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Fertilizer 101

5 min read | Dec 13, 2012 | Resources 

Walk into the fertilizer section of any nursery or garden center and you will be overwhelmed by the choices available. There are bags and bottles and boxes, all claiming to be the perfect solution for your under-performing plants. There are specialty products, formulated for roses, orchids, acid-loving plants, vegetables, and bulbs. There are natural and synthetic fertilizers. There are fertilizer blends and ones which contain only a single nutrient, such as nitrogen. There are pellets, liquids, and granules. All the fertilizer containers have a bunch of numbers, like 10-6-4 or 5-5-5, and lots of chemical symbols and percentages. How can we sift through all this information to choose the best fertilizer for our garden? Understanding a few basic principles about how fertilizers work and how they are marketed will help you sort through the fertilizer shelves.

All fertilizers are labeled with three numbers that represent the primary nutrients that plants need: nitrogen, phosphorous and potassium. They are always listed as a percentage of those nutrients and always in that order. For example, a 4-1-2 fertilizer contains 4 percent, by weight, nitrogen, 1 percent phosphorous and 2 percent potassium. These can occur in different ratios and combinations, but they all represent the strength or concentration of the fertilizer. So an 8-2-4 would be twice as concentrated as a 4-1-2. This is important when comparing prices because it would take twice as much of the second fertilizer to equal the same amount of nutrient as the first.

What do the Three Primary Nutrients do? – Nitrogen is very important in plants for good foliage growth and dark green color. Phosphorous is important for rooting and also for blooming, and potassium is important for cold hardiness and plays a role in fruiting and blooming. It is possible to use a balanced fertilizer, one where the three numbers are equal or close to one another like10-10-10, throughout the growing cycle.
For vegetables grown mostly for their leaves like lettuce or other greens, a fertilizer with more nitrogen than anything else (a higher first number) is best. For vegetables that flower first like peppers and tomatoes, a fertilizer with a higher proportion of phosphorus (a higher middle number) works well. Some gardeners produce great results by using a high growth (high nitrogen) formula for the beginning of the growth cycle and then switch to a high bloom (high phosphorus) fertilizer when the plants begin to flower. Espoma Garden-Tone, Garden Food and Tomato-Tone are excellent choices for all your veggies.

There is a difference between the fertilizer needs of annuals and perennials. Annuals complete their life cycle in one growing season, so they need more fertilizer than perennials that have the advantage of starting over each season from a hardy root system. Annuals could live with the same amount of fertilizer as perennials or any other plants, but to get the most out of them, it pays to provide annuals with fertilizer throughout the season. Most annuals are grown for their prolific flowering but there are some varieties grown for their beautiful foliage. Annuals that are grown for their flowers need lots of phosphorous to encourage blooms. That’s the middle number. Annuals grown for their foliage need more nitrogen. Nitrogen is the first number and it encourages lots of leaf growth. Since most perennials only bloom for a short period each season, it is even more important that they have healthy, attractive foliage. Water-soluble fertilizer such as Miracle Gro or Schultz’s Bloom Plus are good for annuals. Be sure to apply water-soluble fertilizer to annuals about every two weeks throughout the growing season. Water-soluble fertilizers can be used as an occasional quick snack for perennials, but should not be the primary fertilizer. Perennials prefer a dry fertilizer that is slow released such as Osmocote, Plant-Tone or Flower-Tone.

When fertilizing trees and shrubs, keep two things in mind: (1) Fertilizer is beneficial only when it is needed; and (2) Use it in the right amount, at the right time and in the right place. Time your application to coincide with active root growth. Acid-loving plants like evergreens, azaleas, camellias, dogwoods and rhododendron should be fertilized in early spring and again in the fall. Use half the recommended rate for the fall application. We recommend Espoma Holly-Tone. Shade, fruit, and ornamental trees should also be fertilized twice each year; in early spring before growth starts and again in the fall after leaves drop but before the ground freezes. We recommend Espoma Tree-Tone for these. Avoid fertilizing trees and shrubs during the summer months. Roses are a little different. They like to be fertilized once a month during the growing season with a rose food like Espoma Rose-Tone.

Providing the correct amount and type of fertilizer promotes healthy flower production and foliage growth while applying too much can cause other problems. Many gardeners have the false impression that the more you fertilize your plants, the more they will grow. Always READ THE LABEL before you apply any type of fertilizer. Application times, amounts and conditions must be followed to the letter. In other words, only apply as directed on the package. Most fertilizers should not be applied to dry soils. Doing so can burn the surface feeder roots. All of the dry-type fertilizers should be watered-in thoroughly, immediately after application.

I hope this article was informative and helpful. If you have any questions, feel free to give us a call or better yet stop by. We’d love to see you.

Cindy K.