smaller than 6 inches

Price tiers

Entry level: screw-in bulbs and small single-plant lights. The GE 9W Balanced Light grow bulb fits a standard lamp socket. Bob Vila lists it at about 16 µmol/s output and a 25,000-hour rated life, with no dimming or timer. Ring and clip lights like the Lordem add built-in timers and brightness levels but cover only one plant. Lights like these suit one or two plants that need extra light in a dim spot.

Mid range: bar and panel lights. The Spider Farmer SF600 was listed on the maker's site at around $66 on sale in November 2026 (regular price $79.99). The listing gives 72 watts, 2.3 µmol/J efficiency, 2×4 ft coverage and a 5-year warranty. It has no dimmer or built-in timer. Lights in this range suit a shelf or plant stand, but they look like equipment.

Premium: design pendants. The Soltech Aspect Gen 2 was listed at Bloomscape at around $200 in November 2026. Bloomscape lists 36 watts, a built-in dimmer, an 18-foot cord and a 90,000-hour rating. House Plant Journal, which discloses a paid partnership and affiliate link with Soltech, reports a built-in timer and a high color rendering index. The extra cost buys looks and light that is pleasant to live with, not more plant growth per dollar.

Sources

• Lighting | Houseplants | Illinois Extension
• Will standard fluorescent bulbs provide sufficient light for houseplants? (Iowa State University Yard and Garden)
• Grow Light Strength Recommendations by Plant (House Plant Journal)
• Review: Soltech Aspect Gen2 (House Plant Journal)
• The Best LED Grow Lights for Thriving Indoor Plants, Tested (Bob Vila)
• Best Grow Lights For Houseplants (Gardener's Supply)
• Aspect Gen 2 LED Growlight (Bloomscape)
• Spider Farmer SF600 Vegetable LED Grow Lights