Plant Health: Watering and Nutrient Deficiencies Explained

A look at common watering problems and nutrient deficiencies

This time of year, plants can start looking pretty shabby. It’s hot out and many are reaching the end of their life cycles. It may look like your plants aren’t getting enough water or need a boost of compost, but really what’s happening is that they are putting all of their energy towards making seeds, which leaves the foliage looking less vibrant and the entire plant just a little…well…bleh. When plants start to look like this many people make the mistake of increasing their water schedule or fertilizing a bunch. During this time, it’s best too keep your watering and fertilizer schedules the same as usual. But then how can you tell when your plant isn’t getting the proper amount of water or nutrients? Here are a few helpful tips to guide you through troubleshooting water and nutrient issues.

Water-too much, too little, just enough

When a plant isn’t getting enough water it will tell you with sad, drooping leaves. In botany, when we talk about a plant being turgid, it means the plant is upright, stiff, and has enough water. The plant loses this turgidity and begins to wilt when the water has transpired and not been replenished. The leaves will lose their stiffness, and begin to droop and shrivel up. You may be watering your plant as suggested, but it still looks thirsty. In this case, your soil may be too well drained. Adding water holding mediums to your soil such as perlite, vermiculite, or coir can help your soil get more water to your plants. It is a good idea to add a drip irrigation system on a timer to ensure that your plants are getting regular water. You can set your timer to water as much or as little as your plants need.

It is a bit more difficult to tell when a plant is being over-watered, as it can sometimes resemble nutrient deficiency, or even under-watering. A plant that is over-watered will droop, just like an under watered plant. It may also have leaves that are yellowing, or soil that is turning green with algae. If you take a plant out of its pot and inspect its roots, an over-watered plants roots will be brown, and gray, instead of white. This is called root rot and it is caused by a plant not getting enough oxygen because it is literally drowning in too much water. Also, an over-watered plant’s leaves may get brown patches and drop from the stem prematurely. Oftentimes plants become over-watered when their caretakers are too attentive. Before you water, check the soil to see if it is still wet. If so, don’t water yet. Plants can also become over-watered when there is a drainage problem. If your soil has too much clay in it, it probably isn’t draining well. In this case, add some aerating mediums to your soil, such as bark, coir, or perlite. Again, when it comes to water issues, a drip system on a timer is the way to go.

Nutrient deficiencies

This is a topic we could spend an entire semester on (as I have). Let’s very lightly brush the basics of plant nutrient deficiencies and we will focus on the macronutrients only: Nitrogen (N), Phosphorus (P), and Potassium (K).

Nitrogen helps with plant growth, foliage quality, and is a part of chlorophyll, the green pigment of the plant. You can tell a plant is Nitrogen deficient when it’s leaves turn yellow, usually in the older leaves first. If your plant seems to be growing too slowly, it also may have a Nitrogen deficiency. Here is a picture of what a plant looks like when it is lacking the proper amount of Nitrogen:


Yellowing on corn leaves caused by nitrogen deficiency

Yellowing on corn leaves caused by nitrogen deficiency

Phosphorus helps a plant withstand stress, is involved in the formations of sugars, oils, and starches, and encourages blooming and root growth. You can tell if a plant needs supplemental Phosphorus when the tips of its leaves start looking burnt and older leaves turn a dark green or purplish color.

Phosphorous deficiency in a corn plant

Phosphorous deficiency in a corn plant

Potassium’s specialty is aiding in fruit quality and warding off disease. When a plant doesn’t have the proper amount of potassium it’s leaf tips may curl inward and be scorched. There may be yellowing in between the leaf veins, and purple spots might show up on the under side of the leaves. If your plant or root growth is stunted or it isn’t producing any fruit or any seeds, your plants might be Potassium deficient. Here is a picture of what it might look like:

Potassium deficient soybean leaf

Potassium deficient soybean leaf

Plants should be getting enough nutrients from your soil, especially if you plant natives, but if you are having issues with plants looking nutrient deficient, it could be a pH problem, or you might need to replenish your soil with compost or an organic fertilizer. We don’t recommend using chemical fertilizers as these usually lead to plants getting weak over time, salt buildup in the soil, and toxic runoff into our water.

Hopefully this info will aid you in determining whether or not it is time to increase or decrease water supply, or add some food to your soil. As our Summer slowly turns into Fall, we lose all of that vibrant color from flowers and veggies, and instead get our visual kicks from those gorgeous deciduous trees. Won’t be too far away and I’m looking forward to it, well.. all but the raking part… 🙂


Image attribution:

Mary Ann Hansen, Virginia Polytechnic Institute and State University,

Daren Mueller, Iowa State University,

Felix Francis, University of Delaware,