Researchers at several universities have proposed a standard lamp label specifically geared to horticultural applications. From Urban AG News, which has the story:

The label includes the efficacy (output of photosynthetically active radiation per unit of electric power consumed measured in micromoles per joule (μmol/J), conversion efficiency, photon flux output in key wavebands in 100 nanometer (nm) increments across the 300-900 nm waveband, the phytochrome photostationary state, and graphs of the normalized photon flux across the 300‐900 nm waveband, as well as the light intensity distribution at a specific distance from the light source.

“Any time a consumer buys a light bulb there is a label on it that was designed and promoted by the Department of Energy,” said agricultural engineer A.J. Both, who is associate extension specialist at Rutgers University. “This was our starting point. In the case of horticultural lamps, the end users have much different interests than consumers who are buying light bulbs for their homes and businesses. The university researchers that worked on this label had to decide what was the important information that would be useful for greenhouse growers and other controlled environment users. This is how we came up with this particular label. Our intention is that the label can be used for all light sources used for horticultural applications.”

Read the article here. The proposed label is shown below: