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weed with stalk of red seeds

A standard PH Test Kit has everything you need to test and adjust pH

How exactly does pH affect nutrient absorption?

How to Test and Adjust the PH (full pH tutorial)

5.) Nutrient Deficiency Caused by Lack of Nutrients

These plants were started in nutrient-rich soil, but they used all the nutrients up before harvest. This caused the yellowing leaves and red stems.

In this case, you probably have nothing to worry about as long as you aren’t seeing any other symptoms and plants are growing fast and healthy.

A plant’s roots have the remarkable ability to absorb nutrients from the soil and use them inside the plant. This is accomplished with a complex series of processes, but just to keep things simple for the sake of explaining why pH matters, imagine there are “holes” in the roots that let nutrients in. Now imagine those holes are shaped like circles. When the pH at the roots is in the right range, the nutrients take on the form of circles, which easily pass through the holes into the plant. However, if the pH is too high or low, it actually changes the physical structure of the nutrient molecules. It turns the nutrient molecules into other shapes, for example squares. These squares have a much harder time passing through the round holes. Your plants won’t be able to absorb the nutrients (even though they’re physically “there”) and as a result your plant will experience nutrient deficiencies.

Red stems can also be triggered by keeping a grow light too close to the plants. Regardless of the temperature! Some strains are more sensitive to light stress than others, but just about all plants have a limit when it comes to light levels. It may be surprising, but a plant can experience stress from the light intensity even if the temperature is cool, similar to how a snowboarder can still get sunburned in the cold.

This is a follow up article to a blog that my colleague, Guy Kyser wrote back in 2011 titled “Purple alert: Common Pokeweed”. Since that time, I probably get a dozen or so calls this time of year asking, “what is that huge weed growing in my yard with dark black berries and big green leaves.” Pokeweed!

American pokeweed (Phytolacca americana) is a robust, non-woody shrub that is weedy throughout much of California. Native to the eastern United States from Maine to Wisconsin, south to Texas, Mexico and Florida, pokeweed now occurs throughout much of North America. It is sometimes cultivated as an ornamental or garden vegetable, however more often it’s considered an undesirable weed. Pokeweed is found in riparian areas, oak woodlands, forest edges, fence rows, forest openings, pastures, under power lines, disturbed areas, vineyards, orchards, cultivated fields, parks, and ornamental landscapes.

Pokeweed is spread by seed and new occurrences are often were birds frequent. Monitoring for new seedlings in areas below tree canopies, along fence rows, and below other perches, often provides the best strategy for surveillance and early detection.


Pokeweed is an occasional weed throughout much of the United States and is increasing in abundance in some areas. Once seen as a wildland weed, pokeweed is now becoming more common as an urban and landscape weed. All plant parts, especially the roots, contain numerous saponins and oxalates and can be fatally toxic to humans and livestock when ingested raw or with improper preparations. Severe digestive tract irritations are the primary symptom.