Ask Erik

Hi,

I am growing Bonsai trees indoors from October to April. I have been doing this for number of years, they are under florescent tubes. They are doing okay, but not growing as well as they should. I am thinking of switching to metal halide light. The room is 10X10'
My question, should I get one 1000 watt bulb or four 250 watt bulbs?

Thank you, Peter

Peter,

By switching to an HID lamp such as a metal halide, you can dramatically increase the intensity of the light available to your Bonsai specimens. I would imagine that you don’t want them to grow too quickly, as they may begin to loose their trained shape (which doesn’t come over night), so take note of the potential for increased growth rates. An HPS lamp will give you more lumens per watt of energy consumption, but the light emitted from a metal halide is often more akin to daylight. As a result, metal halide bulbs can provide closer internodal distances in some plant varieties. Metal halide lamps with 7000K ratings are often referred to as “daylight” lamps because their spectrum looks very natural to the human eye, and the increased levels of light in blue-end of the light spectrum can contribute to more compact growth patterns.

If purchasing 4-250W lighting kits the initial investment will be considerably higher than a single 1000W kit. However, you have a lot more flexibility in terms of lighting arrangements. Also, by having light originate from several points instead of one, you reduce shading and you can spread the plants out a little more as the light will overlap between lamps. Smaller wattages also run cooler so you can space them closer to the plants (possibly increasing light intensity available to the crop). They are also safer, as lower voltage levels are being discharged. If you decide to invest in multiple lighting kits in smaller wattages, consider blending metal halide and HPS lamps for optimal results.

Sincerely, Erik Biksa

Erik,

I have heard of many products such as Karbo Boost, Carbon Max , Liquid Carbon etc. that are basically sugar. Can I just use good old fashioned “fructose” as an additive and achieve the same results, or is the sugar in these products broken down or modified in some way to make it more utilized by the plants?

Thanks, Mary

Mary,

The end product of the photosynthetic response is the production of glucose (C6H12O6), which is sugar in a simple and available form. The labels on the products you mentioned claim that they contain a blend of simple and complex sugars for optimal absorption and utilization by the plant. By providing only one source of sugar (fructose) you may mimic the benefits of the store-bought products, but only testing would determine which would work as good or better in your particular growing situation. Good luck, and please feel free to share the results with our readership.

Cheers, Erik Biksa

Erik,

I have a simple aero/hydroponic system setup using a Rubbermaid container, PVC, a water pump, etc ... It is set up in a closet, with an exhaust fan and a 400W HPS lamp just like all the systems I read about, but the inside of the reservoir/grow chamber heats up to well over 90° due to heat from the HPS light. I have painted the outside white, cut ventilation holes, and installed a small fan to circulate air, but it still gets too hot. What else can I do? The rest of the house is around 70°, and the closet air outside the reservoir is around 80°. Any help is appreciated.

Thanks, from Grateful Reader

Thanks for your question, for which I too am grateful. A few solutions come to mind.

If you are running an oil-filled pump continuously, it will heat up the nutrient solution. External pumps tend to heat the solution less. As long as the chambers containing the roots drain completely and will not overheat, you can run the pump intermittently on a timer.

If possible, move the reservoir to the outside of the growing room. As long as the reservoir is lower than the drain, the water will flow back from the system, even if it has to go through a pipe installed through a wall. Use a larger diameter pipe than you would normally use, to facilitate rapid drainage. You can also run the delivery line(s) through walls, etc (be mindful of condensation). However, you may need to increase your pumping capacity to achieve the same pressure as before.

If you are unable to relocate the reservoir, you can reduce the amount of heat radiated from your HID lighting. Start by keeping the ballasts outside of the growing area. Enclosing the lamps in an air-cooled reflector will keep things cooler by reducing the amount of heat introduced from the lamps. A common misconception is that light will be lost through the glass. Although true in one respect, it does not account for the closer lamp to canopy tolerances that only air cooled or water cooled lighting allow. This more than makes up from the wavelengths lost to the protective glass.

I am not sure of the size of your growing area or your exhaust fan CFM output, ducting, etc. However, by increasing your exhaust output by using larger diameter ducting and high-output centrifugal or shaded pole blowers you can quickly evacuate the heat before it has a chance to heat up your reservoir. The increase in air movement almost always results in a positive increase in terms of crop performance.

You can also add stainless steel or titanium cooling coils or use a water chiller that will not react with your nutrient solution. However given the scale, these probably are too great of an investment. You can also insulate your reservoir.

First, place your reservoir in a heavy gauge garbage bag. Enclose with tape (of course leaving the top open; kind of like a garbage can with a bag on the outside). Now, pop this into another garbage bag. Fill the space between the two bags with insulation and seal the rim at the top with durable tape. Although puffy, your reservoir should stay considerably cooler. Make sure that all of the insulation is well sealed within the layers of plastic. You don’t want this stuff coming loose and finding it’s way into your crop. You can also throw a block of ice into the reservoir at the beginning of the light cycle if you have the time or inclination.

Sincerely, Erik Biksa

Erik,

Last year I purchased a set of hydro nutes made by the local hydroponic shop. After a couple months I noticed there was a strange, wispy precipitate in the bloom formula (kind of looks like pieces of torn up plastic grocery bags floating around). At first they were only here and there, now there are a couple for every few ml’s I pour out. I always shake the bottle quite vigorously before pouring anything out, but they just keep on coming. Could this precipitate be damaging to the plant?
Thanks, JJ

JJ,

If the product inconsistency you describe originated from a popular manufacturer’s bloom formulation occurring in the early part of 2002, your biggest concern would be clogged emitters, lines, pumps, etc. Your second concern would be to return to the place of purchase and exchange it for a fresh bottle. Of all the feedback I have received it did not harm plant growth, but was a nuisance in terms of clogs, etc. Apparently the substance found in the bloom solution contained no DNA when tested at a nationally recognized independent laboratory and is therefore very unlikely to pose a problem.

Sincerely, Erik Biksa

Erik,

I’m using clay aggregate as a media. I was just wandering how you sanitize it for reuse? I heard something about using the oven, but at what temperature and how long do you leave it in?
Thanks

Thanks for your question,

The oven is a great idea for smaller scale growers to sterilize their growing media (pasteurization). You might create a bit of a stink though, which could be a concern if you are an apartment dweller or sensitive to odours, etc. I think that relatively lower temperatures for longer periods would be more effective for eliminating pathogens, etc., than applying higher levels of heat for shorter periods of time. An oven proof thermometer inserted through to the centre of the mass will assure you that ALL the growing medium is sterilized. The centre of the mass may take longer to reach the critical temperature, as it is somewhat insulated versus the surrounding material.

Most pathogens are eliminated when exposed to temperatures near 150°F for prolonged periods. I would recommend setting the oven to 175°F and adjusting the temperature accordingly to maintain the temperature within the center of the mass of growing near 150°F for a period of 24 hours. However, you may still have bits of roots and other decaying organic matter left in the growing media. You should try to remove as much of this as possible before setting into the oven. Afterwards, when the growing media is moistened again, the decaying organic matter that remains may become a food source for microbes.

If you have a healthy population of “good” microbes, this shouldn’t pose a problem. However if anaerobic conditions were to occur, you may have a population explosion of “bad” microbes which can lead to problems including root disease. Using products containing microbial inhibitors will control the microbial load, while some enzymatic products will accelerate the break down of organic matter in the media.

Smiles, Erik Biksa

Erik,

Hello. I am looking for a natural control for spider mites that will not harm caterpillars. Is there such a thing?

Thank you, Shari

Shari,

The first choice would be predatory insects such as Phytoseiulus persimilis which prefer to consume spidermites. Luckily, they also do a pretty good job of it as long as the spidermites are detected before their population numbers become significantly high. Also, given the sheer size of a caterpillar versus a predatory mite, I would put my money on the caterpillar any day. Predatory mites can be found at your local hydroponic shop. You might give the shop 24 to 48 hours notice, as they usually have to be ordered in on a per demand basis. They are usually sold in lots of one thousand and are relatively inexpensive when compared to chemical pesticides. If there is no local shop around you, visit the internet and look for suppliers in your area. With overnight mailing, distance is often not a problem.

Cheers, Erik Biksa

Erik,

I grow in a one gallon pot full of hydroton and one-three inch cube. The pots are placed on a homemade table, with spaghetti line to each pot. I use GH nutrients, Nutriboost{stress}, Potaciumsilicate by Grotek, Monsterbloom and H2O2 about three times a cycle in small doses.

The water runs while the lights are on and twice for 30 minutes while the lights are off.

The plants were placed on the tables and were fine. I left for five days and had a friend to watch them. When i arrived home, the plants were starting to wilt, the stems of the leaves were reddish purple and the stalk started to streak the same reddish purple. My room is 82°F with the lights on and 70°F with the lights off. Humidity is 55 to 62 % when lights are off and 45 to 50% when the lights are on. The first thing I did was check my pH probe. It was dirty, so I cleaned it. When I calibrated the meter{nutridip} it was out by .3, so I assume the pH was actually 6.6 or 6.7. Secondly, I flushed my plants with temped water and sprayed half strength growth plus. The next day, the plants had perked right up. They looked great. Two days later, they started to show signs of phosphorus deficiencies and a slight wilt again. Two days after that, they started to pale while keeping the reddish purple in the leaf stems and the stalk. I waited two more days until weekly flush day. I flushed with temped water and gave the plants a light mist of water. Then, an hour later, gave them half strength Green and Stay Spray. They did not perk up. The next day I went to a store and told them what I had done and they said my Magdrive pump could be causing the problem. They said I was probably lacking in calcium, magnesium and iron, so he gave me calcium to add.

Will Magdrive pumps cause calcium, magnesium and iron to become deficient?

The last two cycles were not very good. We had gotten new plants from a different place both times. We think that we might have brought in a virus but we try to keep everything as clean as possible. The symptons were sort of the same as the times before.

We use H2O2 to clean all lines (at 10ml/gal). We also use the same mixture to clean the rooms with.

Before we changed, our plants we were doing fine. Are we not clean enough? Is there a virus? Is it the pump?

We had a bug that we called a root aphid. I have looked and can find almost no useful information to kill them.. Could you help us? We would like to use something somewhat friendly to all of us.

Would a water UV light be fine to use on the nutrient solution help?

Thank you, Vancouverite

Thanks for taking the time to provide all of the detail,

It helps to take out some of the guesswork although the problem does remain a little perplexing. The “friend while away” syndrome has impacted more than one grower, but is not necessarily the source of your problem.

The first area of suspicion would be the homemade tables and irrigation system. Examine the materials you used for construction very closely. Is there any metal (other than stainless steel) coming into contact with the solution? Did you use any adhesives other than natural silicone? Is any sort of chemically treated wood coming into contact with the solution? The problem sounds like something phytotoxic (poisonous to plant growth) is finding it’s way into the solution. It’s possible that your make-up water contains toxicities (older plumbing?). Have a drinking water analysis performed on your water if in doubt. Also, off-gases from fossil fuel burning heaters can be toxic to crops (i.e. ethylene). If you have a natural gas or propane fired heater, make sure that it burns with a pure blue flame and is running efficiently (same with CO2 generators).

Secondly, how you go about applying H2O2 can have an affect on the nutrient solution. If H2O2 is added to a nutrient solution, it has the potential to oxidize nutrient compounds, rendering them unavailable to plants. Iron, zinc, and copper for example, require chelating or complexing agents to remain available for plant absorption. The H2O2 is capable of dissipating or breaking apart the chelating or complexing agent(s).

The magnet in the Mag-Drive could attract the iron oxide and other metals which result from the degradation of chelated nutrients in the solution. The electrical charge of most nutrients in chelated form should be neutral. H2O2 should be used for pre-treating the make-up water a couple of hours before mixing in nutrients.

If the plants have come from different sources at different times (essentially different plants), it’s not as likely that the problem is viral. Viruses are usually transferred through successive generations of clones (once the plant material has a virus, it usually remains in the tissue sometimes with the exception of the first ¼” or so of a rapidly growing shoot tip). If the root aphids are a re-occurring problem, they could be infecting fresh, untainted plants with pathogens if they are piercing the roots in their feeding habits. Nematodes are a biological control of some root pests. Alternatively, neem drenches may offer a level of control. Try treating the room with an anti-microbial solution instead of the H2O2, its worth a shot in case the problem is a result of previous crops. Although, it sounds as though you are pretty adamant and the growing environment you describe is near optimum. Consider replacing your irrigation system, as all it takes is a couple of bad microbes. Applying an anti-microbial solution in the system every seven to 10 days can help to prevent future outbreaks. I hope that you find your answer in this response, otherwise drop us another line if you like.

Cheers, Erik Biksa