MIDDLETOWN - Recently I had a conversation with a friend who was complaining--she seemed to be able to garden, but she wasn’t able to grow indoor tropical plants.

       I went through the list of do’s and don’ts for the particular plants she was trying to grow but nothing seemed to click. The final question was the fertilizer. â€�"Is it high in nitrogen?” I asked. She wasn’t quite sure, then she asked me why.

       One of the biggest follies I hear about when it comes to growing plants is the lack of fertilizer knowledge. I know I have written about this before, but I think it bears repeating. When fertilizer is bought it is very important to read the side of the package and know what it contains.

       There are three numbers listed on all fertilizers. The first number is nitrogen. Nitrogen is good for big green plants. Look at a bag of lawn fertilizer and its first number is generally in the 20-30 range. This is because people that use it want a nice green lawn. This really isn’t good for indoor plants. The nitrogen for indoor plants, or really any plant, should be on the low side, between 5 and10. One of the other problems with a high nitrogen content is that it eventually will burn out the roots. It is difficult for indoor plants’ soil to get flushed out, so the fertilizers will start to build up in the soil.

       The second number is phosphate. This gives the plants a strong root system and helps them flower. If, this number is lower than the nitrogen number, chances are the plant will not flower and it will be big and green. Going back to the grass fertilizer, its second number is generally from 0-2, unless it’s a starter fertilizer, which has a higher number. The starter fertilizers are trying to get a good root system going to establish the lawn.

       The third number is potash or potassium. This is important to keep plants healthy. It promotes good cell growth and aids in fighting diseases.

       Another fertilizing mistake is adding too much. More is not better, especially with indoor plants. Following the directions is very important. Too much will hurt the plant and eventually kill it. There is also the chance of build-up within the plant soil. Unlike outdoor plants where the fertilizers are leeched away, the indoor plants don’t get the kind of watering to flush the soil out. Ever have clay pots and get a white substance on the outsides? Those are the salts and minerals from the water accumulating on the porous clay. This is one reason I put most of my house plants out for the summer. The plants can get a good flushing with a thorough watering.

       I should also mention I don’t advocate fertilizing lawns. The high nitrogen fertilizers are what are causing one of our biggest pollution problems in the Long Island Sound--algae. When it rains, those fertilizers get washed down the storm drains and into our river systems, which eventually go into the sound.