Facts, Misunderstandings and Explanations

But there are many sources of bad indoor plantcare information. Much of it starts with a nugget of truth that then becomes exaggerated or taken out of context and applied to situations where it is no longer true. This misinformation then gets passed along by word-of-mouth or on Internet posts and becomes even further distorted. Here are some examples of common misunderstandings:

Fact: A plant will push roots out through pot drainage holes.
Misunderstanding: If any roots are seen coming through a drainage hole, then the plant needs a bigger pot.
Explanation: A plant with lots of room in the pot may have stray roots that grow through the drainage hole. Such a plant does not need a larger pot.

Fact: A plant that is allowed to get too dry will often develop a few or many yellow leaves, depending on the severity of the drought.
Misunderstanding: Yellow leaves are always a sign that a plant needs more water.
Explanation: Yellow leaves are a symptom with many causes. While it is true that lack of water causes leaf yellowing, it is equally true that rotting roots from excess water will also cause leaf yellowing. In addition, temperature extremes, poor soil pH and pest problems can also cause leaves to yellow

Fact: All green plants need light in order to grow and stay healthy.
Misunderstanding: The more light plants get, the healthier they will be.
Explanation: Although many indoor plants do benefit from maximum light, many popular houseplant species cannot tolerate direct sunlight at all. Make sure you know the light requirement for each plant species that you own.

Fact: Direct light refers to natural sunlight that falls directly onto the leaves of a plant.
Misunderstanding: A plant anywhere in a room that receives any natural light through a window gets direct light.
Explanation: Natural light should not be confused with direct light. Natural light is any light whose origin is the sun, as opposed to a light bulb. Direct light is always natural, light, but it is limited to those locations where the rays of sun fall directly onto the leaves of a plant. Direct sunlight is almost always limited to an area within a few feet of an uncovered window.

Fact: All plants use mineral nutrients in the soil surrounding the roots.
Misunderstanding 1: Essential mineral nutrients are used up quickly and must be replaced by fertilizing regularly.
Explanation: Potted plants use mineral nutrients in very minute quantities. Fresh potting mixes typically have enough nutrients to last for several years or more. Adding excess nutrients to the soil can damage the roots and the plant. Plants in low light do not need any fertilizer.

Misunderstanding 2: Some brand name fertilizers are better than others.
Explanation: There is one brand of plant fertilizer that is heavily advertised and sold because of its alleged ability to produce miraculous results. There is no reason to buy fertilizer by brand name. Instead look for a “complete” fertilizer that includes minor and trace elements as well as the macro nutrients (nitrogen phosphorous and potassium). Otherwise buy by price, not brand name.

Misunderstanding 3: Organic fertilizers are superior to manufactured fertilizers.
Explanation: A plant does not know the difference between nutrients that are natural or organic and those that are manufactured. However, a case can be made that using natural products is better for than the environment. So this is more of a personal values issue than a horticultural issue.

Misunderstand 4: Ailing plants should be given plant food.
Explanation: It is extremely rare that a potted plant exhibits symptoms of nutrient deficiency. Discolored and distorted leaves usually reflect a watering or light problem. Online and plant book photos show photos of plants suffering from nutrient deficiencies. Such nutrient deficiencies are rare with potted plants and most often occur because of poor soil or water quality. In particular, the soil pH or acidity may be outside the acceptable range and that renders the nutrients already in the soil unavailable to the plant. In effect, they are “bound up.” The remedy is correcting the soil pH, not adding more nutrients to those that are already unavailable

Fact: Many potted indoor plants benefit from increased humidity.
Misunderstanding: Indoor plants living in dry air that are ailing can be cured by increased humidity.
Explanation: Most all of the popular indoor potted plants are popular because they have proven that they can adapt quite well to low humidity environments. Although there are a few species that require constantly moist air, these plant species are usually used only on terrariums. Plants suffering from “winter doldrums” are more likely to suffer from improper watering and light or from pest problems. Raising the humidity rarely solves these problems.

Fact: Misting a plant with water increases the humidity for that plant temporarily.
Misunderstanding: Misting your plants once or twice per day is an effective way to raise the humidity.
Explanation: Misting raises the humidity for a plant only as long as the water droplets remain visible on the foliage. In a dry, heated environment that is usually not more than 10 minutes. While misting certainly does no harm, increasing the humidity for 10 to 20 minutes out of a 24-hr day does not have much impact on the plants.

Fact: Showers and baths generate more humidity in the bathroom than in other rooms in the house.
Misunderstanding: Plants needing high humidity do well in bathrooms.
Explanation: The humidity that is visible right after a shower dissipates rapidly soon after the shower is turned off and the bathroom door is opened. Unless you are bathing many, many times each day, bathroom plants will not gain significantly from increased humidity. In addition, many bathrooms have no windows or opaque windows that let in less light than the plant requires .

Fact: In nature, plants benefit from dead leaves that rot on the soil above their roots.
Misunderstanding: Leaving dead leaves on the surface of a potted plant will help provide essential nutrients.
Explanation: Outdoors the forces of nature (temperature fluctuations, bacteria, and fungi) work to decompose dead plant material and convert it into nutrients. These natural forces are absent indoors and decomposition does not occur. Dead leaves left on the soil will only attract insects.

Fact: All plants need water to survive.
Misunderstanding: If a plant is not doing well, it must need more water.
Explanation: Certainly a plant that has gotten too dry does need water. However, providing too much water will cause plant roots to rot and over watering is the most common plant care mistake.

Fact: Providing too much water will cause plants to die.
Misunderstanding: You can prevent over watering by adding just a little bit of water each time you water. Never soak your plants.
Explanation: Too much water means watering too frequently. It does not refer to the quantity of water added. When a plant is appropriately dry (this varies from one species to another), then water it thoroughly or until a bit of water runs through the drainage holes. Applying small amounts of water to the surface will cause the lower roots of the plant to die.

Fact: Some plants require acid soil.
Misunderstanding: Adding coffee grounds is good for your houseplants.
Explanation: Very few plants prefer acidic soil. They include Azaleas, Gardenias and a few others. Acidic soil is bad for most other houseplants. Using coffee grounds is not an effective way to control soil pH.

Fact: Low light plants must be protected from direct sunlight.
Misunderstanding: Low light plants do best in dim locations far away from the nearest window.
Explanation: Even low light plants need enough natural light to provide comfortable reading throughout the day. In most cases this is no more than 6 feet away from a sunny window and even closer to a north-facing window..

Fact: Artificial light can be used effectively as a supplement and even as a substitute for natural light.
Misunderstanding 1: Standard incandescent lights are a good source of light for plants.
Explanation: The quality of the light from an incandescent bulb is in the wrong part of the light spectrum to benefit most plants. Fluorescent bulbs provide better quality light for healthy plant growth.

Misunderstanding 2: Special plant grow lights are essential for healthy plant growth.
Explanation: Incandescent plant lights are color-corrected for plants to use, but they are very expensive to operate. Fluorescent plant grow lights are also color corrected or “full-spectrum,” but they are not significantly better for plants than standard warm and cool white fluorescent bulbs. Standard fluorescent lights are energy efficient and less costly than special fluorescent grow lights.

Fact: It is not easy to tell how moist the soil is in the lower regions of a pot.
Misunderstanding: A moisture meter will probe deep into the soil and reveal exactly how moist the soil is.
Explanation: Moisture meters are notoriously inaccurate because they measure soil conductivity, not actual soil moisture content. Understanding that soil dries out from the top down will allow you to “read” the lower moisture content by feeling the top 1 -2 inches of soil with your finger. If you really want to know how much moisture there is deep in the pot then use a soil probe (www.soilsleuth.com) or a wood dowel.

Fact: Plant pests can be treated successfully without using pesticides.
Misunderstanding: Home pesticide remedies don’t work because the pests keep coming back.
Explanation: Most any home remedy can be effective in eradicating plant pests. However, for any remedy to work, you must get 100% complete coverage of the entire plant. Home remedies usually include water, soap and oil and work only when they are in direct physical contact with each critter. If you miss just a couple of these tiny creatures, they will reproduce and come back to haunt you down the road. Thoroughness of coverage matters more than the product that you apply.

Fact: Plant pests can spread from one plant to another.
Misunderstanding: An ailing or pest-infested plant must be quarantined.
Explanation: Insect pests will transfer to nearby plants or may be carried on your person or clothing to other plants farther away. However, once a plant has been treated thoroughly for those pests, it no longer needs to be quarantined. You do need to monitor your infested plants carefully, but there is no reason to quarantine them for a long time.

Fact: Plant diseases can be transmitted to other plants if tools and hands are not sterilized.
Misunderstanding: It is essential to sterilize all cutting tools immediately after using them on any plant.
Explanation: Disease transmission is a big problem for nursery growers whose livelihood depends on huge crops of plants grown closely together. The spread of an infectious disease can wipe them out. Most bacterial and fungal diseases occur and spread in greenhouse environments, not in the home or office. That is not to say that it never occurs in our homes and offices, but obsessively sterilizing your tools after every use is probably unnecessary. If you have a particularly valuable or treasured plant, you might want to make sure you use only clean tools when pruning or trimming.

Fact: All plants need nutrient-rich soil to grow well.
Misunderstanding: Nutrient-rich compost and organic soil are environmentally sound and superior to packaged potting soils.
Explanation: While garden soil and compost are often rich in nutrients, they also are unsterile and may be a source of unwanted pests and diseases. Outdoors, naturally occurring plant pests and pathogens have natural checks on their spread, but indoors they can run rampant. To keep your home free of insects and plant diseases, it is best to use peat-based, soilless potting mixes that are sterile.

Fact: Excess chlorine and fluoride can damage a plant.
Misunderstanding: Most municipal water supplies have small amounts of chlorine and fluoride added so it is best to let tap water stand overnight in an open container before using it.
Explanation: Both chlorine and fluoride can cause damage to certain plant species. However, the levels of concentration of both these substances in water supplies are so low that they are unlikely to damage even the most sensitive of plants. Heavily chlorinated swimming pool water, however, is concentrated enough to cause plant damage. Although some chlorine does dissipate into the air from an open container, it is unclear if enough dissipates over night to make a difference. Fluoride does not dissipate, it concentrates as the water stands and evaporates. Other than pool water, neither chlorine nor fluoride additives to tap water should be a problem for your plants. Letting water stand in open containers offers no benefits.

Fact: Hard water can damage plants.
Misunderstanding: Using a water softening agent or letting tap water stand overnight will eliminate the hard water problem.
Explanations: Hard water is water with a high concentration of minerals or salts. Over time they can build up to toxic levels and damage plant roots. Water softeners make the water easier to use, but they also add even more mineral salts to the water, so do not use softened water for your plants. Letting hard water stand overnight will only concentrate the minerals even more as some of the water evaporates while the minerals stay behind. If you have hard water, use filtered, distilled or rainwater instead.

Fact: The first leaf that emerges at the base of a Corn Plant flower stem is often stunted or distorted.
Misunderstanding: Allowing a Corn Plant to flower will cause all future growth to be distorted.
Explanation: Any leaf distortion following flowering is usually limited to only one or two leaves that can easily be removed.

Grandma Was Wrong
I know that picking a fight with anyone’s favorite elderly relative – particularly one who had a green thumb – is not a good idea. But this is not personal. It is really my way to grab your attention so I can explain some out-dated plant care practices that are no longer practiced by plant professionals.
• Adding drainage material to the bottom of the pot
• Using dirt from the backyard or garden
• Watering with ice cubes
• Adding coffee grounds, egg shells, tea leaves and Epsom salts to the soil
• Using dead leaves as mulch
• Letting water stand overnight

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