Basil leaves died because of downy mildew

9 Reasons Why Hydroponic Basil Wilt

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Basil grows quickly with minimal care and sometimes takes over the entire garden in hot and humid conditions. Thus, it is a perfect herb for beginners to grow. You’d hardly go wrong with basil.

Yet, some mistakes can kill any plant, and basil is no exception. The most common symptom Basils show is wilting. This post is about such mistakes.

Our focus is on hydroponically grown basil, but soil-grown basil isn’t very different. You could also use most of the tips we recommend for soil-grown basil.

There are many hydroponic systems. Most plants grow well in one system and don’t in others, and some plants are not feasible to grow in specific systems. For instance, it isn’t easy to grow carrots in NFT systems. But basil doesn’t have preferences. It grows in almost any hydroponic system. Basil grows in Kratky just as well as in NFT.

Here are the top 7 reasons you see wilt in hydroponic basil.

1. Lack of sunlight

This is the prevalent reason for basil’s wilting and slow growth. Most gardeners easily overlook this factor, but basil loves sunny and humid conditions to propagate and grow.

Often, before wilting, the leaves turn yellow. You’d see the yellowing everywhere in the plant. The purple and red varieties won’t change their color in low sunlight. They remain pale before they die.

The fix for this one is very obvious. Move the plant to a sunny area of your garden. This is easy if you’re growing in single-plant Kratky buckets. Yet, hydroponics systems designed to grow many plants aren’t very supportive. For instance, if you have many long NFT channels, moving them to a different place is a hassle.

If you’re growing indoors, move the basil plant closer to a window where it can receive at least 6 hours of sun exposure. If you’re growing with grow lights, install more or some reflectors to make the most of the available lights.

Related: How Much Light Does Basil Need?

2. Heat stress

On the opposite spectrum of the same factor, basil can also wilt due to heat stress. Although basil has evolved to handle excessive sun, sometimes excessive sunlight turns the leaves dry and wilt.

Wilt due to heat stress doesn’t happen overnight, and it’s pretty easy to spot. The plants show symptoms only when under the sun; they look perfectly normal in the evening and morning.

The fix for heat stress is also easy: Install a shade net over the basil plant. Yet, moving to a shady area wouldn’t be a good idea, as basil still needs a good amount of sunlight to grow.

Indoor hydroponic growers rarely experience heat stress. If you do, move the grow light a little farther or dim the lights slightly.

3. Insufficient airflow

airflow is essential for any crop you’re growing. Airflow helps the plant uptake more nutrients as it aids transpiration. Certain nutrients like calcium need airflow to help them get to the tips of the leaves. Without enough airflow, the leaf tips would start to burn. Eventually, the entire plant would wilt and die.

Often, hydroponic growers prefer a controlled environment. In a closed environment, airflow could be lower than outside. This is also true for indoor hydroponic gardeners. If using an indoor hydroponic kit, you must ensure that your chosen area has enough airflow.

You can fix this with the help of a fan. Install them so they can circulate air throughout your growing area.

Related: The surprising cause of tip burns in lettuce

4. Nutrient deficiency

Nutrient deficiency is a common issue for hydroponic basil. Often, people grow basil with lettuce as a companion plant. Lettuce needs about 0.8 -1.5 EC, yet basil grows well on nutrient concentrations of 1.5-2.5 EC. This is a common reason for basil’s wilt.

Basil rarely has an issue with the nutrient mix. You can use any hydroponic nutrient solution, and basil will happily grow. Yet, if you don’t supplement with calcium nitrate, that is, if you’re using a single-part hydroponic nutrient solution, you might want to choose one with a high nitrogen percentage.

You could folier feed basil with specific nutrient solutions. Yet, you must correctly identify whether it’s a nutrient problem and which nutrients the plant lacks. This is for a future post.

5. Diseases

Basil is a very resilient plant, but it can also catch diseases. The most common infections for basil are downy mildew and fusarium wilt, both of which cause the plant to wilt. The most common reason for these diseases is insufficient airflow, which we discussed in a previous section.

Basil leave with downy mildew symptoms starting to wilt

Besides the lack of airflow, infections happen when your tools aren’t clean. For instance, if you harvest basil with an infection and use the same pruning scissors without cleaning it, the next one may get the infection.

Related: 7 Tips to Avoid downy mildew in basil

6. Pests

Once again, basil is grown along with other plants because of its repelling effect on specific pests. But that doesn’t mean basil is immune to every kind of pest. Basil is still vulnerable to aphids, leafminer insects, and other pests.

Protecting plants from pests is a topic for a separate blog post. Yet growing basil inside a controlled environment is a no-brainer. Installing insect nets around the basil plants would make a huge difference. By blocking most of these insects, you not only diminish the direct risk from them, but sometimes, these little creatures bring other more severe pests and diseases to the plant.

A simpler alternative is to cover the plants with an insect mesh. It’s cheap and effective in controlling some pests.

Lastly, you could try some pesticides. You may opt for an organic pesticide like neem oil to eliminate some common pests like aphids.

Related: Hydroponic Basil Pests and Diseases

7. Low water level

A prevalent hydroponic basil mistake is the low water level. Significantly, if you’re growing in passive systems like Kratky or Wick hydroponic systems, you may forget to check the water level.

As the plant grows, its water uptake also accelerates. A seedling doesn’t drink much water in a day, but a fully grown plant may use a lot of nutrient solution daily. Often, people refer to Kratky and Wick systems as set-it-and-forget-it. Unfortunately, this statement is only partially true.

You may check the water level at regular intervals, but a better approach is to use a gravity-feeding central reservoir. For example, you may use an IBC tank as a larger nutrient reservoir. Connect this reservoir to your Kratky system container. Use a floating valve to set the water level. The floating valve will open and refill nutrients as the water level decreases.

At low water levels, any plant will wither and die. Basil, too, will experience the same fatality.

8. Root rot

Like low watering levels, too much water is also an issue for basil. When the water level is too high, basil often gets root rots.

Once again, this is prevalent in passive systems like Kratky. DWC and systems circulating nutrients are reasonable solutions to prevent root rot, as there’s more oxygen in the water than in Kratky. Yet, if you’re growing basil in Kratky systems, you must ensure that there are at least 3-6 inches of roots above the nutrient level.

It’s a critical problem in outdoor hydroponics. Rainwater may enter the container through the growing medium and raise the water level if it rains. You must check the water level after every storm if you’re growing basil or any other plant in outdoor Kratky hydroponic systems.

Related: Fixing Root Rot in Hydroponic Basil

9. Inappropriate growing medium

The selection of a growing medium plays a pivotal role in hydroponics success. Factors like water retention capacity, pH, and EC of the growing medium all impact the plant’s health.

Basil loves slightly acidic soil or growing medium. Of course, most plants love to grow in the 6-6.5 pH range, and basil would thrive in this range.

Growing mediums like coco peat and oasis cubes are pH neutral. Thus, the pH of the nutrient solution itself is taken into account. Checking the pH of the nutrient solution is often sufficient if you’re using these as your growing medium.

Contrarily, if you’re growing with rock wool, it’s alkaline. This may cause wilt in basil, and eventually, the leaves will dry up and fall off. You need to adjust the pH first to get the optimal results.


Basil is a favorite herb in several cooking styles around the world. It’s also one of the easiest to grow in hydroponics and soil. Yet, there are instances where basil withers and dies. There are several reasons why basil wilts, but we’ve discussed eight widespread reasons in this post. One of these is almost always why your basil’s health is impaired.

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