Continuous vs Spiked Spectrum in LED Grow Lights

What continuous and spiked mean on a listing

A grow light listing may describe its output as 'continuous spectrum' or 'spiked spectrum', or it may use neither phrase and simply say 'full spectrum'. All three are labels for the shape of the light's output across the visible range and the wavelengths just beyond it. They are not measurements of how much light a plant receives.

A continuous spectrum label describes a smooth, unbroken spread of wavelengths. Most listings that use it also say 'full spectrum' or name white LEDs. A spiked spectrum label describes output concentrated in specific peaks, usually named as red and blue, and sometimes as a single wavelength such as 660nm red.

The shape of the spectrum is one detail of a light, and it appears in a title only as a phrase. The actual spectrum chart, if the maker publishes one, is on the maker's page and in the manual for the model. Read both next to the listing before you decide.

Continuous spectrum as a listing term

When a title says 'continuous spectrum' or 'full spectrum', the seller is describing a spread of wavelengths that covers the visible range without large gaps. On many listings this labels white-LED fixtures, and the title may add a Kelvin value such as 3000K or 5000K. Kelvin is a color temperature label, not a spectrum chart.

The phrase does not tell you intensity. A full-spectrum label says nothing about how much light reaches a plant, how far the light should hang, or how long it should stay on. Those questions are answered by the maker's page and manual, not by the listing phrase.

Related reading on this site: full spectrum as a listing term and white LED versus blurple.

Spiked spectrum as a listing term

A 'spiked spectrum' or 'targeted wavelengths' title names specific peaks, most often red and blue. An older style fixture, sometimes called blurple, concentrates its output in these two peaks and may not carry a full-spectrum label. See blue versus red light for the difference between the two peak names.

A title may also name a particular wavelength, such as 660nm red or 730nm far red. These names describe where a peak sits, not its height. The height of a peak appears on a spectrum chart that the maker publishes separately.

For a reader, a spiked label is a clue about the light's design, not a promise about plant growth. Compare it with the watts, coverage and controls named in the title.

How to read the phrase on a listing

The table below matches common listing phrases to their plain meaning. It is a reading guide, not a measurement.

When a listing mixes phrases, such as 'full spectrum with deep red', read the maker's page to see what the title compresses into a few words.

Which shape fits which job

For a shelf of houseplants, a windowsill of herbs, or a desk plant, listings labeled full spectrum or continuous are the common starting point. The guides for panel lights, strips and bulbs take these labels as a starting point.

For a grow tent, a quantum board or bar light listing may name specific wavelengths; if the title says spiked or names red and blue peaks, read the maker's page to see the chart.

The spectrum phrase is one part of the title. Pair it with the stated watts, coverage, dimmer and timer before you compare two lights. A dimmable light with a timer gives you control over the schedule that the spectrum phrase alone cannot.

Where the real spectrum is stated

The listing title gives you a label; the maker's page and the manual give the spectrum chart, the diode names and the wavelength peaks. The DesignLights horticultural lighting program publishes qualified products lists and verifies stated performance claims for listed fixtures, which is a place to read a maker's stated claims alongside the maker's page.

The University of Minnesota Extension lighting guide explains light levels for indoor plants and starting seeds in general terms. Read it next to the maker's page to put a spectrum label in context.

The catalog used for the guides on this site reads stated details such as light type, watts, coverage and controls. It does not read spectrum charts, so for a spectrum question the maker's page and manual come first.

What the catalog cannot tell you

PPFD, PAR and DLI are terms that describe light in photon terms, and listings rarely state them. What those terms mean is explained separately; when a maker publishes them, they appear on the maker's page, not in the title.

The catalog also does not state hanging height, hours of light per day, distance from plants or efficiency. For any of these, read the maker's manual and page.

When you mount any light, the maker's manual and local electrical rules come first.

What to pick for your job

Questions

Is continuous spectrum the same as full spectrum?

On listings the two phrases carry the same idea: a smooth spread of wavelengths across the visible range. The maker's page is where the actual chart appears.

Does a spiked spectrum light work for houseplants?

A spiked label describes the shape of the output, not whether it can light a houseplant. Compare the stated watts and coverage and read the maker's page before deciding. The houseplant guides start from full-spectrum labels.

Where do I find the real spectrum chart?

On the maker's page and in the manual for the model. A listing title compresses the spectrum into a few words such as 'full spectrum' or 'red and blue'.

Which is better for a tent grower?

Neither label is better by itself. A tent grower reads the spectrum chart on the maker's page alongside the stated watts, coverage and controls.

Why do listings avoid PPFD numbers for spectrum?

PPFD and similar terms describe how much light arrives at a plant, and makers usually publish them on a separate data sheet or in the manual, not in the listing title.