E-mail Ques. Best light to use if you only use one

Hi Dr. Myers
Question: For vegetative stage, is it Ok to just use a HPS 400 watt
light instead of T5 fluorescents? Do the plants need this blue wavelength? It would just be easier to have 1 light for the whole vegetative and flowering phases. Any suggestions?


It is ok to use an HPS, for vegetative, I am doing it for my summer garden right now. A 400 HPS does have enough blue light, it is just that the red/yellow are in the extreme. The problems you may face are 1) it may get hot and 2) There is an excess of red/yellow to blue light with an HPS. Lucky for you both problems may cause plants to grow tall and fall over. I say lucky becasue all you need to do is create a light wind with a fan on the seedlings and plants, and this should help keep the plants shorter.
Even with a fan, I have had some plants get really stretched growing under HPS, I just bend and tie down the plant tops with pipe cleaners or twist ties and that kept the plants from getting too tall because 1)I physically lowered the plant and 2) when you bend the top of a plant supresion hormones made in the top can’t get to the rest of the plant cells telling the branches not to grow. This means the plant will get bushy rather than tall. Some people suggest cutting the tops to get a more bushy plant I prefer to tie down the plants, it has the same effect with less stress to the plant and you get a flower on the main stem which are often the biggest and best...

A T-5 or any fluro. would be better for the seedlings, but if you have to go with one light from start to finish, I say use the HPS and a fan and you will get the best bang for your buck.

Good Growing,

Dr. E. R. Myers

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