Root Problems in Cucumber Seedlings

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Root problems are a common issue facing growers in any type of growing system. While not easy to spot, when the plant starts showing signs of problems, it’s usually too late to correct. In this article, we’ll show some examples of young cucumber seedlings afflicted with root disease and examine the reasons why it occurred.


Root rot occurs when the roots of a vegetable plant die off due to a combination of heat, moisture, humidity, and lack of oxygen. Healthy roots are white, strong, and firm. When roots are rotting, they look off-white/brown, have a slimy and mushy texture, and tear off easily. The presence of mold and fungus is also possible. When plants are afflicted by root problems, it’s usually too late to save the plant and the necessary precautions are necessary to dispose or sterilize the media before using again.


Pythium is one of the most common organisms that causes vegetable plants to damp-off and causes crown and stem rot. In cucumbers, it will make the stem look “pinched” and the leaves will appear wilted. They are fungal-like organisms that produce spores called oospores and zoospores. Pythium causes the stem to look dehydrated, thereby not allowing the top side of the plant to receive water and nutrients. There are many remedial fungicides available in the market but the best way to treat pythium is by preventing the occurrence of an attack.

Stem is pinched and gradually affects the whole crown of the plant

Stem is pinched and gradually affects the whole crown of the plant


Pythium shows up when the grow media is wet and hot. The combination of excessive watering, poorly drained grow media, and high environmental temperature causes major root problems in the rootzone. This makes for a very favorable humid environment for pythium and other classes of fungal organisms to attack the rootzone. Here are some afflicted cucumber seedlings planted in cocopeat. The seedlings were irrigated too frequently and the grow media was “wet” instead of moist all throughout the day. While cocopeat is an excellent grow media due to its organic properties and porous nature, it simply couldn’t drain as much water as fast as it received more water. Avoid overwatering and ensure your grow media is a good porous mixture that can drain and dry up over the course of the day.

10 day old seedlings topping over due to Pythium

Seedling looks healthy on the top but there’s problems in the rootzone


The best grow media mixtures in hot climates such as the Philippines is one that is able to absorb and retain a nutrient solution while porous enough to allow water to drain out. Root problems starts with water-logging so that’s why water must be able to drain freely over the course of the day. It takes time and practice to get comfortable with using the different types of grow media mixtures in different seasonal periods but that’s all part of the fun of being a grower.

Our preferred mixture during hot seasonal weather is cocopeat, perlite, and hydroton.


In hydroponics, it is essential to maintain a low nutrient solution temperature. High nutrient solution temperatures means less dissolved oxygen is available in the solution therefore the roots will not receive enough oxygen to “breathe”. In container-type of grow systems (NFT & Dutch Buckets), the air inside the chamber can heat up and causes unwanted condensation which can restrict the airflow of the roots. It’s essential to let the roots “breathe” and avoid high temperatures and humidity to accumulate in the container. Adding air bubblers into the reservoir also helps in maintaining oxygen levels in the nutrient solution. Also, since pythium produces and releases zoospores into the nutrient solution, it is good practice to change out nutrients in the water reservoir regularly.


There are a host of fungicidal solutions to help treat affected plants but none of it will be effective unless a grower resolves the root cause of the problem. By closely monitoring plants and setting irrigation timers according to the needs of the plants based on the seasonal temperatures, a grower can avoid the occurrence of root problems. Often times, it’s easy to forget that oxygen (in the rootzone) is one of the main elements necessary for a plant to thrive, so a grower needs to be mindful of the amount of watering based on the profile of the grow media mixture used during the different seasonal temperatures.

Healthy seedling with emerging roots due to the porous nature of grow media mixture and adequate irrigation intervals

Four seedlings per Dutch Bucket without the use of lids to avoid accumulation of high temp/humidity in the chamber.