E-mail -- The Right Light and Yellow Leaves

I have a question. I have a 6' X 3' space for my indoor flowering. I have a HTG 150 HPS light and a 400 HPS light.
I only use the 150 as it seemed the 400 was too strong.   Question: is a 150 HPS bulb suitable for this space? or should I buy another150 HPS lamp. What is the perfect lighting situation for this space?
As always Thanks in advance.
What do you mean too strong? too bright or too hot? Either one could be helped by raising the light away from the plants. Unless you are growing in a crawl space you just need to lift up the light. I'd not spend your cash on another 150 when I think a 400 W is needed for your space. Let me know what you think was the problem with the 400W hps because that is the light I'd recommend for your space.

Good Growing,
Dr. E.R. Myers
Well my situation is this..... I don’t have a green thumb !! I always seem to water or add nutrients at the wrong time.  I try to add water every other day and I stick my finger in the soil about 2 inches to determine when to water. I add Miracle Grow (15-30-15) for vegetative stage and 10-54-10.   I have some flowering plants that have turned pale yellow (leaves) and they are withering and falling off. I thought it was either low N or the 400 HPS was too strong (it is 3 feet from the top of the plants). So I switched to 150 HPS.

I can’t decide correctly what exactly the issue is. The plants are not talking to me. I have another batch ready for flowering in 3 weeks so I am going to take your advice and use the 400 HPS instead of the 150 HPS and raise the lamp. It’s just that sometimes I worry about the heat coming off the transformer from the 400 HPS even though I have a dedicated fan just for this heat source. I’m learning Thanks again.
Hello again,
Ok, it sounds like you are watering your plants too much... that also causes leaf yellowing. Let the soil on top dry out completely and pick up or tip the pots to see if they are heavy with water.  Also, get a thermometer with min. max if your temperature by the plants does not go above 90F you are fine with the temperature.
Good Growing,
Dr. E. R. Myers
Yes Sir!
You are right on target. Overwatering. All of my 3 gallon pots are heavy with water. I need to not be so "hands on". They will be completely dry on top before I water again.
Thanks Dr. I appreciate your help!


E-mail -- A need for cooling the closet?

Hi Doc,

I am looking to purchase a 400 hps light set from HTGSupply.com and I was wondering if it would require cooling if it is left in a 12-12 cycle. I am limited in terms of cooling as I do not want to destroy my closet and am not able to drill anything. How could one go about cooling this machine for under $50 effectively?

 The 400 HPS is a good all purpose light. The answer to your question depends on the size of your closet. I also have a 400 HPS in a closet that is 4X10X7.   I have a carbon filter and duct blowing over the plants at the bulb to move the heat around and my temperature never gets above 85F if I leave the door shut 24/7. That may seem high but it is ok for most plants. It would be a good idea to get a thermometer from HTGsupply.com that has a minimum and maximum reading and put it in the closet. If the temperature never goes above 90F you are fine. If it is over 100F, and you are not growing cacti, your plants won't grow to their full potential. (This means you need to do something).
Keep in mind the temperature by the plants is what you need, if it is 100F+ at the top of the closet but two feet under the bulb it is 85F by the plants you are fine.
If your closet is a small closet and your temperature by the plant tops is over 100F you have to do something. The easiest thing is to have the door open during the 12 hours ‘on’ cycle. If you can only open the door for a short time the best time for this would be near the end of the light 'on' cycle when the temperature will be highest. The problem is you may forget to shut it and irregular dark and light cycles will lead to plant stress which will lead to poor plant growth and flowering.  Keep in mind, it would be better to have a few ‘hot’ days then changes in day length.

The next thing to do is to use a fan to move the heat away from the plants. The fan and door open will work better together. You can also try raising the light higher above the plants to see if this cuts down on the heat right by the plant tops.

If you have a small closet and think the temperature will be 100F or more and having the door open is not an option, you may want to use T5-HO fluorescent lights. You can get flowering bulbs that are high in RED light if you are interested in flowers. I say this because I had a small closet (3x3x7 feet) once and even a 250 Watt HPS needed to have the door open or it would get close to 100F by the end of the lights on cycle.

I should also mention finally that I think a 150 watt LED or two might also be an option if you are worried about heat.

Good Growing,
Dr. E.R.Myers

Yous could also send an E-mail to Sales@htgsupply.com, the sales manager Perry knows how to use all sorts of equipment and might have something in your price range.


E-mail -- Are You Ready for Hydroponics

I want to grow indoors this winter and have a 4 x 4 x 6 grow tent. I want to try hydroponics but I'm so confused about the different systems. I need an easy to maintain system because I'm only growing a few plants. Do I need all the equipment for pH and specific gravity etc? It doesn't seem worth it for four plants. Is there a simple, robust system you can recommend? I already have a 400 hps light too. Thanks!

It sounds like you are not ready for hydroponics. You must check and maintain the pH etc. A friend once described hydroponics to me like this, “Hydroponics is like a race car, it can go fast but it needs a lot of work done on it or you will crash”.

Since you are looking for easy growing, I suggest you use 5 gallon buckets with a soil mixture. Soil does not need to be measured and adjusted with a pH meter. All you need is some fertilizer and water to go with your 400 HPS . You can add different mediums to your soil depending on how you water and what plants you are growing.

If you want to get two crops in over the winter you can reuse the soil. After you use it two times, you can put it in your outdoor garden, compost or a flower bed.

If you are looking for the easiest way to grow plants it is in dirt.

Let me know if you do want information on various hydroponics systems. 
Good Growing,
Dr. E.R.Myers


E-mail -- Optimal Plant Height and Spacing

Just wanted to know how tall a plant can a 400 watt HPS light grow well ?

To be funny I’d say as high as you can raise the light. The problem is you will only have growth on the top part of the plant if you grow them too tall. From my personal experience I have grown many plants 3 feet high under a 400 W HPS

However, It depends on how close you have the plants to each other and the plants growth habit (branching or single stem).  Also, the container size and how you space the plants will determine how tall they can grow. (Plant spacing LINK)
Basically, if you space your plants further apart, the light will penetrate further and you can grow plants that are taller (but fewer of them) and the opposite is true, if you crowd your plants close together, the lower leaves won’t get enough light and will start to drop off meaning you won't get any flowers/fruit on the lower part of the plants but you will get more plant tops.
In a nutshell, I would not have your plants get much taller than 3 feet with a 400 W unless you are growing corn or some other slender tall plant. If you are growing a plant that has branches, you want leaves all the way to the bottom of the plant. You could put some side lighting like a florescent mounted on the wall a foot above the pots and then you could grow taller plants.
One thing you should do is notice if there is just a bare stem on the bottom of the plants as they flower, if so, next time start to flower the plants when they are a bit shorter.
Having a bare stem is not bad, but space is usually limited indoors and unless you are growing plants for stems, there is no reasons to have the plants make extra stem and less leaves/flowers.
I hope this helps.

Good Growing,

Dr. E.R. Myers


E-mail - Good light for starting seeds

Hi Doc. I love your website. Very cool.
To start seeds I bought a 4 bulb fluorescent fixture and installed 2 full  spectrum bulbs and 2 aquarium bulbs. Is this good for starting seeds so they don't get leggy or should I just go with the regular shop lights?

Also, I have a ballast labeled for a 440 watt HPS. Does that mean I can not use it with a 400 watt MH?
Any other advice?
Thanks very much.

Hello, Thanks for the kind words about the website, I hope this site helps people grow well.

Any florescent is good for seedlings. Your bulbs are good. You could get similar results with cheaper cool white bulbs from a hardware store. In a couple years when you need new bulbs go with them...Make sure you keep the bulbs no more than one inch above the tops of the plants. If you have the fluro's more than an inch or two above the plants they will get lanky.  If people use the HO T-5 from HTGSupply.com you will keep the light a few inches above the plants.

The 440 watt HPS uses 400 Watt HPS bulbs. the extra 40 watts are for the ballast. You can NOT exchange an MH and HPS bulb they are very different!!! Unless you have a new digital conversion ballast. Contact Perry at Sales@htgsupply.com with specific questions about your light if you got it at HTGSupply.com

You should get a new HPS bulb every 2-3 years to maximize growth and flowering. A root warmer would help speed up germination.

I have also used the Tri-Band from HTGSupply.com to grow seedlings successfully. (See seedlings growing under LED)

Good Growing,
Dr. E. R. Myers


SET UP III Plant size, spacing and pruning

There are many types of plants you can grow indoors so there are many genetic differences in growth rate and potential size. No matter what plant you grow, you can affect growth. If you keep the plants in small containers  you will make plants smaller. You can induce your plant to flower earlier making the plant smaller. If you want larger plants you keep them in larger containers and let them grow large before inducing flowering. Plant size is controlled by specific genes so it is something that is easy to include in a breeding  program, if you are interested.

There are many different opinions on how much space a plant needs. Basically, the closer you space your plants the less room they have to grow. So, you have two choices grow many small plants close together or several large plants spread out. You need to decide what type of plant spacing will work best with the light and area you have. In general, the total growth in a room with many smaller plants will be greater than a few larger plants. This may not be true with all plants, some may not be able to grow in small spaces and flower/fruit successfully.

The final height of the plant also determines the space needed. A 10 foot plant will need at least 4 feet diameter of space to grow; a 4 foot plant will need 1 foot diameter etc. You can prune or train plants to be smaller and fit into your grow area if their growth habit does not exactly fit your grow space.

With pruning again there are two basic ideas -- prune the plants and don’t. I don’t like to prune, removing leaves is bad as the leaf is an organ of a plant that makes sugars to provide the plant energy.  I think what I don’t like is that people think pruning will make a plant grow better. It won’t. It will make a plant grow the way you want it to, with a specific shape or size, which may be better for you but is not for the plant. If you don’t prune your plants indoors you should have an HID like me that emits light that can penetrate several feet. If you do not have an HID, you may find it better to prune plants so that the plant grows directly under the light. Another option I like is to tie your plants down instead of pruning. This leaves the leaves on the plant to gather light and keeps the plant in the area you have to grow it in.

Good Growing,
Dr. E. R. Myers


SET UP II reflection and air flow

Once you have the space chosen you need to do and think about a few things before you put the plants in there.
1st Clean --  I know this is not going to be the most fun part of growing but it is important and can help reduce countless problems later. This is going to be the home of your plants so clean out all dust, debris, and wipe down every surface (walls ceiling and floor) with warm soapy water. If you have had pests or disease use 5-10% bleach or hydrogen peroxide or isopropanol. Plants give off moisture so if you think you can continue to use your closet as both a closet and a grow area you better think about how humidity will affect the things other than plants you keep in the closet. (See ventilation below)
Reflective surfaces – The amount of light that hits the plants will increase growth and you can greatly increase the light getting to the plants by having reflective surfaces. This is extremely important with HID compared with the more linear light put out by LED”s and fluorescent lights. Some good reflective materials are mylar,  flat white paint, aluminum foil, cardboard or plywood painted white, or even white cloth. You should try to cover all areas so that all the light gets reflected around until it is absorbed by the plants. Everyone thinks to cover the walls, but the floors and the ceiling should be made as reflective as possible too. Light can travel 186,000 miles per second so it can bounce around on many things in your closet. If you think you don’t have any reflective material I bet you have aluminum foil in your house right now (Even if you don’t have it you can get it with a few coins at the grocery store so go get some and notice the difference). Good growers use wide heavy duty aluminum foil in areas that won’t be disturbed and use cloth or plastic curtains where you will have to move the reflective material to get to the plants. It is easier to hang foil vertically (up and down) than horizontally (left to right).
Ventilation Most people think to ventilate to remove humidity and heat but most importantly you should do it to provide your plants a fresh source of CO2. I have grown plants in a closet without true ventilation. I would open the door each day to refresh the air and I had a small fan in the closet (It was 3x4 roughly). That is all it takes is light air movement and occasional refreshing of air to grow plants bigger and better.

One thing I like to use for ventilation is a carbon filter. You can run one in your grow room and direct the airflow over your plants at the bulb to increase airflow and reduce heat around the plants. The added benefit is the carbon filter cleans the air of many fungal spores and other diseases.

Good Growing,
Dr. E. R. Myers