Most houseplants are hybrids of plant species which grow wild, somewhere in the world. A good rule of thumb for keeping them healthy is to try to match the same environment from which they originated. You may not be able to match every criteria for your plant, but every small step you take to ensure the plants comfort will be a giant step towards keeping your friend healthy.

Proper lighting and watering are, by far, the most important criteria for the health of your house plant, but temperatures and humidity will drastically affect your plants as well. Generally, tropical plants enjoy a relative humidity of 50%-70% and warm temperatures. Unfortunately, when temperatures in the home rise above 67 degrees F., the humidity drops drastically, so it may be necessary to sacrifice a few degrees of warmth in lieu of an increase in the humidity

Of course, there are always exceptions to the rule. Succulents being the most notable, which prefer warmer and drier conditions. At temperatures below 60 degrees, African violets will stop blooming, Poinsettias may drop their leaves, and the leaves of Gardenias may turn yellow. It will be a great benefit to your plant if you do a little research about what the needs of your particular species happen to be.

I recommend reading "House plant problems" for a few more tips about keeping your house plants happy and healthy!

While many problems are related to insects and disease, most seem to be of an environmental nature, especially in the winter. House plants are all hybrids or species plants which grow wild somewhere in the world. Try to match the environment from where the plant originated from for the best success. You may not be able to match every criteria for the plant, but every step you take towards the plants comfort will be a giant step towards keeping your friend healthy.

Temperature, humidity and light
Houseplants, even though they may be of a tropical nature would rather sacrifice a few degrees of temperature in the home than the moisture in the air which they need to survive. Even though the plant may prefer a warmer situation, it comes down to the lesser of two evils, cool temps or low humidity. Heated rooms tend to be dry rooms, especially if they are heated with forced air, or fire. Even rooms that have steam or hot water radiant heat will be somewhat dryer. If you want your plants to succeed, keep your temperatures as low as possible, while still remaining comfortable yourself (never below 50 degrees). Once the temperature goes above 67 degrees F., the humidity in the air begins to drop dramatically. Keep in mind that because glass is a poor insulator, the temperature near windows will be considerably colder. At night, be sure to close the drapes or move the plant to a warmer part of the room.
There are exceptions to the rule. Succulents being the most notable, which prefer warmer and drier conditions. At temperatures below 60 degrees, African violets will stop blooming, Poinsettias may drop their leaves, and the leaves of Gardenias may turn yellow.

Leaf loss or yellowing is often caused by lack of humidity. The majority of houseplants do best with a relative humidity of between 50 and 70 per cent. Plants create a certain amount of humidity themselves through transpiration through their leaves, from the soil, and even the pots if they are porous. The more plants you have in a room, the higher the humidity will be, and if the closer the plants are together, the more they will be able to benefit each other. Setting the pots onto a bed of small pebbles and gravel in a shallow tray will allow you to add water to the tray, raising the humidity without giving the plants 'wet feet'. Except for fuzzy leaved ones, houseplants enjoy a daily misting with room temperature water. Placing water filled vessels around the room will also add to the moisture in the room.

Just as you and I do, plants need to breathe, and enjoy a little fresh air. It isn't necessary to have constantly changing air, but lightly moving air can often make a difference in the plants growth and health. A few plants may suffer when they grow in the presence of natural or coal gasses. The effects of gas heat may range from failure to bloom to a complete loss of leaves. Others may just appear to look unhealthy for no apparent reason.
Do you talk to your plants? No.... I don't believe that they understand you, but plants breathe CO2 which we exhale, and in turn they exhale oxygen which we need. I've heard of oxygen bars where you PAY to breathe canned oxygen. Seems to me to be more prudent to have a chat with your Philodendron, and give each other a boost.

I suppose that the most important elements needed for plant health are water and light. Most plants have dormant and active cycles. Watering, just as feeding your plant differs greatly from season to season. Plants sense the natural shortening of daylight hours and may go dormant as they would in their natural habitat. This is usually a time when the amount of watering is decreased. On the other hand, many plants actively begin to grow or bloom, so they must have more water, and be fed. While plants are dormant they should only a minimum amount of water each time that the soil becomes dry to the touch an inch below the surface. During periods of active growth the plant should be thoroughly soaked as soon as the soil dries. There are no hard and fast rules to watering, because every situation is different, according to temperatures, and soil types etc. It is better to keep a plant on a slightly dry side than overwatered. More houseplants die from overwatering than any other cause. City water is treated with chemicals for your safety, however plants don't like chlorine or fluoride, so it's a very good idea to allow the water to sit in an open container for 24 hours prior to using it on your plants. This is enough time for the chemicals to dissipate and evaporate from the water. Even though my water comes from a spring, I still keep a couple of gallon milk bottles filled for watering so that it is at room temperature when I use it.

The amount and the intensity of the light that the plant receives dictates much of a plant's life cycle. Even though the plant maybe from the jungles where it lives in the shade of trees, appears to be getting plenty of light, the intensity of the light indoors is going to be much lower. Insufficient light usually manifests itself with pale foliage, lanky growth, and general lack of luster. When this happens you must do whatever you can to increase the light intensity for that plant. This is usually rectified by moving the plant closer to the window, or moving it to another room with different light exposure. When you change the light for a plant, do it gradually to accustomize to the brighter light. Plants will sunburn if they are put into too bright of a light after their skins have 'tenderized' from lack of light. Plants should never be placed between a curtain and the window if the nights are cold, even if they are sun lovers. It is better to have a sheer curtain which will admit the light, and have the plant in the heated area.
It isn't necessary for your plant to even know that it is winter. You can dictate many of your plants functions by giving them supplemental artificial light. There are 'grow lights' on the market today that successfully imitate natural sun. These lights aren't perfect, and if they are the sole source of lighting, it is necessary to have them on for 12-16 hours each day. It is best to have the set on a timer so that the light hours are regular for the best results. If your intent is just to fool your plant into thinking that it is a certain season for blooming or whatever reason, you can set the timer to come on as the light begins to fade, and make your plants day as long as you'd like. Many flowering plants and foliage plants actually do better indoors when grown under artificial lights. Keep in mind that plants like to rest now and then too, so if you are using the lights, cut back the hours now and then and let your plants have a temporary period of dormancy.

Problems and possible causes

• Leaf edges brown and dried ...Too much heat, lack of humidity.
  
• Rapid defoliation ...Rapid changes in temperature, or light (plant taken from bright light to relatively low light), possible overwatering, underwatering, or exposure to drafts.
  
• Failure of blooming plants to flower ...Insufficient water or light, over fertilizing.
  
• Flower buds drop before opening ...Temperature fluctuations, drafts, lack of humidity.
  
• Silver or red blotches on foliage ...Too much direct sun.
  
• Gradual defoliation (lower leaves yellow and fall) ... Overwatering (root damage), underwatering (not enough water to support full foliage), lack of sufficient light, or lack of fertilizer.
  
• New Growth Wilted, or burned ...Too much fertilizer (leaching needed), cold drafts, hot drafts, to dry, sunburn, too warm, or freeze damage.
  
• Entire plant wilted ...Too little water, too much water (roots rotted), too much fertilizer, or exposed to cold temperatures.
  
• Spotted foliage ...Overwatering (check roots), burn from direct sun, cold water on foliage, fungal infection (especially if plants are in very humid, wet conditions), or pollutants in the air (fumes from gases, etc.).
  
• Foliage is pale and weak looking ...Insufficient light conditions, too dry (soil or air), or lack of fertilizer.
  
• Browning of leaf tips or leaf margins ...Lack of humidity, fertilizer burn, poor water quality (chlorine, fluoride, sodium, boron, soluble salts, etc.), incorrect fertilizer, spray damage (insecticides, oil, leaf-glossing materials), incorrect soil pH or pollutants in the air (gasses etc.).
  
• Stunted plants ...Excess fertilizer (root damage), lack of water,> or overwatered (root damage).
  
• New foliage is small, pale, and spindly ...Lack of light, lack of fertilizer, or soil too dry.
  
• Leaves yellowed between veins (veins remain green) ... pH either too high or too low, iron deficiency (high pH), or magnesium deficiency (when pH is too low or acidic).
  
• Leaves drop continuously, new leaves on tip are small and curled ...Unburned gasses in the air, spray or vapor damage from cleaning fluids, industrial pollution, or general pollutants in the atmosphere, possibly aphid or mite damage.
  
• Tiny white spots on leaves ...Primarily spider mites. ,
  
• Cottony masses on stems, round or oval shaped bumps ...Mealy bugs
  
• Sticky spots on foliage ...Primarily aphids
  
• Small brown bumps on stems or foliage ...Scale insects
  
• Fuzzy, grey mould that covers flowers, leaves and stems ...Botrytis blight - fungal disease generally caused by dead leaves and spent flowers being left on the plant, too much humidity or poor ventilation.
  
• General drooping of the entire plant ...Crown, stem or root rot - caused by overwatering, especially during the winter months when plants are dormant and do not need much moisture.
  
• Brown or yellow leaf spots ...Fungi which usually develops when water is allowed to remain on the leaves. Cold water can also be a cause of spotting. Use room temperature water for misting and watering, and make sure the foliage dries before night.
  
• Mildew ...Powdery mildew is an airborne fungal disease. African violets and Begonias are particularly succeptible.

Good cultural practices will eliminate many diseases and other houseplant problems. If insects and fungal diseases are a problem, visit a reputable nursery to find an appropriate chemical to combat the problem, and ALWAYS read and follow the manufacturers recommendations for that product. Many problems may be halted by removing damaged parts of the plant if they are detected early enough. However vigilance is necessary afterward to make sure that you have completely eliminated the problem. I will be dealing with insect and disease problems in depth, in the near future.

Plants Specific Need