There's nothing worse than knowing your plant has a problem, but not knowing what the problem is so you can't fix it.
There's a lot of problems that can hit your plants throughout a growth cycle, from bugs to mold to nutrient deficiencies. While bugs and mold can be pretty easy to spot but a major pain to deal with, nutrient deficiencies are also easy to spot, but a little easier to deal with.
So good news! If you think you have a nutrient deficiency, you just have to figure out what it is and then the fix should be easy. The hard part though, is figuring out which deficiency you have!
Essential Plant Nutrients
When it comes to the nutrients that plants absolutely need to survive, there's three: nitrogen, phosphorus and potassium. While nitrogen and potassium are important during the early stages of growth, phosphorus is essential for a strong flowering stage that produces healthy yields.
But all three nutrients (NPK) work together throughout the plants entire lifecycle, and when your plant is missing one for too long, it will let you know. NPK might be essential, but there are some other nutrients that plants might need supplemented, like calcium, magnesium or iron.
Mobile vs Immobile Nutrients and Deficiencies
Plant nutrients and plant deficiencies come in two forms: mobile and immobile. Mobile nutrients can be utilized throughout the plant after it is taken in, and immobile nutrients stick around where they are deposited without much movement.
As for the deficiencies, a mobile deficiency will show symptoms in the older leaves at the base of the plant. An immobile deficiency will show itself in the newer growth at the top and outer branches of the plant.
Now we can get in to how to spot specific deficiencies.
Nitrogen deficiency is the most common, mainly because it is essential throughout the lifecycle of the plant, but especially during vegetative growth.
Because nitrogen is a mobile nutrient, a nitrogen deficiency will show itself first through yellowing in the older leaves of your plant, most likely near the base.
Without a fix, the yellowing will spread from the base up and eventually cause browning.
Potassium is also essential during early plant growth. It is a key factor in the process of cell division as well as transpiration, root growth, and water uptake. Just like nitrogen, plants can't grow without potassium.
If your leaves look greener than normal but also a little dull, that could be a warning sign of potassium deficiency. Next your leaf tips might begin to look like they are slightly burnt, plus additional yellowing similar to nitrogen deficiency.
Without intervention, your plants will experience dehydration, leaf burn, and curling of younger leaves, resulting in extremely weak plants more susceptible to disease.
Phosphorous is essential for photosynthesis and the release of stored energy in your plants. Phosphorus deficiency is less common than nitrogen and potassium deficiencies, but it can be just as damaging.
Most commonly caused by pH surpassing 7.0, your plants will first start showing a phosphorus deficiency through the purpling of leaf stems. The leaves will slowly take on a darker, almost blueish hue and the deficiency will continue to spread.
Eventually growth will slow drastically in your plants, and dark spots will develop on your leaves as they begin to curl and fall off. With growth being inhibited so drastically, a phosphorus deficiency can completely ruin a harvest.
Fixing the Deficiency
The good news when it comes to fixing a deficiency is that you know exactly what your plant needs. If you have a nitrogen deficiency, give your plant some more nitrogen, same with potassium and phosphorus.
Over time your plants will usually bounce back. However be careful when you start feeding to fix a deficiency. Giving your plant too much of a nutrient too fast in an effort to solve the problem more quickly might actually cause you more problems.
If you want to know about nutrient lockout and how that can damage your plants, read our guide on what nutrient lockout is and how to fix it!