3 Reasons Why Your Plants Are Dying: Common Killers of Indoor Hydroponic Gardens

The only thing more frustrating than a dying plant is having no idea why your plant is days away from biting the dust. Since gardening can be a patience demanding practice, it's no surprise many shed tears when they lose a beloved plant 3 months into its 4 month life span. In this short guide, I'll run through the most common killers for the beginner or intermediate hydroponic farmer so that you can learn from the mistakes of all the heartbroken growers who had to learn the hard way. 

Before I begin detailing what can go wrong, let me preface this post by restating a few tenets of Integrated Pest Management (IPM) as they apply to your indoor garden. First and foremost, a bad growing environment fosters a weak plant and a weak plant is the preferred target of any pest or disease. Nutrient deficiency is never as fast and brutal to plants as pests or disease so keeping your plant happy is the surest way to avoid a quick disaster. The quick rundown is as follows:

Keep your plants in an area where it's comfortable for them; not all plants tolerate the same conditions so do your research. Brassicas and leafy greens generally like it cooler (55-75 F) while fruiting/flowering plants like it a tad warmer (70-85).  Humidity is also an important factor as fungi and bacteria love cool, moist conditions so try to keep your humidity low, especially in cooler climates. A great method of controlling humidity is to have good air circulations using fans or passive vents. Hot air leaves from the top, pulling cooler air from the bottom, remember this when you're configuring any vents and keep in mind that if any bugs are around your area this is also where they can enter! The next step is simply to monitor your grow area as thoroughly and often as you reasonably can. Once a day is optimal, but you can get away with less once you become more familiar with the environment. Keep a log of your nutrient addition schedule, take pictures, and inspect the plant closely for signs of even the smallest bug, fungal spore or bacterial spot. Take it easy, no need to whip out a magnifying glass, but these efforts are your first line of defense. Now on to the carnage....

1) ROOT ROT:
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If there ever was a wanted poster for the silent killer in hydroponics, Root Rot's fungal mugshot would be plastered front and center. Your plant can go from healthy to drooping in a matter of days, leaving you perplexed as there are no signs of disease or pests on the leaves or stem. Only once you pull your plant out you'll see the blackened, slimy aftermath of a root system ravaged by this fungus.  ​

The brown and slimy telltale signs of Root Rot.

tIn this case the best offense is a good defense: Root rot loves a hydroponic solution lacking in oxygen and beneficial microbes. Sizing your container properly so that your roots don't mat together and form dense knots will also prove effective in keeping your roots inhospitable to Root Rot. Beneficial microbes also serve as defensive competition for the surface area on your roots and help digest and break down any dead material before root rot can sink it's teeth into a buffet of decaying roots. Adding oxygen through the use of air stones and an adequately sized air pump is an absolute must to keep your plants healthy growing optimally. Last but not least, adding about 3 mL of 30% hydrogen peroxide for every liter of nutrient solution [3 mL/L] can halt or deter root rot from setting in and is my preferred line of defense prior to using the expensive big guns like Cannazyme or other digestive enzymes to break down decayed roots. 

2) POWDERY MILDEW / DOWNY MILDEW / GRAY MOLD

I'm clumping these three fungal delinquents in one group because they all have several key signs and prevention methods in common. While each type of mold may be specific to different varieties of crops, there's always one ready to invade your lush plants at the first sign of weakness. These three (and similar perpetrators) are lovers of the extremes: too dry, too cold, too wet, and too hot. 

Powdery Mildew on A Cannabis Leaf

Downy Mildew on A Grape Leaf

Grey Mold on a Tomato Leaf

This terrible trio loves the damp micro-climates of stale, un-circulated air under leaves, around bushy stems, and in your precious flowers and fruit. Anything that's wet, decaying, damp combined with a climate that's too cold or hot is a breeding bed for one of these fungal plant diseases. Distinguishing between the three is not as important as knowing your defenses. Keep your plant well trimmed; any leaf that is not actively healthy and not contributing to photosynthesis (i.e. shaded by other leaves) can generally be trimmed and discarded to increase air flow in your plant. Circulate the air with oscillating fans to keep the environment free of damp, stale air. Any signs of this disease or decay should be dealt with by carefully removing the infected leaves as you don't want to spread spores, and discarded in the trash. DO NOT COMPOST DISEASED LEAVES! Other preventative measures such as foliar compost sprays and/or biopesticides such as B. Subtilis (Serenade) are great options to stop these molds from colonizing your crops. One final note is to harvest your fruit as soon as it is ripe; mold will blossom on old and rotting fruit. 

3) THRIPS / MITES / APHIDS / WHITE FLIES

OH MY! Again, I've clumped these pests into a group of the most common culprits for giving gardeners a headache. These critters may be very hard to spot for the beginner grower before it's too late. Keep an eye out for the favorite congregation points: Fresh new growth, undersides of leaves, and in the nooks of branches coming off the stem. Other obvious signs of spider mites are tiny black dots that leave web-like material (hence spider) leaves and stems. If you're growing indoors you will be much less prone to these pests, but do not be complacent and continue to do close examinations of your plants. Be wary of introducing store bought plants to your environment without thoroughly checking for signs of these pests as many nurseries and grocery stores offer infested plants unknowingly to customers. Look out for the signs of pest damage by looking for abnormal leaf curling, puckering, discolored white spots, or yellowing/dying leaves. Anything short of a healthy plant is a reason for suspicion so keep your eyes peeled for the tiny critters.

Spider Mites Hanging Out on their Webs

Thrips hiding in the nooks of adjacent stems

Aphids love the leaf undersides, and feeding on succulent new growth

White Flies congregating under a Leaf

While these pests are only deadly to your plants at levels of heavy infestation, their initial appearance should be recognized as a red warning sign to an imminent uphill battle should you not take it seriously. Action at the first signs of pests is your best option, aside from the preventative environmental management. Squishing aphids by hand, or trapping white flies in sticky traps is a great way to curb the growth curve so that things don't get out of control too fast. Using beneficial insects like lady bugs, predatory mites, and lacewings are excellent pesticide-free and organic methods of controlling pest invasions.  Other options like Azamax and Neem Oil are good too, however many find the pungent smell of neem oil to be off-putting so many opt for insecticidal soaps derived from fatty acids to be their preferred method of pest control should they need a spray. Regardless of the method that works for you, the solution to an already infested plant can be messy, time intensive, and frustrating so your best bet is to keep your area away from pest entry points, and your plants as healthy and vigorous as possible as pests love a weak plant.

In short, these diseases can be a terrible fate for any gardener and their plant. If you run into any of these or other problems do not dismay as there is no such thing as failure in gardening, only lessons in ways to do it better next time. Keep your plant healthy, your environment clean and favorable, and monitor your plant as frequently as you reasonably can. If you keep good records and stay observant you'll have a much better learning experience should your grow be a success or a painful lesson. Remember to do your research on the temperatures and conditions that your particular plant prefers, and practice getting a good start as early as germination. Above all, never stop having fun. Enjoy the process of learning and growing as a horticulturist and you'll gain much more than just a harvest.


​Cheers and Good Growing!