Jane: I have a 600 W metal halide bulb about 18-24 inches above some of my seedlings in the greenhouse. I've never had any problems with burning or apparent damage from too much light. My main problem is not enough light on Lachenalias and other SA bulbs. I have my bulb go on at sunset and off at around 11 PM. Arnold On 11/05/15, Jane McGary wrote: My new lamps are metal halide. I have them fairly high above the plants, but I will take Kipp's advice and stretch a shade cloth between the light and the plants. Many of the plants are young seedlings and thus more sensitive to burning. Jane McGary On 11/5/2015 11:28 AM, Kipp McMichael wrote: > Jane, > > I assume your new fixtures are a metal halide or high pressure sodium. These are indeed strong lights and can burn even full sun-loving plants. I would suggest shading with cloth or placing more sensitive plants outside the "cone" of light directly beneath the fixtures. > Just to note: If you lights are still fluorescents then they are unlikely to burn anything unless the bulbs are within inches of the plants. > -|<ipp >