I call this article “Poppy’s House Plant Guide” because I cover most all factors that have an impact on a house plant’s health- lighting, watering, humidity control, air circulation, temperature control, fertilizing, and potting.
Lighting for House Plants
Besides food and water, light is one of the most important needs of plant survival. Light absorbed by plants enable them to convert it’s energy into sugars and starches they need to grow and survive. No light or inadequate light has a detrimental effect on plants.
If we pay attention to our plants, they will tell us if their needs are being met- especially light. Your plant is telling you that it needs more light if it becomes pale or spindly. It will also lean toward the most source of light. Another indicator of not enough light is if a flowering plant fails to produce any flowers or at least weak blooms. Soil in the container will be continually wet which will cause root rot and the plant will slowly die.
The amount of light varies by plant. The best way to know in advance is to take note of the lighting requirements that are usually included with your plant purchase. Variations range from artificial room light to hours of direct sunlight.
A general rule of thumb. Flowering house plants usually require more light than foliage plants.
Seasonal Factors Need to be Considered
We know that the sun is most directly overhead during the summer months and well to the south in the winter. North facing windows receive the least amount of light year round. Southern facing windows gain the most amount of light and heat during the summer months. They continue to receive a significant amount of light in the winter months, but just not as intense (hot).
These seasonal variances make placement of plants very important. You may want to use what I call a dynamic approach to plant placement. The dynamic approach requires that plants be moved during season variations according to light requirements of the specific plants.
The dynamic approach offers the opportunity to be creative. Try using different groupings. Mix in some foliage plants with with flowering plants during the winter in a south window. Then create another display during the summer months.
Window Light Source Tips
South Window Plenty of light year round; great for plants requiring plenty light; exposure provides more area of light.
East Window Considered the best all round exposure; cooler than a west window; warm early morning light; bright light for most of the day; good for both flowering and foliage plants.
West Window Receives warmer afternoon sun and bright light for most of the day; only disadvantage is the possibility of overheating some plants; good for flowering and foliage plants.
North Window No sun, but bright light during the summer: coolest window in the house, especially during the winter(may be drafty as well); for foliage plants mostly.
Meeting plant lighting requirements can be assisted with the use of artificial light. Of course natural light is best, but sometimes a dark corner would be an excellent place for a particular plant. Not all artificial light sources will work however. The incandescent light (regular bulb like a house lamp) is a poor source. They may help if the plant is already receiving some natural light. The best sources of artificial light are fluorescent and halogen lamps. Their output is very near that of natural light and plants do well under them. For best results, ensure the plants get 12 to 14 hours of light. A timer would save you a lot of trouble here. Be careful not to get the light too close to the plant to prevent overheating.
Humidity Control for House Plants
Plants need humidity in order to survive.
Did you know that herbaceous plants need water to stand up? Water to the plant is like air in a balloon. The limp balloon becomes rigid when air is forced into it. An herbaceous plant becomes able to stand up when water fills cells. That is why plants wilt from the lack of water.
Dry air surrounding a plant causes a plant to loose much of its reserve water as it breathes. The more moisture in the air surrounding the plant slows down the amount of moisture escaping. Therefore, it is not only important that the roots have moisture, but the surrounding air as well.
Cactus (succulents) and other plants with thick, waxy, or leathery leaves can tolerate dry air better than others. They store water in their leaves and stems for dry days. Similar to a camel storing water for long treks across the desert.
Plants that have thinner leaves are more susceptible to suffering from the lack of moisture in the air. In other words, the more humidity, the better. I say this with “tongue-in-cheek”, however. High humidity is the breading ground for fungus- don’t over do it!
Once again, pay attention to your plants because their symptoms will tell you if the air is too dry. Curled leaves and dry leaf tips are a good indication of dry air. Dry air can cause flower buds to turn brown and fall off.
An energy efficient home can be a plant’s worst enemy.
Just the average home contains less than 30% humidity! Even lower in some energy efficient homes. Not even good for cactus or other succulents. Deserts have more humidity.
Another factor is the area in which you live. The West/Southwest have areas of very low humidity. Areas of the South and Northeast are known for high humidity. For plants, a relative humidity (amount of moisture in the air) between 50 to 60 percent is ideal.
Another “varmint” for plants is the air conditioning system. In order to cool the home, an air conditioner removes moisture from the air.
How can you raise the humidity?
There are some approaches you can take to add moisture to the air. Use saucers to place the plants in. Fill the saucer with water. The evaporation of the water from the saucer will help add moisture to the air immediately surrounding the plant. CAUTION! Do not allow the bottom of the pot to sit in the water. This can cause root rot, formation of fungus, and other problems. Use something to keep the pot elevated out of the water.
Some pots come with saucers that are designed to hold the pot above the collection of water. If you don’t have these, simply place rocks in the saucer that are large enough to prevent the pot from sitting directly in the water.
A humidifier works great in areas of low humidity. Some installed air conditioning systems have this as an added feature of operation.
As a last resort, try misting the plants with a water bottle sprayer. Works great, just more work. Some commercial greenhouses use misting systems entirely for watering plants.
House Plants and Air Circulation
House Plants need to breathe without being blown away.
Plants need ventilation (air movement) and different amounts for several reasons. Ventilation prevents heat build up, removes harmful gases, and prevent diseases that often occur in closed areas.
Sometimes a home can have “dead spaces” where there is little to no air circulation. The problem can arise from faulty air distribution from the heat/air conditioning system or by the placement of walls that block good air flow. Of course the condition adds to the problem of contaminated air. Correcting the causes of the problem can be costly. There is an alternative.
If you are using plant lights (which build up heat), try to find another location. If not, place a small fan somewhere in the room that will get the air moving in the problem area. Do not direct the fan directly at the plants. The constant swift air from the fan will dry the plants out.
If available, place plants near a window. The differences in temperature created by the window generates some air movement. Usually this is sufficient for plants.
To determine if your plants are getting enough air movement, do the candle test. Light a candle and place it in the effected area. If the candle flickers at all, there is sufficient air circulation.
Are you and your house plants at “odds” over temperature control?
Do what is best for you! The heck with worrying about the house plants. Sound a little selfish? You can be when it comes to temperature control for both you and your house plants. They like what you like when it comes to temperature. Most of our house plants come from tropical climates that usually range in daily temperatures of 65 to 75 degrees F. That is the same range that we usually have our thermostats set at. Voila!
But wait, that is not all. There can still be some problems. Problems similar to air circulation as we discussed earlier.
Sudden changes in temperature, whether too hot or too cold, can send a plant into shock. For example, bringing the plant from a cool environment on the front porch to the inside warm air. It is best to time the moving of the plant when the outdoor temperature and indoor temperature are fairly close.
Plant shock is evidenced most often by wilting or the leaves falling off. In general, the plant gets sick. If not as drastic as just described, the plant may not appear as healthy as before (assuming of course that it was healthy to begin with). Shock can hamper healthy growth.
Shock can occur resulting from plants being exposed to extended periods of time without air conditioning or heating (gone on vacation for example). Arrangements should be made to prevent their exposure to extreme conditions.
One last caution. Avoid drafts. Along with drafts come sudden changes in temperature which can damage plants.
Fertilizing Your House Plants
Before we go any further, lets refresh on some basics of fertilizer. I’m sure you are familiar with the three numbers seen on fertilizer containers like “13-13-13 or 6-12-4”. The order is always the same: the first number represents the percentage of nitrogen (N) present in the mixture; the second number represents the percentage of phosphorus (P) and the third represents the percentage of potassium (K) present in the mixture.
Nitrogen promotes healthy green growth of foliage, phosphorus encourages root growth and flowering, while potassium helps build up reserves for plants that have a dormant period.
Types of Fertilizer
Fertilizer is produced in different forms to accommodate where and how the fertilizer is to be used. For example, a good lawn fertilizer comes in a “pelletized” form for slow release and to prevent “burning” the grass from too much acid at one time that the crushed form of fertilizer gives (the type mixed in the soil for vegetable gardens). However, what is good for the grass is not necessarily good for house plants or other container grown plants.
Why not? Harmful salts are a by-product of fertilizer as it breaks down to provide nutrients to the soil for plants. Outdoors, these salts are leached out (rendered benign) out of the soil via the elements of rain, sunshine, and the soil.
The soil in containers are not able to perform this leaching process as well as the soil outdoors. As a result, harmful salts build up over time doing damage to the plants.
Special fertilizers have been developed for container grown plants to prevent the build up of harmful salts. These fertilizers come in liquid and granule forms. Some brand names include Ozmocote, Peters Special and others.
How and When to Fertilize
The best technique for fertilizing is to follow the directions provided by the manufacturer.
Here is an extra step that I use for container plants that I can handle without too much difficulty. Usually, these are plants like hanging baskets and containers not over a three gallon size. This extra step not only fertilizes the plant, but gives the plant a good watering at the same time.
If I am using a liquid or water-soluble (less expensive) fertilizer, I will mix into the water as recommended by the manufacturer. Using a #3 wash tub (available at most hardware stores) to contain the mixture, the container with the plant is placed in the tub. The plants remain in the water until all bubbling stops then removed.
If I am not using a liquid fertilizer, I will use the same technique with plain tap water to water the plants. When the bubbling stops, the plants will be removed and the granular fertilizer added as recommended. I use this technique about two times during the hot summer months.
Another method is called “constant feed”. A lot of container plants now contain a soilless mixture which requires a lot of attention. An easy way to assure proper feeding is to fertilize each time you water. Use 1/4 of the recommended amount of fertilizer with each watering. Occasionally (about once a month) run clear water over the soil until the water flowing out the bottom appears to be clear. This helps to leach out any build up of fertilizer or harmful salts.
Potting House Plants
How do I know when it is time to re-pot?
Take a good survey of your house plant and determine the following:
The plant begins to wilt within a day or two after a good watering.
The plant has a tendency to tip over.
A build up of a white or yellowish scale forms on the rim of the container and in some cases on the stem of the plant.
Any one of these three conditions is enough reason to re-pot.
Tips for re-potting.
Hold the stem of the plant in one hand and the bottom of the pot in the other. Turn the pot upside down and gently shake. The plant and rootball should slide out of the pot. If not, set the pot back down and run a knife around the inside of the pot between the rootball and the container. Preferably use a knife long enough to touch the bottom of the container. Once again turn the plant upside down and slide it out of the pot.
Now that the rootball is exposed, gently remove about one third of the soil from the rootball. Examine the remaining rootball for any broken or dead roots and remove them.
Some folks may not agree, but there is an extra step that I take at this point. Trim back about one third of the remaining roots. More new roots will form where the root was cut off. As the plant continues to grow in it’s new pot, it will have more roots in which to absorb moisture and food resulting in a healthier growing plant.
Also, I will wet down the rootball prior to placing in it’s new pot. This helps to prevent shock and resulting wilt after the plant has been re-potted. This is a good time to use a liquid fertilizer mixture by soaking the rootball in it prior to placing it in the container. Be sure to use the manufacturer’s recommendations in preparing the liquid fertilizer mixture.
Leave some space between the top of the container and the surface of the rootball. This acts as a reservoir to hold water until the rootbal can absorb it. Not leaving any space will result in the water running off rather than soaking in. It also allows time for the water to wash in soil around the roots, preventing air pockets within the rootball.