Why are these Plants Dying?

by Dan
(New Zealand)

My friend is running a four pot hydro system which started out great, but now it's in the flowering cycle (probably around two weeks on this stage). Three of the four are wilting and look like they are dying. I was wondering what would cause this? The pH and CF readings were too high, so we changed the water and got everything right, but it has made no change.

Answer: Dan- There are a number of things that could have caused your dying plant syndrome. The wrong pH could have done it, but the more likely suspect would be the "too high" CF reading. From what I have read, I would have to guess that your plants have been over fertilized. Having the nutrient solution strength too high causes damage to the roots, which prevents the plants from taking up nutrients properly, which causes damage to the rest of the plant above ground. The damage to your plants depends on how severe the problem became....from relatively harmless leaf-tip burn to having nearly every leaf on the plant turn brown and crispy in as little as one or two days.

The good news is, this is a mistake you are likely to avoid in the future now that you have experienced it. The bad news is, once the damage has been done, there is no quick fix....your plants will take several weeks to recover (unless the damage was too severe) and your yield will be much, much smaller than it should have been.

Your problem is a common one....perhaps THE MOST common one. Many people get into hydroponic gardening not really understanding what they need to do for success. As long as you have provided adequate light, good temperature control, air exchange, air circulation, and you do not have any indoor garden pests (like mites), than the whole secret to hydroponics is maintaining your nutrient reservoir properly.

For starters, you should have a light proof nutrient reservoir, and whenever possible you should prevent any light from coming in contact with the nutrient solution. More importantly, your system should provide 3/4 to 1 gallon of nutrient solution per plant- any less and the changes in the nutrient solution strength and pH happen too quickly to stay ahead of. Even with 3/4 to 1 gallon of nutrient solution per plant available, you will still need to check (and adjust) the nutrient solution strength AND pH at least once a day.

Obviously, this means having an accurate TDS, EC, or CF meter and a pH test kit (or meter). Furthermore, you need to dump out the old nutrient solution and start over with fresh, room temperature water and nutrients every two weeks- otherwise the solution may have a nutrient imbalance and could be just as damaging to your plants as over-fertilizing them. It is important to use room temperature water for your water changes, as I have seen cold water straight from the tap "temperature shock" the roots and kill an entire garden almost overnight.

If you are not sure what nutrient solution strength your plants will tolerate, than you need to increase the nutrient solution strength slowly week after week and keep a sharp eye out for the first signs of leaf tip burn. At that point, you may want to back off the nutrient strength just a little bit and make a mental note of this as your "upper limit".

If your plants are wilting, but not actually turning brown and crispy, than you may simply have the plants too warm under your grow lights. A temperature probe at plant-top level, directly beneath your grow light, should not read more than 80 degrees (unless the garden is being supplemented with CO2, in which case 85 degrees may be OK). For more information on properly maintaining your nutrient solution, be sure to check out my how to grow hydro page. I hope this helps you figure out the problem Dan, and Happy Growing!