Ask the Professor – Prev. Questions 2

Professor –

Ok, I found another hydroponics site that talks about feeding the seeds a solution, but they measure the solution in parts per million, how do I measure out to parts per million” This is delaying me from starting my hydroponic greenhouse. I talked to a lady here, and the hydro plant food she sells says to use one(1) table spoon for grown plants and 1/4 to 1/8 for new starting seeds (this is per gallon of water). Help! Information overload! The site I saw was saying to use less than 500 parts per million for starting seeds.

Jim C.

Jim –

A very mild nutrient mix will not hurt your seeds, but in my experience, it will not help either. I personally have NEVER given seeds nutrients. It is a waste of nutrients and money. I don’t add any nutrient to the water until the plants form their first “true” leaves. Then I give them a 1/4 strength nutrient solution until they start to grow vigorously. I then put them on full strength nutrient.

As far as figuring the parts per million the only way I’ve ever checked it is with an electronic PPM tester. This really isn’t necessary for the hobby gardener, but if you are concerned. The more inexpensive PPM/TDS pens start about $70 (U.S.).


Dear Professor,

I am very new to gardening using hydroponics. I have started a Horticulture Therapy Program at a local hospital and am working with sick children. I would like to include the children that have cancer but was told there is to much bacteria in the soil for them to handle. Hydroponic gardening was brought to my attention as a way that they might garden while in the hospital. What types of growing mediums would work best in this situation? Are there small projects that the children could work with while in the hospital and then take home that involve hydroponic gardening? Could you please also refer me to literature on hydroponic gardening that would be helpful in my situation? Thank you for your help.

Debbie P.


I haven’t heard about Horticulture Therapy before- what a neat idea! There are several ways that you can go about using hydroponics in the hospital. The simplest method to replace the dirt would be to use a growing medium such as coconut fiber or a good soiless mix (like Fafford’s or Promix), or you could probably go with the old reliable perlite / vermiculite mixture (50/50). Growing the plants in small pots will enable the children to easily transport their plants home. You could also do a simple water-culture system like the one we have described in our “free system plans” section of Hydro-U. The only problem with this type of system is that it would be difficult (if not impossible) for the child to take the plant(s) home. Kids really seem to like these systems because the root systems of the plants are clearly visible.



What is the best conditions to grow a mother plant and how soon can it be cloned? Also do you have to have a different grow room for the mothers?


S. M.

The best conditions to grow a mother plant will vary by the species, however, generally you would give the mother 18 hours of light and a good grow formula fertilizer. The mother can be cloned as soon as you have a growing tip(s) that is big enough to be cut (about 3″ or 4″ long in most cases). It is usually best to keep the mother(s) in a different location as the cuttings due to the size difference and different lighting requirements.


Dear Professor-

Could you possibly recommend a good hydroponic fertilizer, I have had difficulty locating them, it seems very few salespeople I’ve run across have much useful knowledge in this area. I’ve found a product called Hydrofarm, that comes in two varieties: vegetative and flowering, but the salesperson said it was for dirt farming, but could used in hydroponics, does this sound right, is that usual? Anyway, any input you can give will be greatly appreciated.



There are many good hydroponic fertilizers on the market ranging from the top of the line liquid fertilizers to the less expensive powdered nutrients. As far as I know all of Hydrofarm’s fertilizers are hydroponic. There is an easy way to determine if a fertilizer is a hydroponic fertilizer or not, look to see if the fertilizer contains “micro-nutrients”, if it doesn’t list micro-nutrients on the label than it probably isn’t intended for hydroponic use. (see more information about Micro-nutrients) If you have a hydroponic supply store in your area, they should have a large selection of hydroponic fertilizers and can help you decided which one would best suit your needs. If you don’t have a supplier in your area, you can easily mail order your product. We here at Simply Hydroponics send mail orders all over the world.



40 yrs. ago my cousin uprooted a swam magnolia & put it in his mother’s yard. It is now magnificent. He passed away 4 yrs. age he died.In his memory we would all like to taking cuttings from this tree root them and plant them in our own back yards as a living memory to him. Can you give us any help to successfully do this. We would all greatly appreciate this. We all loved him very much and these trees will be known as “Our Michael Tree”. Please help me if you can.



What a nice memorial.

Taking cuttings from magnolias is pretty straight forward. The best time to take magnolia cuttings is July and August. The cutting should be between 4 1/2″ and 8″. You will need to use a good rooting hormone. If you get a hormone that must be mixed, mix it for “Hard Wood” cuttings. For step by step instructions go to .If you follow the steps in this article you should get a 90% to 100% success rate.



The website is really starting to take shape! Good work!

  1. What varieties of lettuce are best for growing in the hot Florida summer?
  2. I am considering relocating my NFT/DFT lettuce system into a more shady location. Will the lessened light exposure be more detrimental than the heat exposure of full sun?



There are a few varieties that do pretty good in the Florida summer sun, Ruby. Oakleaf and Red Oakleaf all do OK. They will still “bolt” quickly and try to go to seed much sooner than they would in cooler weather, however, if you harvest them when they are smaller you can get satisfactory results. I have been growing lettuce all summer and I simply start seeds more often so that I have a steady supply. Moving your system into a more shady location will probably not help, it is the ambient air temperature that makes them “bolt” not necessarily the sunlight. The reduced sunlight might force the plants to become “leggy” (grow tall and skinny).


Hey there Professor,

Are there any specific advantages or disadvantages between NFT and Aggregate systems? What about versatility? Do specific plants grow better in one or the other? Would it be advantageous to create a system that included both?



One advantage of NFT over aggregate is that the NFT uses very little if any growing medium (besides air and water). Which saves time and/or money. And If you’ve ever scrubbed and sterilized a pile of gravel or grow rocks you know how much fun that can be! Replacing the aggregate every crop can be costly.

The aggregate does however retain some moisture (some more than others) which will make an aggregate system a bit more tolerant of electrical outages, pump failures, etc…However the above mentioned problems can quickly damage plants in either type system. These type systems are both susceptible to “no-water conditions” because the roots can dry out very rapidly.

The aggregate systems give the plants physical support so that less “trellising” is required. Both systems are fairly versatile. There is a vast array of plants that can be grown in ether system. I really haven’t heard of any specific plants that prefer one type of system over the other. A plant that does well in one should do well in the other.

I see no real advantage to a hybrid NFT-Aggregate system. The aggregate would just take up valuable air space in the root zone.



Could you please advise what may be the cause of my Ipomea plants showing tip burn and the new growth is very yellow. If you have any other information on growing these it would be very beneficial to me. Other known names Ung Choi or Kang Kong.



What you describe sounds like a magnesium deficiency. Try fertilizing with a mix of Azalea food and Epsom salts. These plants like a slightly acid pH (5.8-6.7) and like full sun to partial shade. These plants are annuals in colder climates and last for up to 4 years in warmer climates.



I would like to see a detailed sketch or drawing of the plumbing involved in the AquaFarm. The 2 five gallon bucket setup. Thank you for your time and effort. GIF or JPEG would be great as long as they show the details.



I have drawn up what seems to be a fair likeness of the system. Click Here to view the drawing. The heart of the system is the air-lift pump. Which operates by pumping air into the bottom of a vertical plastic tube that is open at both ends and with the bottom of the tube submersed in the nutrient solution. The air bubbles will rise up the tube which traps and lifts nutrient solution up the tube with the air. The drip ring is simply a ring of tubing with holes cut into it to disperse the nutrient solution. The ring is attached to the pumping column with a “T” fitting.