I remember walking into a hydro shop for the first time years ago and feeling overwhelmed at the amount of equipment and products involved in growing cannabis. Then, after I encountered my first real problems, I started asking questions. I was almost always told that pH lockout was the culprit.

Fast forward a number of years, after being a hydro store worker and manager, and now a product specialist for a leading nutrient company, I’m here to detail for you the most common real-world problems you’ll face. And I can tell you: it’s rarely pH lockout.

pH Lockout in Cannabis Plants

OK, sometimes it is actually pH lockout. In the realm of indoor gardening, pH works as a sort of sliding scale of nutrient availability. The scale runs from 0 (most acidic) to 14 (most alkaline).

In hydroponic gardening, a pH in the 5-6 range is optimal for most plants. In this range, the minerals plants need are in the best compromise of availability while also being in an acceptable environment for the plants to flourish.

Nutrient lockout occurs when a substantial, prolonged change in pH occurs. As the conditions slide too far towards the acidic or alkaline sides of the pH scale, plants are no longer able to uptake adequate amounts of the 13 minerals they need from fertilizers.

Due to this inability to uptake specific minerals, depending on the degree of the pH swing, plants will show signs of deficiency for the various minerals they are unable to absorb. Typically, if you’re experiencing true pH lockout, you are in one of the following situations:

  • You’re watering in nutrients on top of a potting mix and complications develop. Contact your soil and nutrient manufacturers to ensure the products you’re using are compatible. Sometimes modifications are needed.
  • You are using a homemade potting mix with ingredients that influence the nutrient solution in a substantial way. A typical source of this is compost that has not finished decomposing. If the compost is still decomposing, it can make the soil unstable. A lack of lime or similar buffering ingredients, or an imbalance of added amendments, can also be causes.
  • You’re using a recirculating hydroponic system. In recirculating systems, everything moves faster, and constant pH fluctuations may be attributed to contamination in the form of light getting into the system, enabling bacterial growths. Organic-based products containing particulate matter can be forced into crevices by the movement of the solution. These organic deposits can also give off compounds as the conditions break the solution down. Such secretions, if unchecked, can cause prolonged periods of extreme pH fluctuation.

In the scenarios mentioned above, regular maintenance and habitual pH monitoring can prevent unfavorable conditions from lasting long enough to cause pH lockout. With that out of the way, let’s move on to the things that can go wrong in the growroom that pH lockout commonly gets blamed for.

Overwatering Cannabis

Overwatering is the most commonly overlooked problem in the growroom. Different growing mediums require different amounts of nutrient solution to be adequately saturated, and spacing those feedings properly is a key skill you must learn to be a successful grower.

Providing the right amount of oxygen to the roots is essential to achieving maximum yields. Here’s a breakdown of overwatering situations by growing medium:

  • In hydroponics, plants sit in water, but the water must be aerated properly. If the solution goes stagnant, your plants could drown. Check your system’s water and air pumps to make sure all is well.
  • Potting soil contains compost, which is quite dense and can easily turn into a brick sitting on your plants’ roots. If this occurs, water less often.
  • Soilless mediums are often mixtures of peat, coco, perlite and other inert ingredients, and different mixes have varying water-holding capacities. In an indoor setting, you may not need a mix with the maximum water-holding capacity level. Like certain potting soils, soilless mediums can get heavy when over-saturated. Providing plants with less feed more often may be the trick.
  • A final tip for growing in potting soils or soilless mediums is that you want the medium to be saturated, but not overly so. Grasp both sides of the pot and pick it up. You’ll be able to feel if the medium is evenly saturated. You don’t need additional feed after this point.

Overfeeding Cannabis

When it comes to nutrients, people often think the more gas, the bigger the bang. But more is not better when it comes to nutrients, and careful management of your feeding schedule is crucial. Here are some common overfeeding situations:

  • You’re feeding nutrients to a plant you’ve just put into potting soil. Hold the nutes! Potting soils most often contain their own source of fertilizer in the form of compost and amendments. The food present in the medium is usually adequate to feed the plant for up to 4-6 weeks, depending on the size of the plant and its container. As the plant signals the start of deficiencies, start feeding at 25-50% of the recommended feeding strength listed by the nutrient manufacturer. You can always go up in strength.
  • You are running high temperatures. If your growroom is on the warm side, your plants take in more fluids and can actually take in too much food, causing discoloration.
  • You are using water with lots of minerals. Depending on where you live, your water may already be saturated with undesirable solids, which makes it harder for plants to take in nutrients. If you do not correct for these levels, plants may be stunted in growth or show signs of deficiencies. This is why many manufacturers sell hard-water formulas or offer charts to modify feeding schedules for these conditions.
  • You are using additives on top of a full nutrient line. Nutrient manufacturers put a lot of work into making feeding schedules. They must be stable, work in a majority of situations and have a largely known outcome with popular growing methods. If you’re using a full line as well as additives, especially flower-bulking additives, you may need to cut out the redundant product. Contact the manufacturer to ensure your products are compatible.

Before you immediately diagnose a complex issue or change up your entire method of growing to fix an issue, start with the basics. Analyze your feeding practices, watering methods, medium type, and environmental conditions. More often than not, modifying a few basic principles will fix problems that at the start seemed much more exotic.