How to Choose the Right Fertilizer for Lawns and Plants

The brands of fertilizer available are often overwhelming. Information about what works best is often flawed. Knowledge yields the best results.

Centipede is a popular grass especially in the southeastern U.S. It is low-maintenance, reasonably shade-tolerant, and makes a lush, attractive lawn when given proper care. When it comes to fertilizing many people tend to overdo it. Centipede is a typical lawn grass and needs little phosphorous as is the case for many lawn grasses.

Learn what the Numbers and Chemicals on the Label Mean

Searching for fertilizer may seem like a daunting task with all of the information on the bag. What’s more, different manufacturers often seem to recommend different formulations for the same grass or plant.

Fertilizers always have information about what’s in the bag or box. The main ingredients for all fertilizers are compounds containing — in order — nitrogen, phosphorus, and potassium.

For example, if the formulation numbers are 18-6-12 that means that the contents contain, by weight, 18% nitrogen, 6% phosphorus, and 12% potassium.

Other trace compounds may be present depending on the plant, but the three prominent numbers represent nitrogen, phosphorus, and potassium — they are of primary importance.

Good Fertilizers Should Be Formulated to Fit Particular Plant Needs

Typically, all plants need nitrogen, phosphorus, and potassium, but not in the same proportions. More is not necessarily better and can be deadly depending on the plant.

Lawn grasses generally need a healthy dose of nitrogen to create the green blades. Nitrogen is an essential ingredient in chlorophyll, which makes plants green. Chlorophyll helps plants make food and grow.

Phosphorus is needed for flowers and seeds and strong roots and stems. It helps plants maintain general overall health and energy. Grasses tend to need more phosphorus when new and in the process of developing roots and stems.

Plants that are generally referred to as “flowers,” like petunias and marigolds often benefit from a fertilizer with 50% or more phosphorous to produce lots of blooms. Indoor flowering plants do well on 20-20-20 or less.

Next to nitrogen, plants typically need potassium. It also aids in photosynthesis, but plays a role in disease resistance. Potassium assists in the manufacture of proteins for growth and cell functions.

Before fertilizing anything it is good to know specific plant requirements. Too much nitrogen on tomatoes, for example, may result in lush green plants with great leaves, but the fruit may be a disappointment in size and number. House plants typically need much less fertilizer than outdoor plants.

Get the Right Fertilizer for Specific Grasses

Different grasses require different formulations. Centipede does well on a single spring fertilizing of 18-0-6 in well-established lawns. New lawns or poor soil may require 18-4-18 with another light fertilizing near summer’s end.

Bermuda grass thrives on high nitrogen fertilizers — 28% to 31% ­— about every month or so during the summer with an increase in potassium at the end of the growing season.

There are too many types of lawn grass to list here, but state or regional agricultural stations can provide information. They can also perform soil tests that give precise needs of different lawns.

The application of fertilizer requires a good quality spreader that can be adjusted for accurate spreading. Broadcasting by hand is risky and presents the risk of over-fertilizing some spots and killing the grass.

Fruits, Vegetables, Shrubs, and Houseplants Need Different Fertilizers

Green, leafy vegetables require more nitrogen than fruits. A 15-15-15 mix is suitable for a wide range of leafy vegetables, while fruit plants prefer 6-24-24 or 6-12-18. A soil test is always a good idea.

Be careful not to fertilize vegetables with fertilizers containing weed killing chemicals, as they are likely to kill the plants. The same holds true for ornamental shrubs, which generally thrive on an “all purpose” 10-10-10.

Houseplants like liquid feedings when watered according to directions. Some house plants need more attention than all purpose formulas ­ — particularly orchids, violets, and most houseplants during the winter when growth slows.

Factors to Consider when Fertilizing

There are other considerations to keep in mind when selecting a fertilizer. It’s not all about numbers.

The percentages are never exact, so don’t worry about getting a precise formulation. A little more or less of the three main nutrients is not likely to present a problem.

The condition of the soil — especially pH — will affect the absorption of the fertilizer. A soil test can provide this information.

There are other minerals that can make a big difference for particular plants that might have to be purchased separately.

Too much or too little moisture can affect the available nutrients in the soil. Keep up with the amount of water.

Fertilizing lawns and plants can be confusing. Remember your three essential nutrients. Don’t throw just anything on any plant. Some plants have low fertilization needs; others demand regular and frequent feeding.

Don’t assume that unhealthy plants or lawns are starving — they may have a disease or fungus. Selecting fertilizer is the easy part of plant care. Invest a few dollars in a good book and use Internet sites maintained by government agricultural agencies.

Sources:

A Gardener’s Guide to Fertilizing Trees and Shrubs

Fertilizer Recommendations for Landscape Plants