One mistake gardeners commonly make is that they overfertilize their plants, which can damage their roots and lead to poor fruiting, poor flavor, and excessive vine growth. In fact, some horticulturists say many more problems are related to overfertilization than to underfertilization.
Fertilizers, which provide nitrogen (N), phosphorus (P), and potassium (K), are a good way to give your plants the nutrients they need. (The three numbers prominently featured in this order.) However, you should have a sample of your soil tested by your local Cooperative Extension office (listed in the telephone directory under U.S. Government, Department of Agriculture, or by searching the Internet for Cooperative Extension Service and your state’s name) if you know nothing about its fertility, so that you can better judge what type of fertilizer the soil needs.
Keep in mind that more fertilizer isn’t better. In general, you should apply less than the bag indicates; certainly don’t apply more than indicated. Most packages recommend using a strong dose so you’ll purchase more product. Don’t go above the package’s recommendation unless you know your specific soil needs it.