If the plant only has one or two yellow leaves, or if the yellow leaves are older growth beneath new growth, there is nothing to be worried about. Plants and their constituent parts have lifespans, new growth replaces old growth and old growth dies away. Normally this happens so quickly that the death of old growth isn’t noticeable.
If large portions of the plant (especially new growth) are turning a lighter color green, or if the leaves have begun to turn yellow, the water-nutrient combination in your pot is probably out of balance. The usual causes of leaf yellowing are:
1) too much water and/or
2) too little fertilizer.
1) Do you consistently add water to the reservoir before it’s empty?
2) In addition to filling the reservoir, is the Gro-System regularly watered on top by sprinklers?
3) Do you fertilize less often than once a week?
4) Are you fertilizing once a week, but the leaves are still yellowing?
The most common mistake most Gro-System beginners make is over-watering their plants. If water is added to the reservoir before the dipstick shows the previous level has dropped to 1/4” or less (ie. keeping the reservoir “topped off”), the plants may be getting too much water. If automatic sprinklers regularly soak the Gro-System pot, they are almost certainly getting over-watered.
Plants need to breathe (aka. aerate). Over-watering causes root damage (like rot), which prevents plants from absorbing needed nutrients. Damaged roots also open doors to other plant diseases (like Pithium Fungus, Powdery Mildew, and various viruses). To enable root aeration, it is crucial to allow the water in the reservoir to empty regularly (at least every 4 days or so). We have included a dipstick with each Gro-System pot to make it easier to tell when it’s watering time. Using the dipstick is like checking the oil level in a car, simply:
1) insert the dipstick down the fill tube until it hits the bottom of the pot,
2) remove the dipstick,
3) check the wet mark on the end.
Although the “add water” level will vary depending on the plant’s changing needs, at the beginning of the season, it’s best to let the reservoir level drop to 1/4” or less showing on the dipstick. For complete instructions on watering, see “Watering Instructions”. If your Gro-System has been over-watered, see “Treatment for Over-Watering”.
Unlike plants in the ground, which obtain most of their nutrients from the soil, potted plants depend almost entirely on added fertilizer. The liquid Gro-System fertilizer that comes with each pot is formulated to induce vigorous growth throughout the whole growing season. Apply it regularly (about every third watering) to keep the nutrient level in your Gro-System balanced. For complete instructions on fertilizing, see “Fertilizing Instructions”. If your Gro-System has been under-fertilized, see “Treatment for Under-Fertilizing”.