Houseplants Under Lights

Lesson 3: Watering, Humidity and Fertilizing

HUMIDITY & PH

Humidity

Humidity is the amount of water vapor in the air. Warm air holds more water than dry air. Most heated homes have very low humidity levels. The plants may show signs of stress similar to those listed for too little water. Low humidity may also lead to problems with spider mites that are discussed in a later lesson.

There are some easy ways to raise the humidity around the plants. You can use a cool water humidifier (available in anything from gallon size to room size). Grouping the plants together will help create humidity in their immediate vicinity. Sitting planters on trays of gravel with water just below the top of the gravel will also help this problem. Sometimes the best solution is simply to grow plants that don't need high humidity levels.

What is pH? How does it affect my plants?

There are two factors that influence the success of anything you plant. These are the pH of your soil and the amount of nutrients available in the potting media. If the pH is either too high or too low, certain nutrients may not be available to the plants even though they are present in adequate quantities in the media.

What is pH? It is a measure of the amount of hydrogen ions available in the media. This is measured on a scale of 0 to 14 with 6 7 being considered neutral. Below 6 indicates an acidic media and above 7 indicates an alkaline media. Most houseplants and succulents prefer a neutral pH. Therefore, either acidic or alkaline media will need to have their pH adjusted.

What causes a low pH problem? Medias based mostly on peat will have a low pH because peat is naturally acidic. On rare occasions, your water may be too acidic.

What causes a high pH problem? The chief reason for a high pH problem in soilless media is the quality of your water -- whether it is from your own well or provided by the local utility company. Some water providers are purposely using alkaline water because it doesn't clog up pipes as quickly as acidic water can. On the other hand you may have neutral water that when combined with a peat-based potting media, results in an acidic potting media.

How Do You Solve These Problems?

Indoor gardeners can test the pH of their media and change it easily. First, fill a container with your potting media. Then soak it with water. Keep some of the water that drains from the media. Using a pH testing kit meant for aquarium keepers, follow the directions on the bottle and check the pH of the water you drained off the test pot. If it tests in the acidic range, buy some of the liquid aquarium keepers use to raise the pH; alternatively, if the test result is alkaline, buy the liquid fish keepers use to lower pH. Follow the directions on the bottle of either product.

Some people use vinegar in a gallon of water to lower the pH of water. If you choose this route, you'll still have to test your water. Then you have to experiment to see just how much vinegar you need to add to bring the water into the neutral pH range.

The best solution is to use your pH meter to test both your water and your potting media. Each meter provides a set of instructions on use. Be sure to follow those instructions carefully for accurate results.

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