You can use a common household lamp to provide light for your plants, but the results will likely be limited compared to using a dedicated grow light. Success depends entirely on the specific type of bulb you use and how you position it, as not all light sources are equal for plant growth. Standard lamps can support low-light foliage plants or help seedlings survive, but they rarely provide the intensity and specific light composition necessary for flowering or fruiting.
Understanding Plant Light Requirements
Plants use light energy to power photosynthesis, a process that relies on specific wavelengths, not just overall brightness. The light spectrum that drives growth is known as Photosynthetically Active Radiation (PAR), spanning the 400 to 700 nanometer range of visible light. The amount of usable light reaching the plant is measured by Photosynthetic Photon Flux Density (PPFD), which is a much better indicator of a light source’s effectiveness than standard lumens.
The color, or wavelength, of the light significantly impacts development. Blue light (400–500 nm) is primarily responsible for vegetative growth, encouraging compact, leafy plants and strong stems. Red light (600–700 nm) is important for chlorophyll synthesis and plays a major role in triggering flowering and fruiting stages. A successful lamp setup must provide an adequate balance of these wavelengths to support healthy growth.
Analyzing Common Household Light Sources
Most traditional household bulbs were designed for human vision, not plant biology, making their spectrum and intensity often inadequate for robust growth. Incandescent and halogen bulbs are the least suitable options for supporting plants. They emit a spectrum heavily dominated by red and far-red light, while producing very little of the blue light necessary for stocky vegetative growth. These bulbs release most of their energy as heat, which can easily scorch leaves if the lamp is placed too close to the plant.
Fluorescent tubes and compact fluorescent lamps (CFLs) produce less heat and a broader spectrum of light. “Cool white” fluorescent bulbs work reasonably well for vegetative growth, as they contain a higher percentage of the blue light spectrum. However, fluorescent lights have low light intensity, meaning they must be positioned very close to the plant canopy to be effective, usually within 6 to 12 inches.
Modern, non-specialized household LED bulbs are highly energy-efficient and generate very little heat, but their effectiveness for plants varies widely because they are engineered for human vision, not to maximize PAR output. They often lack the concentrated red and blue wavelengths found in dedicated LED grow lights, resulting in low PPFD values. While a household LED can sustain a low-light houseplant, it will not provide the intensity or tailored spectrum to support high-demand plants like herbs or fruiting vegetables.
Optimizing Distance and Duration
The most important factor to control when using a non-specialized lamp is the distance between the bulb and the plant. Light intensity decreases as the distance from the source increases, following the inverse square law. If you double the distance, the light intensity reaching the plant drops to one-quarter of the original strength.
Because household bulbs are low intensity, they must be positioned closer to the plant than powerful grow lights to deliver sufficient PPFD. For low-heat sources like fluorescent or standard LED bulbs, a distance of 6 to 12 inches above the plant canopy is necessary. To check for heat stress, hold your hand at the level of the plant leaves; if the heat feels uncomfortable after a few seconds, the light is too close.
The duration of light exposure, or photoperiod, is critical. Most plants require between 14 and 16 hours of light per day for optimal vegetative growth, while some need 12 hours of uninterrupted darkness to trigger the flowering phase. A common sign that your lamp is too far away is “etiolation,” where the plant stretches and becomes spindly. Conversely, bleached, scorched, or curled leaves indicate that the light is too intense or too close, causing light burn.