E-mail - Burnt Seedlings and Proper HPS Height

I just purchased a grow system from htgsupply.com --it was the hps 400w. I put my plants in my area to grow and they got burned by the light. I have plenty of ventilation for them. How far should I have the light from the plants. I just planted my seeds

For seedlings a 400 HPS should be 2-3 feet above the plants. With larger plants with good ventilation you can have the light 1-2 feet above. Young plants in small containers will need to be protected from drying out quickly under the HPS. You should think about a thermometer with a minimum / maximum setting. If your plants are burned the temperature probably was above 100F. If it was not it might be too much fertilizer or a disease...

I have recommended a few times on the blog that seedlings are better started under fluorescents’. The T-5 high output HTGSupply.com sells are awesome, you can grow bushy, sturdy green plants a foot tall or more easily but I know they are not cheap. If you only have a few bucks get a double bulb 4 foot fluorescent light from the hardware store with cool white bulbs. With these cheap fluorescents’ keep the bulbs 1 inch from the tops of the plants and you may be able to grow plants 6 inches that are green, bushy, sturdy, and will be ready for the HPS.
Good Growing,
Dr. E.R. Myers


E-mail- Best 2nd Light and Stem Elongation

I got a question about HID lighting. Currently I have a 600w hps and would like to upgrade to another 600w. I am using a Digi ballast, and would like to figure out whether or not to use a HPS/HPS combo for flowering or HPS/MH. I know MH aren’t as lumen efficient as HPS bulbs are but I also have been doing a lot of reading on how plants don’t really care about the lumens as much as the PAR watts. So before I go buy another 600w combo I’d like to figure out whether or not I'd be in my best interest to have a more mixed spectrum or just a enhanced spectrum HPS like I have now. Lastly id like to say I’m going for the maximum yield.

Hello and thank you for the question.
As usual the answer is it depends… If you are seeing any problems with stem elongation, (you are tying plants down so they don’t grow as tall, or propping them up because they are tall and lanky) I think you need an MH, or an hps/mh combo. You won’t have the light output as with an HPS but you will increase yields over your current set up for sure. If you add another hps you will have more stem elongation than you do now, the yellow/red combo so loved for flowering also increases stem elongation especially when plants are in a vegetative state. The more blue light output of an MH causes plants to have shorter stems and would actually decrease stem elongation compared to what you have now I’d imagine.

If you do not see stem elongation with your current set up I would add another hps. I say this because the yellow/red light of an HPS increases the flowering response more than the widespread light output of an MH. If you are looking for flower/fruit yield I would also go for the two HPS, again as long as you are not having a problem with stem elongation.

I think you have the right idea about PAR. An MH may have a slightly higher PAR, but the hps has more PAR in the light that induces flowering. Most other light colors (wavelengths) are given off in sufficient quantities by an HPS so a second HPS will not be a limiting factor.  Yet another reason I’d recommend an HPS, an MH bulb can lose up to 50% of its output in a year. It will take an HPS 2-3 years before it has lost 50% of its initial output. That is also something to consider, you will be buying replacement bulbs for an MH yearly if you are looking at yield.

I hope that helps, feel free to drop me a line and let me know what decision you made and how it worked out.

Good growing
Dr. E.R. Myers


E-mail - MH bulbs - Plant Growth and Kelvin

I am ready to replace my old 1000 watt metal halide bulbs. I do not own a hps light and want to run a full spectrum bulb for vegetative growth and  flowering. I am familiar with the new dual arc bulbs but they are not in my budget. I do not want stem elongation that I may get with a red spectrum hps in vegetative stages, but obviously need it for flowering. It is my understanding that a 6500k bulb would be best? Please help me in deciding which bulb is best suitable for good vegetative growth without stem elongation and suitable in the flowering stages also, If I have to sacrifice fast veg. growth and shorter plants for better flowers by using a 3000k lamp I will. Any and all help is appreciated.
Thank you!

I sent your E-mail to Sales@HTGSupply.com for a specific recommendation since I am not as familiar with specific bulbs / equipment.
I can answer your questions regarding light and plant growth however. You are correct in that a lower Kelvin rating means there is more red and yellow which will promote flowering but also means stem elongation. I have always used an HPS, but sometimes I use a MH conversion bulb during vegetative. If you ever get a new light, I usually recommend an HPS but since you don't have one....

6500K MH is the BEST spectrum for vegetative growth. It is a "blue" or "cool" spectrum bulb and it really grows compact, green plants. A lot of growers use this bulb for all stages of growth. The 3000K bulb is an MH bulb and the light output is not so great if you compare it to the same wattage HPS which typically has about a 2200K spectrum which is not too far off 3000K (one reason I use HPS).  However with an MH, if flowering is your main goal, go with the lower K (maybe just during flowering stage if you can get two bulbs?). You may have some stem elongation which you can correct by bending the plant tops which will make the plants more bushy, or you can have a fan blowing directly on the plants (gently) which will cause the plants to have shorter thicker stems. I do not think you will have as much of a problem with stem elongation with a MH of any type as you would with a HPS. I hope this helps, I'd like to hear from you later about how things worked out.

Good growing
Dr. E.R. Myers

p.s. These are generalities but basically an overcast Sky is 6500K. An incandescent light bulb is 2700K and is yellowish-white. The warm-white fluorescents are about 2700 K and are popular for flowering. Neutral-white fluorescents have 3000 K or 3500 K. Cool-white fluorescents are my bulb of choice for growing young plants and are 4100 K


E-mail - How Much CO2 to Add - Plant Processing of CO2

Hi I read your article on co2 enrichment. Very informative! I do have one question though. How fast do plants process the co2? What I mean is, how long do I need to leave the fans off after I add co2 to the grow room? I have a small area, 6x6. My budget is low, so I am using a poor man's approach and just empting 12 gram co2 cartridges over the plants. Since the amount is so small, will the plants process it in 15-30 minutes? Also, if I am able to say purchase one of the co2 enrichment packages from HTG, how long would I need to leave the fans off? Thank you for your time.

Glad to hear people are still checking out some of my old articles. To start with, I should say that the CO2 in the atmosphere has a concentration from 0.03 to 0.04 %. However, it is found that increases to CO2 to 0.1% of carbon dioxide in the atmosphere increases the rate of photosynthesis significantly. This was tested indoors with enclosed chambers where plants are grown under controlled conditions. Crops like tomatoes, lettuce etc. were successfully grown in the chambers and were found to be bigger and better-yielding than their counterparts growing in natural carbon dixoide conditions. I have read your rate of photosynthesis increases if you increase carbon  dixoide to 0.2%.( that is 2000 ppm)   After that I have not seen any studies showing improved growth.

As it said in my article you can figure out the ppm in your room with a bit of basic math and I would try to get your ppm up to 0.2% or 2000 ppm if you can.  Since the use of CO2 is dependent on many variables here are some things to keep in mind: Plants will use more CO2 the higher their rate of photosynthesis. If you use a HID, your plants will use more CO2 than with a fluorescent light fixture. Also, the bigger your plants are, the more CO2 they can use. So, the more light you give the plants and the bigger they are the faster they will use up the CO2. For best results you need to add the CO2 above the plants in a sealed room with no ventilation (fans are ok just no exhaust fans) and let the plants be exposed to the high CO2 concentration for an extended time. They need to soak in the CO2 through tiny holes (called stomata) in their leaves.

How are you adding the CO2? “manually”, I am not exactly sure what the C02 cartridges are? If you are doing this with the door open, you may not get improved results as the CO2 will diffuse out the open door.

As I mentioned, the ideal system is to have the CO2 released when you are not in the room, and the door is closed. You should try to seal the room to make it air tight. This way, the plants will use as much of the CO2 as possible before it leaves the room. Also, if the room is sealed well you should leave a light fan on, this will help mix the CO2 which will have a tendency to sink to the bottom of the room. If you have an exhaust fan, you could shut the fan off during the night cycle, when there is less heat and a need for exhaust, and add the CO2 then. This will give your plants 6-12 hours of exposure (depending on what light cycle you are using) and that way you can be sure your plants are using all the CO2 they can. I understand you are on a budget, but a CO2 system with a timer releasing the gas above the plants in a sealed room is really the best way to increase your growth and yield with CO2, I have read studies that show a doubling of yields just by increasing CO2.

I do want to end by saying that any CO2 you add should help the plants grow better, so although I can't tell you exactly how many grams you should add, if you add any it is better than nothing. A time release system would be optimal, and then using my article you could add enough CO2 to the room to see big results, but anything you do to improve you growth is good.

I hope this helps, good growing,
Dr. E.R.Myers


E-mail -- Drought Proof Your Outside Plants

Hello Dr. Myers,
I was reading an old post/ article with your question to the public about how to keep up your plants that you can only tend to once a month or so.  I have a few suggestions that you may already know. First, to the best of my knowledge soil conditioned with Humic acid will retain more moisture naturally. I have found this to be true and also have found that plants put in humic conditioned soil tend to take root in the soil faster and bounce back from transplant shock faster as well. I also know that the carbon in the humic acid will feed the microbes in the soil. I am a big fan of the beneficial fungi and bacteria too because they will make the plant more drought resistant. These are all of the natural methods I know of to make plants more drought resistant but one way unnaturally is to add polymers like Soil Moist. I'm not sure if its on the HTGSupply.com web site or not but I have bought it at the Cranberry store and it will retain moisture considerably and slowly release it in the soil over time. This takes a good eye so you don't flood your plants with water for too long so it will be the type of thing that takes some getting used to but it works great.

Thank you CJ for sharing your experiences to help make us all good growers.
Dr. E.R. Myers


E-mail -- pollination

Happy 4th of July!

 I will be posting many past E-mail's this month.  I am always happy to get grow questions!!!  Please write if any topic is not covered or you want more details about topics you read in past blog posts.

Hi Dr. Myers

You have answered questions from me in the past and I do have another one. In addition to my indoor garden, I have an outdoor vegetable garden. I  just recently moved these plants inside my screen-enclosed pool area. Question: Do tomatoes , peppers,etc rely on bees and other insects to pollinate and create the fruit ? So if these vegetables are enclosed..... they will not ever produce fruit because insects and bees cannot get to them..... is this correct ?
thanks in advance

Thanks for your E-mail. I am always happy to help, if I can. You have a good question, the answer is it depends if the plants are self pollinators or cross pollinators. Cross pollinators are plants that produce flowers that are usually big and showy (iris, rose, orchid) commonly the male and female flower parts are contained within the same flower  (Link to plant sex parts) but for genetic of physical regions the plant cannot fertilize itself. These plants usually need an insect pollinator or if you are breeding YOU to help them get fertilized. (link to animal vs. plant pollinators)  self pollinators do not need an insect or other mechanism to create fruit. Wind pollinated plants put their pollen into the air and it should pass through a screened in area. These plants usually have small flowers, like grass, if you notice your yard gets ‘funny’ things on the tips in the spring or fall, these little ‘things’ are the flowers.

Insect-pollinated vegetables that won't produce fruit well in an enclosed area without your help or insects are: cucumbers, eggplant, gourds, muskmelons, mustard, okra, parsnip, most peppers, pumpkin, rutabaga, squashes, turnips, and watermelon You may want to collect some pollen from some of your pepper plants all the flowers should produce it, and use your finger or a brush etc. and put the pollen from one flower (or better yet from one plant) into another. Look at my past blog posting about how to transfer pollen.

Wind-pollinated vegetables include: beets, chard, all types of corn, and spinach.

Some self-pollinated vegetables safe to grow screened in are: bush and pole beans, lima beans, chicory, endive, lettuce, most peas, and tomatoes. These plants don't need any help they will produce fruit if they get enough light and nutrients.

Good growing,
Dr. E.R. Myers


E-Mail -- Fertilzer and Flowering

Hello Dr. Myers,
    My plants are now ready to be switched to the flowering stage. With so many products on the market, I don't know which flowering formula to use. According to the grow guidelines on htgsupply.com’s website I should use a 10-30-10 ratio? I am growing in soil and using a 400w HPS.

Could you please inform me as to which products (by name) I should use now. Thankx for all your help.

Growing in good soil means the fertilizer you use is less important since soil has nutrients in it your plants can use.  I know some growers that only use soil and compost and have excellent results. I have not used all the products from HTGSuppy.com so I don't like to recommend specifics.  However, I personally use a lot of Fox Farm products, and Hammer Head when my plants are flowering and have no complaints. The ratio from HTGSupply.com is correct, basically, you want to have more phosphorus (middle number) than nitrogen (first number) Some people say to give plants NO nitrogen when flowering but I disagree, plants need nitrogen through all stages of life.  You will be fine as long as you give them small amounts of nitrogen and never more as a percentage than P or K.  The reason you should not use too much nitrogen during flowering is it tends to promote vegetative growth and in excess will inhibit flowering while phosphorus promotes fruit/flowers. The last number (K) potassium is good for all around plant health and should be given at all stages of plant growth. Sorry I can’t be more specific, but it would be best for you to find what works best for your grow area and your plants. I know Fox Farm products have a good reputation and I have used them for years but there may be other brands that work better for you. If you can, get two fertilizers and use each on 1/2 your plants and see if it makes a difference.

I have shown that too much fertilizer is bad for plants(at bottom of LINK) so do not over do any fertilizer!
Good Growing,
Dr.E.R. Myers