Single Best light revisited

In a previous post on June 29th  I answered an E-mail asking if it was possible to use only an HPS for growing plants indoors. While my answer has not changed, if you can only use one light I recommend an HPS. I’d like to add to this with some new information.  I would also like to add I continually review and may add links etc. to old posts, so any comments or questions about old posts are ALWAYS welcome.
While I still say that if you must use only one light, the best is an HPS. I would like to expand on that. I always have started seeds with a fluorescent light, but this semester, I started some under the HPS. I noticed the seedlings growing very long stems and most seemed as if they would soon fall over.  After one week of this, I moved these tall little seedlings which were basically a stem with cotyledons and put them under a fluorescent light. They immediately stopped growing in stem length and the true leaves began to grow instead.

The reason my seedlings stretched was partially genetic (some plants stretch more than others under an HPS) but I did not have a fan on the seedlings which might have helped cut down the stem elongation. I think that all seedlings should be started under fluorescent lights. A T5-HO is the best, but many of you have mentioned monetary constraints. You could go to a local hardware store and buy a two tube 4 foot fluorescent ballast with some cool white bulbs for around 20$. This won’t be enough light for most plants to finish growing but will give you some really nice sturdy, stout and bushy seedlings. Once the plants are a few inches tall you can put them under an HPS.

So, if you only can only use or buy one light, I still recommend an HPS and a fan, but for a few dollars you can get a cheap fluorescent light and use it for the first 2-4 weeks to make sure your plants start off growing strong, not long.

Good Growing
Dr. E.R. Myers


Anonymous said...

There seems to be many different types of HPS bulbs, many saying they have more blue spectrum than others and that that is needed for proper plant growth (as we all know). What hps bulb type or brand do you recommend? Also, wouldn't a dual arc bulb (hps & mh) be really the best bulb to grow under, if you can only have one? Thanks!

Dr. E.R.Myers said...

There are conversion lamps, but they are not near as bright as standard HPS of the same wattage. A 1000 watt Dual Arc bulb is essentially a 600w HPS arc tube and a 400w MH arc tube. The 600w HPS emits 90,000 lumens, the 400w MH 36,000 lumens TOTAL lumens =
126,000 whereas a straight up 1000w HPS emits 140,000 - 150,000 lumens (higher lumens = higher yields).
Spectrally Enhanced (30% more blue) HIGH OUTPUT HPS light is the BEST for Flowering. For a beginner on a budget, the 400 watt HPS is relatively cheap to purchase and operate and the heat is more manageable than the higher wattage systems. I think HTGSupply.com’s 400w HPS is the BEST beginner light on the market and the sales back that up it is their most popular light. The Digital 600w HPS for $199.95 is fast approaching the sales of the 400w HPS. This light can grow more plants but it also emits almost twice the light as the 400w HPS but only uses about 50% more electricity. Electric bills are higher and heat can be more of an issue but overall production is substantially better.