Container Gardening

Next to regular watering, the most important part of container gardening is fertilizing.  In the ground, plants can pull nutrients from the dirt, slowly and steadily.  A container, on the other hand, is a closed system: nothing goes in but what you put in.  This means that if you want healthy vegetable plants, you have to supply the fertilizer to keep them healthy.

So, what is fertilizer?  Fertilizer is a combination of basic nutrients and minerals which plants need to survive.  Fertilizing your plants regularly works like vitamin pills do for people: they provide balance to a diet that is almost certainly inadequate to start.

There are three main nutrients that plants need: nitrogen, phosphorus, and potassium.  A complete fertilizer will contain all three of these nutrients.  A balanced formula contains all three in equal amounts.  Depending on what you are growing, you will want different proportions of these nutrients.

Nitrogen is used by plants to build healthy foliage.  It is critical for all vegetables, but especially important in vegetable container gardens where you are focusing on leafy vegetables.  Lettuces, spinach, etc, would want a fertilizer that focuses on nitrogen.

Phosphorus is used by plants to produce healthy flowers and fruits.  Tomatoes, peppers, squash, and the like will need more phosphorus, especially when they are ready to shift from growing leaves to growing fruit.  When growing tomatoes, it can be useful to add a phosphorus booster at this stage to assist them in moving to fruiting.

Potassium helps build healthy roots in all plants.  Generally, the healthier the roots, the healthier the plant, so keeping the potassium level where it should be can prevent many plant problems.

Every commercial formula will tell you, somewhere on the packaging, what the proportion of the nutrients is to each other.  It is the proportion that matters in fertilizer, not the absolute amount: you will need to dilute fertilizer to use it.

To tell the proportion of these nutrients in a commercial fertilizer, look for a series of three numbers on the label.  This is the N-P-K number, viewed in the form 10-20-10.  The numbers represent the percentage of the fertilizer that is, respectively, nitrogen, phosphorus, and potassium.  The numbers are always written in that order.

In addition to the three major nutrients, your plants need a collection of lesser nutrients.  These include calcium, magnesium, sulfur, iron, manganese, copper, chlorine, boron, zinc, and molybdenum.  A good all-around commercial fertilizer will contain all of these in trace amounts.  If you ever find your plant struggling, and cannot tell why, applying a mix of these trace elements to your plants may help them revive.

I generally start my planting with a potting mix that comes pre-fertilized.  This means the mix has a fertilizer mixed in which is released slowly by watering.  Over the course of a few months, the plants will unlock and consume that fertilizer.  On top of that fertilizer, it’s a good idea to fertilize every week or two weeks according to the instructions on your fertilizer.

Be careful not to over-fertilize!  Many of the substances found in a standard fertilizer, including the main nutrients, can actually damage plants if overused.  Keep to the standard schedule unless your plants seem to be struggling.

Tags: Fertilizer

This entry was posted on Wednesday, June 10th, 2009 at 6:00 am and is filed under Fertilizer. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.