LED vs. HPS Light Intensity -- What You Should Know

I have been asked in an E-mail to use a light meter from HTGSupply.com to compare a 90W UFO LED to a 600 W HPS

What you should know is that using a light meter is not the best way to compare these two lights.  The benefit of  LED's is that they emits a very specific wavelenght of each light, this is why there are individual colors of LED lights, because each LED emits such a narrow range of light it looks like a single color to our eyes.  An HPS (or MH) on the other hand, emits a greater light intensity.  The light meter will show a higher output of light from the HPS but the problem is that not all the light is available for plants to use during photosynthesis.  Translation, a lot of the light is wasted and a lot of the energy to create that wasted light results in heat generation too.  This is why LED's CAN BE more efficient, they use less energy and only emit light that plants need to do photosynthesis.  The reason I say CAN BE in caps is because it is possible to make an LED that is less expensive, but it emits light that is NOT in the optimal wavelenght for photosynthesis.  This means the light will not promote good plant growth.  The reason this is a problem is that the pigments that absorbs light in plants for photosynthesis are different than the three pigments we have in our eyes that absorb light and let us see color.  Translation, what we see as red is not necessarily the best 'red' that plants need to conduct photosynthesize.  I know that the Tri-Band technology from HTGSupply.com is tested and I personally have grown numerous plant species from seed to flowering under it.

Good Growing
Dr. E.R. Myers


Using a screen or SCROG – re-revisited

An acquaintance of mine did a sort of scientific experiment. He used the same light but different plants and a different area to compare the SCROG method with a traditional grow method where plants are not tied down.
First, he grew using the SCROG method, where he grew multiple plants in 1-2 gallon pots under a 400W HPS. We wanted to test how well the plants would grow in a small space.  He kept the plants at three feet (The wire was 2 feet 8 inches off the floor) with the HPS two feet above the tops. This was a little close as some plants showed signs of heat stress.  (I'd recomed an LED next time) He grew the same variety of plants but grew less plants in larger containers (all in 2 gallon pots). The reasoning for the difference was that he figured with the SCROG method, it would be better to have more plants; with more plant tops to tie onto the fence (He also prefers fencing with 2x3 inch holes vs. chicken wire). He said his yield was greater with fewer big plants that were allowed to grow without being tied down. As I said, this is not a real scientific experiment, because he used different containers. You want only one factor or variable to be different when comparing groups. So, in this case we cannot say for sure if the increased yield was due to larger plants/pots or to not being restrained and tied to a screen. I thought some of you might like to atleast have this information.
As always if anyone has any information or further questions please contact me via E-mail

Good Growing,
Dr. E. R. Myers


E-mail - Ventilation and CO2 Use

Hello. I have answered the first questions about CO2 and plant growth, I had to ask Perry a manager at HTGSupply for the question about the ducting etc. He is much more knowledgable than me about equipment use. His answer is below mine in purple.

Dr. Myers,
Upon reading your article, "Information on CO2 Ventilation for the Growing Season," several answers of mine were answered; however, some of questions remained unanswered.
First- You were clear on the amount of CO2 to release, but I would also like to know:
1. How often should I release it if I have no meter (5 min/hr)?
If you see Perry's comment below, you would be wise to invest in a meter. You will end up using more CO2 if you do not, which means the meter will pay for itself in CO2 savings. This really is the only solution. If you don't know how much CO2 is in the grow area, and how much is being released (time/hr is not going to give you these numbers) no one will be able to tell you if you have enough CO2. You could start out at 5min / hr until you get a meter.
2. At what point during the grow cycles are critical?
a)Is it optimal to provide CO2 from seedling to harvest?

Great question!  CO2 is needed for photosynthesis and studies have shown that when the CO2 rate goes up so does photosynthesis. So, I think you'd have the best results by providing CO2 to your plants from seedling to harvest.

Second: I now have a question about ventilation:
1. With the provided 4" ports on the HTG small grow tent; how should I configure, and what parts are needed for proper ventilation? I will have the 4" carbon filter/fan combo, but that is it. Also, My reflector wing does not have ports of any sort. (socket on one end and open on the other)

If you are utilizing a CO2 injector, then it will be best to use the fan and filter combo as a means to cool the lamp, whilst minimizing the exchange of air inside the tent! This means that you will need a Air Cooled reflector! This is a reflector that has a housing surrounding the lamp with a piece of glass underneath and flanges on both ends to connect ducting/fans , thus making heat removal possible. Or a glass Cooltube type reflector.
The Reflector you described sounds like a standard Lightwing or Waxwing reflector, also called a Batwing, which is not air coolable.
Fan and Filter will need to be "run through" the tent and consequently through the reflector at the same time. A total of 4 flanges will be needed, two per port sandwiching the tent material between to create a double flanged port on both sides. This allows you to connect the air coolable reflector to ducting and the flanges on the inside, while at the same time providing a mountable surface on the outer side to attach ducting to the fan and filter. Essentially the filter will be on one side of the tent, connected to the tent with ducting, then ducted to the reflector, then to the other flange, then finally back out to the fan. This completely segregates the air going threw all this from the tent! Complete heat removal, without affecting the CO2 levels inside the tent!
The Fan and Filter Combos can be used to cool the tent. However this will affect CO2 levels and I strongly recommend using a control unit! Essentially the filter is hung from the tent framework from the top. The ducting then runs to the fan which pulls air from the tent via the filter and exhausts it to a outside(of tent) area. This will clear the tent of CO2 within a minute or two!
Operating a CO2 injection system without a Controller unit is hard! Plus may end up costing more in the long run. Do a google search for "Using a CO2 injection system without a Controller". There are many "hands on" responses from a variety of forums! All mention that typically using a controller will reduce the need to replace CO2 tanks by half. So a tank that will last you 2 weeks controlling it with a timer will last 4 weeks if controlled by an actual CO level controller. Within a short amount of time, replacing spent tanks will cost you more than a control unit does!
Thanks and have a great day!


A Haiku on 12-12-12

Growing plants is fun

Light, Water and C O 2

Harvest and enjoy!


300 W LED vs. 400 W HPS

I got an E-mail from a reader that asked me not to use her name. She had been using a 400W HPS for many years, but decided to give LED’s a try, for the energy conservation, which is good for the environment, but the fact that LED’s don’t need new bulbs every 2 years, also means less resources are used, another financial and environmental benefit. She told me that she harvested a little bit MORE using the 300 W Tri-Band sold by HTGSupply. More importantly, she said she did not have to tie down the plants which used to grow overly tall and lanky when first put under the HPS. (Read my post on HPS and flowering) I love getting these E-mail’s as well as questions about growing. I enjoy growing and helping others and we can all learn from each other. If anyone else has made the switch from HPS to LED, let me know the results.  In my 2010 post comparing LED and HPS,  I suggested to use an HPS over LED for flowering, after using the LED's from HTGSupply, I now think LED's are comparable even during flowering

Good Growing,
Dr. E.R. Myers


Drying Herbs - Pictorial

This is one of three sections that comes with the Dry Net Ultra

Air drying herbs can be used to preserve all types of herbs, unlike freezing herbs which is only suitable for certain high moisture types. Many people enjoy their herbs year round by drying their herbs and keeping them in jars or airtight containers.

A simple method of air drying is to hang the plants with leaves/flowers still attached to the stems and upside down in a closet. This is how I dry garlic in the fall. For most other things, like the hops I grow to brew beer, I use the dry net.

Air drying is great because it does not cost a dime. I have happily been using the dry net for a few years, and I really like it. Simply spread the cleaned leaves or flowers one layer thick on a section of the dry net. This allows proper air flow, I have recommended to turn the plant material over each day to ensure even drying. It is best to do this process indoors away from intense heat and light which would cause the herbs to lose greater amounts of flavor. The dry nets fit inside most grow tents, so once you are done growing, you can use the grow tent to dry your herbs.

It took about a week to dry these hops in my spare room.  The temperature was about 68F and humidity ranged from 40-60%.   I kept the ceiling fan on 24/7 to promote moderate airflow.

Once your herbs are dried, you can store them whole (such as I have done above) or crumble the herbs (such as oregano) before placing them in an airtight container such as a glass jar. I put these hops in plastic bags and have them in the freezer.  Hops are best fresh, so I will be using these to add flavor on the next few batches of beer.
Good Growing,
Dr. E.R. Myers