Question
hi,
i was wondering these questions:

How often should I fertilize my house plants?

types of Fertilizers

history of fertilizers

P.s links(websites)are ok to!

Answer
A poet at heart, I see.

Houseplants do not need to be fertilized often.  Fertilizer companies would like you to use their stuff as much as possible.  But in reality, you don't need to do that.  And chemical fertilizers build up in houseplant soil.  Use too much, and you'll do more harm than good -- burning the roots with the chemicals is NOT a pretty sight.

The basic rule you can go by is that when a plant is in 'active' growth (mostly in the Summer), you can fertilize it once or twice for the season.  Spring, then Summer, once only each time.  That's basically 2x a year.

A flowering plant that will soon be in bud would benefit from a fertilizer that has a higher MIDDLE number in the N-P-K analysis.  So if it says 2-10-2, you are on the right rack.  If it says 10-10-10 you are looking at BALANCED fertilizer, not great for flowers but excellent for non-flowering plants.  All fertilizer by law has to have these numbers somewhere on the container.  Just find it and you'll know what you're buying.  Never go by the picture on the box.  Those pictures are designed to sell the stuff.  They tell you NOTHING about the contents.

The history of fertilizers -- that's a tall order.  fertilizers seemed utterly amazing when they were first invented by a chemistry teacher named Justus von Liebig, the 'Father of the Fertilizer Industry' for cooking up the world's first chemical Nitrogen Fertilizer.

Nitrogen is needed to make Chlorophyll and Leaves.  It is the first Macronutrient.

Phosphorus is the second Macronutrient.  It is needed for flowers and roots, among other things.

Potash is the third Macronutrient.  Plants that get enough Potash (aka Potassium) are tougher during Winter; have stronger roots; grow more vigorously; and produce bigger, better fruits and vegetables.

Macronutrients are the primary nutrients needed by Green Plants.  Micronutrients are essential, too.  But it's the Macros that make the Fertilizer business.  Micros are almost always available in the Soil, and plenty of them.  You can read all about the inventor here:

http://www.woodrow.org/teachers/chemistry/institutes/1992/Liebig.html

Barbara Bromley, Master Gardener serving the Rutgers University Mercer County Cooperative Extension in the Garden State, posts some of the clearest, most informative guides to gardening and pest management that I have ever come across.  Here's her cheat sheet on Fertilizers, which will make you an instant authority on EVERYTHING you need to know about NPK and more:

http://www.mgofmc.org/fertilizers.html

For those days when you are just aching to know what if anything is wrong with your Tropical Hibiscus, here's a great website on nutrient deficiencies, complete with illustrations, called 'Symptoms of Deficiency In Essential Minerals', by former UCLA professor Wade Berry:

http://4e.plantphys.net/article.php?ch=5&id=289

For sheer pleasure of their company, Dirt Doctor Howard Garrett and Georgia Gardener Walter Reeves share their gardening wisdom with people everywhere:

http://search.yahoo.com/search;_ylt=A0geu9Df4x5H4yUBlxdXNyoA?p=dirt+doctor&fr=my...

and

http://www.walterreeves.com/tv_radio.phtml

One of my favorite authorities is an Iconoclast Ne Plus Ultra who pulls no punches when it comes to baloney.  You have to read her 'Myths' list to really appreciate her direct advice and common sense.  This is a woman who WRITES the rules, Master Gardener Linda Chalker-Scott, PhD, at the Washington State University Extension Center:

http://www.puyallup.wsu.edu/~Linda%20Chalker-Scott/Horticultural%20Myths_files/M...

One of Dr Scott's recent essays addresses the Myth 'Adding Epsom Salts to gardens is a safe, natural way to increase plant growth'.  Dr Scott looks at a half dozen claims and picks them apart one by one.

Finally, for SHEER BALONEY, I refer you to England's Crop Protection Association 'Common Sense Gardening' website, which explains that (LOL) because large quantities of table salt can kill you, it is OK to spray DDT around the house:

http://www.garden-care.org.uk/myths.asp

The way they see it, we're MADE of Chemicals, so let's use as many as possible, right?  Ann Coulter preaches to the same people.  Members of the Crop Protection Assn are listed on its website.  The list includes Pesticides and Herbicides Companies that make money on chemicals (surprise surprise): Dow, Bayer CropScience, DuPont UK, Fine Agrochemicals, Monsanto...

Thanks for writing.