Houseplant hobbyists may be confused when they start seeing grow lights defined as 5000K or 6500K.
These numbers refer to the kelvin color temperature of light. When using a grow light for indoor plants, the goal is to recreate the same light that the plants would receive from the sun outside.
What’s the difference between 5000K and 6500K? Both color temperatures are similar to natural sunlight. However, 5000K is more similar to morning or evening sunlight while 6500K mimics midday sunlight. In general, plants can survive within the color temperature range of 2700K-7000K, so both 5000K and 6500K are within an acceptable range.
There is a lot of debate amongst horticulturists and home gardeners around if there is any difference in using one over the other.
Oftentimes, a gardener finds the ideal color temperature through trial and error.
Understanding Color Temperature for Plants
Color temperature is the color radiated by a light source. The best example of this is lightbulbs labeled as “cool white” or “warm white.”
Cool white has blue tones and has a higher number on the Kelvin scale. Warm white has red tones and has a lower number on the Kelvin scale. The kelvin color temperature spectrum ranges from 0-10,000K.
Historically, horticulturists have said that light sources higher on the Kelvin scale (blue light) are better for vegetative growth.
On the other end of the spectrum, red light is said to be better for flowering plants.
Modern light bulbs come in different varieties (LED vs. CFL) and hundreds of different brands.
Testing has shown that there can be a large difference in the amount of red or blue light emitted from different bulbs. Therefore, it is no longer as simple as using warm lights for flowers and cool lights for vegetables.
5000K vs. 6500K for Plants
Both of these values are in the range of daylight, so they are both considered adequate for plant growth.
Depending on the plants you are growing, the goal for those plants (ex: foliage vs. flowers), and the type of lightbulb you are using, one or both values may be appropriate for your plants.
Understanding the Difference Between 5000K and 6500K
5000K and 6500K are not that far apart on the Kelvin scale. Therefore, it can be hard to see the difference with the naked eye.
Since 5000K is the lower value, it has more warm tones. This is similar to sunrise or sunset. Since 6500K has more blue tones, it is similar to mid-day sun.
What Plants Do Better With 5000K?
Most houseplants do not want full sun. They are tropical plants that evolved in partial shade or filtered light situations.
Therefore, most houseplants, and especially those that want shade or partial shade, will do better under 5000K light.
What Plants Do Better With 6500K?
Plants that need full sun and are typically grown outdoors will do better with 6500K light. This is a closer simulation of the bright sunlight that these plants crave.
Some varieties of houseplants that enjoy more sunlight will also thrive under 6500K.
Is 6500K Brighter Than 5000K?
Brightness is different than color temperature. Brightness is measured in lumens, and the amount will vary between bulb brands. Check the packaging on the bulb to see how bright it is.
Since 6500K is a cooler color temperature, it can often appear to be brighter than the warm-toned 5000K. This is just an optical illusion though.
Is 5000K Full Spectrum?
Yes, 5000K to 6500K is considered full spectrum on the Kelvin color temperature scale because all light colors are emitted.
However, since this value is in the middle of the scale, our eyes will not observe a warmth or coolness to the color of the light.
Does 5000K Look Different Than 6500K?
A skilled horticulturist who is well-versed in grow lights may be able to see the difference between 5000K and 6500K.
However, most people cannot tell the difference because these two values are similar in the color temperature that they emit.
What Color LED Is Best for Plants?
Plants require both red and blue light for optimal growth. Since colors are at opposite ends of the spectrum, it is important to use a full-spectrum LED light.
Yellow and green lights are found in the middle of the spectrum, but they are not very important for plant growth.
How Many Hours Should Plants Be Under a Grow Light?
Grow lights should be on for 8 hours per day on average. The time will vary depending on the plant and its sunlight requirements.
Shade or partial-shade plants don’t need as much time under a grow light, or they can be housed under a less-powerful light. Sun-loving plants may need a grow light for up to 16 hours per day.
Wrapping It Up
If you are looking for a grow light for your houseplants, don’t worry too much about choosing between 5000K and 6500K.
While finicky plants may have a preference one way or another, the majority of houseplants will do well under either light.