Watering, Humidity, and Fertilizing
To check the water content in potting media, air humidity, and the pH of both potting media and water. Tools: humidity meter, water meter (if desired), pH meter, bamboo skewers (used for kabobs)
Water, humidity, and pH of potting media and/or water used for watering all have an effect on the growth of your plant. Your plant will have a preference for the amount of water in its potting media. Plants also have differing needs for humidity in the atmosphere. Some plants want a humid atmosphere (humidity = amount of water held in the air at varying temperatures. Warm air holds more humidity than cold air.) Most fern species prefer high humidity while most cactus and succulents prefer little or no humidity. The pH of the water and potting media will be discussed below.
Water is essential for all plants including succulents. The amount of water used by a plant will vary widely. Some plants want to grow in nearly 100% water (aquarium plants) while others want minimal water (cactus and succulents). If you show an unidentified plant to a professional grower and ask how often you should water it, you will usually receive the answer “it all depends”. Although this sounds like an evasive answer, the truth is you must know the proper identification of a plant in order to know where it grows naturally and what the average humidity is in its natural home.
Recognizing watering problems can be difficult. Take special note that plants growing under lights receive optimal quantities of light each day. This means the plant doesn’t change its watering needs from season to season. It also means you have total control over the quantity and quality of water received by your plant. Here are some general signs of under-watering and over-watering.
Signs of under-watering
If the plant is wilted, feel the soil. Most wilted plants will have bone-dry soil. Check your potting media. Water most plants if the media is dry to the touch. Succulent leaves or stems begin wrinkling when the plant needs additional water. You can often tell a plant needs watering just by lifting the pot. If it is lighter than usual, water the plant.
Signs of over-watering
Look at your potting media. Is it soggy? Does it have a rotten smell? These are signs of too-wet-potting media. Do the roots look mushy? This means the roots aren’t getting adequate oxygen because the pores in the potting media are filled with water. If this happens, take the plant out of the pot (complete with potting media) and set it on a newspaper to absorb excess water. Then trim the roots back to those that still appear healthy and re-pot.
If the plant stems look mushy or have a rotting smell, the plant is suffering either from over-watering or from a disease. Unpot the plant and trim it back to a healthy portion. Use the healthy portion to restart the plant following instructions given in the lesson on purchasing and transplanting houseplants.
HUMIDITY & PH
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 number 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 number of hydrogen ions available in the media. This is measured on a scale of 0 to 14 with 6 and 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? Media 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 in 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 the pH. Follow the directions on the bottle of either product.
Some people use vinegar in a gallon of water to lower the pH of the 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.
Indoor Plant Lighting
Natural lighting vs. Artificial Lighting
Proper lighting is critical for good plant growth. This can be provided naturally (via windows, skylights) or artificially (light stands, plant lights).
1. Identify potential locations in your home for plants.
2. Measure the light levels available by using a light meter.
3. Determine which type of supplemental lighting is most suitable for your needs (both function and aesthetics).
4. Determine if you will use existing shelves, tables, etc. or if you will purchase a professional light cart or make your own.
Supplies: Light meter (Varies in price depending on your source.) Typical prices range from $9.95 to $29.95 with prices indicating the quality and life expectancy of the meter. I strongly advise you to purchase the best you can afford. A light meter is the only way you can be sure of the quantity of light your plants receive.
Plants need light to grow indoors. It is up to us to provide the appropriate light. The amount required is determined by where the plant grows naturally outdoors. Forest floor dwellers obviously need less light than those growing in full sun.
The easiest way to determine the amount of light a plant will receive in a specific location is to purchase a light meter. Each meter measures slightly differently. Read the directions carefully to determine how to interpret the information provided by your light meter.
Example: My light meter shows foot candles. [A “foot candle” is the amount of light a candle gives off one foot from the flame.] Less expensive meters usually just indicate “low,” “medium,” or “high.” For the purposes of this class, low lighting is 1,000 to 1,500-foot candles; medium lighting is 1,500 to 2,500-foot candles, and high lighting is 2,500 or higher-foot candles.
Here is generalized information regarding the amount of light available for windows facing different directions. It is important to check the actual light conditions with some type of light meter.
North windows. A window facing north usually provides semi-shade or shade conditions for plants growing directly on the windowsills. The presence of trees, buildings, or roof overhangs limits the light coming through the window If there is enough light to read by, you may generally use any shade-loving plant in that location.
East windows. These windows receive direct sun only in the morning. This is a good location for flowering plants requiring low to medium light levels.
South windows. This is an excellent location for plants needing high light levels. Some plants may even burn if the window is not shaded with a sheer drapery or partially closed blinds. This location can be hot in the summer.
West windows. This window provides high light levels, particularly in the afternoon. Shading may be required for some plants. This location can be excessively hot in the summer.
Supplemental lights are the easiest way to overcome the lack of natural lighting. There are many types of lights available for indoor gardeners. The various types of light bulbs emit different wavelengths on the light spectrum. The light wave spectrum ranges from ultraviolet to infrared (the orange and red ends of the spectrum). The visible portion of the light spectrum is from violet to red. These are the colors that we can see. Plants may be harmed by ultraviolet light that, fortunately, is screened out by most glass.
Plants need the full range of the visible light spectrum for successful photosynthesis. Photosynthesis is the process that turns carbon dioxide, water, and light into the carbohydrates used by the plant. These carbohydrates are further processed into the various compounds needed by a plant for growth.
The distance between the light and the plant determines the amount of light energy actually received by the plant. More light is received when the lights and plants are a short distance apart. You will prove this using your light meter.
What Light Bulbs are Available to the Indoor Gardener?
The three most commonly available lights for the indoor gardener are incandescent, fluorescent, and halogen. The advantages and disadvantages of each of these are discussed below.
Incandescent: These are the light bulbs we use in lamps and other lighting fixtures. Benefits: Low cost. Disadvantages: High heat output, poor light quality (for growth purposes), low efficiency in using electricity, and short life span.
Fluorescent lights: Available as cool white or warm white bulbs.
Benefits: Low cost, cool running, better balance of light, and longer life span. Disadvantages: Light intensity decreases from the middle of the bulb to the end of the bulb, may need to balance the available light spectrum by combining cool and warm light bulbs for flowering plants, and low efficiency in the use of electricity.
NOTE: Many fluorescent lights are now 25 or 34 watts instead of the traditional 40 watts. Look for 40-watt bulbs.
Halogen Lights: These lights are rapidly becoming common in shop light fixtures and lamps. They normally come in 150 and 300-watt bulbs.
Benefits: Readily available, provide pleasing white light similar to natural light, provides full light spectrum for plant growth, provides a higher level of foot-candles per unit of electricity used than other bulbs.
Disadvantages: Low efficiency in using electricity, the medium life span of bulbs, and the cost of bulbs.
Visit hydroponics or an indoor gardening store. They have many additional types of lights available. The reason I am not discussing them is that the majority require expensive special equipment. Some even require having heavy-duty electrical outlets installed. If you are interested in exploring these alternatives, please talk to the store salespeople for guidance.
What Do I Recommend?
After experimenting with different light bulbs, I’ve concluded that the majority of foliage plants grow well under cool white shop lights. The only plants that do not grow well in these conditions are the cactti and succulents that demand bright, western sunlight to thrive and flower.
Therefore, I have chosen not to grow succulents needing higher light levels. I use a two-bulb fixture for plants requiring low to medium lighting and a four-bulb fixture for those needing higher light intensity.