In the world of hydroponics the term “stress” can refer to a lot of things: light bleaching, overheating, overfeeding, etc… But no matter how it’s defined, “stressed” plants are those plants that you see with shriveled, drooping, and discolored leaves; brittle branches; and underneath the surface are unhealthy roots. In this article, we’ll be talking about plant stress and the various ways plants can undergo it. Whether it’s by nutrient deficiency, illness, shock, we’ll show all you fresh growers (and even some of you experienced growers) some of the most common issues facing your indoor plants all year ‘round.
Nutrient Deficiencies = Plant Stress
Nutrient deficiencies and inconsistencies will stress your plants out. Even when corrected, depending on the nutrient deficiency and how long the deficiency has occurred, the damage can (and usually will) affect your final harvest. So it’s important to catch nutrient deficiencies before they become too severe to take care of. Identifying Nutrient Stress
The good news is that nutrient deficiencies are different than light and temperature stresses, so you should be able to see that your plants have a nutrient deficiency due to discolored leaves. The leaves may bend or droop a little, but not as much as they would due to overhearing; and they won’t have white spots, weird specs all over, or holes like the ones you get with pest infestations. The problem with nutrient deficiencies, though, is that you can’t just simply look at the plant’s discoloration and say, “Oh, that’s the problem!” because a lot of nutrient deficiencies look like they could be a couple of different things. For example, Nutrient Burn (when your plants get too many nutrients and the tips of the leaves begin to fry) turns your leaves the same color of yellow and brown just like a magnesium or iron deficiency. This is why grow journals are so important! While a grower may not be 100% sure of the deficiency at first glance, there’s a lot you can learn from looking at the height and color of your plants. Certain deficiencies will allow for a harvest but the plants struggle the whole way there; others will stagnate or halt growth; other nutrient deficiencies will completely toxify and kill the plant. You’ll be able to narrow down and defeat nutrient stresses by keeping a record of the plant’s behavior and referencing its attributes with a deficiency chart.
Light & Heat Stress
When the light's too intense for your plants it will either cause heat stress or will bleach them with light. Strong grow lights will bleach and/or burn the tops of your leaves, while lights like strong LED grow lights may only bleach your leaves, so it’s important to understand what’s happening to your plants when it comes to these issues.
Now, what we should note first is that light bleaching or burning may look like nitrogen deficiencies. The key difference between the two is that light burn or bleaching will occur on the leaves of the plant closest to the light, whereas a nitrogen deficiency is something you’ll see from top to bottom. A burned and bleached plant will also have wilted and discolored top leaves that are hard to pluck, whereas a deficiency will make the leaves simply fall off. Light Bleaching- If you use LED’s you may not stress your plants from heat, but hanging your LED’s too close to your plants will bleach your leaves. If you let it go on longer, it’ll eventually start bleaching fruits and flowers, which will result in an underwhelming yield. Heat Stress & Bleaching- HID grow lights pose a threat on both ends. Not only will hanging them too close to your plants bleach them, but the environment around the plant will start to overheat the plant. This will cause the plant to dry out and curl, which means they are thirsty (NOTE: in nature, leaves curl and turn up to collect moisture and let it flow down toward the plant’s roots) In cases of bleaching, you simply want to move your lights further away from the plant. They may not ever get back that color you love, but you can prevent it from ruining your crop. In terms of heat stress not only do you want to consider moving and adjusting your lights, but you’ll want to regulate the temperature in your grow room. That means installing a new source of cool air, airflow, and making sure your medium is at a good temperature (some growers forget that roots also need a cool temperature to help against overheating)
Transplant Shock Will Stress Your Plants
Moving your plants through various grow pots or mediums can be dangerous if it's done incorrectly, with stagnant growth being the least of your problems, and total death of the plant being the worse. Photo: Organic Gardening News and Info
Transplant Shock- If you only experience stagnant growth with color instead of no growth and fading or lightening in color, that usually means that though your plant is stressing out, it’s still growing. This is usually the case for plants that have been transplanted into a different container after it’s been root bound in a smaller one. Some root-bound plants you can simply loosen the roots of before transplanting, or simply plant them and assure roots have room to stretch out. Severely root-bound plants will require you to physically cut through the roots for the plant to have a chance at growing new ones. This, though, isn't too bad of a process because roots are great at building new networks from old ones- they just need the room. Nutrient Shock- Now if your newly transplanted plant's roots are fine but it has stopped growing, or it begins to shrivel and collapse, you've got a nutrient stressor. The most common reason a plant starts to die shortly after transplant is nutrient shock. Your plant was used to all the nutrients at a certain pH level at one point in its life, but all of a sudden there's a pH spike in the new solution. That spike will begin to essentially poison your plant if not attended to quickly, but at that point, you may have already gotten rid of it. A smooth nutrient transition is necessary to keep plants alive, no matter if it's a soil or soil-less plant. If your plant isn't ready for the feeding you're going to give it- or if you give it a feeding you didn't mean to- get ready to work getting it back on track. We should also note that things like root rot will also stagnate your grow, whether it's from overfeeding your soil plants or not preparing your hydroponic medium and solutions when transplanting.
Other Factors That Stress Your Plants
Growers know that giving your plants too little or too much water can ruin them. That's a no-brainer at this point. But if you think you're giving your plants the right amount of water and something's not right- say they're drooping and dark, or curved and discolored- they could be telling you something about your growing conditions.
Overfeeding Soil-Grown Plants- Soil growers can oftentimes forget that soil takes longer to process nutrients that a hydro garden, so they may feed their garden more often than they should. With enough heat and not enough tilling, overfeeding your plants can cause soil to compact, which will keep your plants from receiving any water at their roots. While you think you're watering your plants, you're just making more clay that water can't penetrate to feed them. Overdoing CO2 in the Grow Room- A lot of hydro growers boost the production of plants by adding Co2 into their grow, which makes the metabolism of the plant speed up to grow. If you've added Co2 into your grow, kept the same feeding schedule, but your plants look a little dry, they may not be getting enough water- they're sweating too much and not eating enough to compensate. On the opposite end, if your plants are starting to droop when you add Co2 it's likely because they're not able to process the water they're receiving fast enough to let it out and take in more. Instead, the plants leaves become heavy, droop, and begin to die off. There are a lot of things that will stress your plants: the environment they grow in, the lights they grow under, the food they receive, etc... So keep an eye on your plants and your garden's equipment. Your plants will tell you if something's up because just like us, they'll get stressed when they're struggling to survive.