First things first: commercial fertilizers are labeled with 3 numbers that refer to 3 essential nutrients plants need to thrive. The first number indicates Nitrogen (N), the second Phosphorus (P), and the third Potassium (K). Nitrogen promotes green, leafy growth. Phosphorus supports the root structure, flower blooms, and fruit production. Potassium helps plants develop strong, resilient cells that improve the plant’s overall hardiness. A fertilizer labeled 10-10-10 is a good all-purpose choice, but if you are growing plants that bear fruit or flowers, a fertilizer with a higher middle number is a better choice.
More is not necessarily better when it comes to fertilizer. Just because a plant has yellow leaves or looks unhealthy, does not mean it needs fertilizer. This could be due to the planting site or the cultural conditions. For example, yellow leaves on a Gardenia could be a symptom of soil that is too alkaline, too compacted or too wet. Check this first before applying fertilizer. Too much fertilizer can kill your plants; what a waste of time and money!
Here are some quick guidelines for what to apply, and when:
Shrubs, Perennials, and Trees—try a slow-release fertilizer applied in the early Spring (March-April)
- Annuals, Vegetables, Roses and Other Heavy Bloomers—these do well with liquid or granular fertilizers applied according to package directions, usually every 3-4 weeks. Some vegetables are “heavy feeders,” and will thrive with even more frequent applications.
- Warm-Season Grasses—fertilize when your lawn starts to turn green in the Spring.
- Cool-Season Grasses—fertilize in the Fall.
As we said, if in doubt, you can use garden-variety 10-10-10 fertilizer for most plants, trees and shrubs. However, if you’re feeding azaleas, camellias and rhododendron, purchase a special blend for these plants that includes a higher acidity. These plants like soil that is more acidic than most soils in North Georgia tend to be.
If you’re not sure about the composition of your soil, do a soil test. Kits are available from the University of Georgia Extension Office at Exit 24 off I-985 (770-535-8293) The kits are free; the test is $8 and will tell you how best to amend your soil for the particular plants you’re growing.