Gardeners using rich, organic soil may need little, if any, additional fertilizer. (Justin Sullivan / Getty Images)
When choosing and using fertilizers, it's important to remember that although horticulturalists often refer to fertilizing as "feeding" a plant, in reality plants manufacture their own food via photosynthesis. So a plant receiving the required amount of sun and water will grow, but the right nutrients -- provided in the proper amount -- will optimize their health along with increased production and improved quality of the harvest.
Although some gardeners prefer to add fertilizer to the soil when preparing the planting bed, others feed individual varieties according to their specific needs.
Leafy vegetables, such as lettuces and chard, do best in organic rich soil and a one-time top dressing of nitrogen fertilizer such as blood meal, cottonseed meal or liquid fish emulsion.
Top dressing means sprinkling the fertilizer on the surface of the soil. If the soil is mulched, move the material aside, sprinkle the fertilizer on the soil and replace the mulch. When using organic fertilizers, covering the granules with a couple of inches of soil or compost will hold it in place and hasten its breakdown.
Over-fertilizing tomatoes by giving them too much nitrogen will produce lots of leaves and little fruit. Like a lot of tomato mavens, I charge my garden soil with organics and then side dress with a fertilizer that is rich in phosphorous a couple of times during the growing season.
I fertilize my tomato seedlings weekly with liquid fish emulsion at half the recommended rate, putting off using fertilizer at planting time. When the plants begin to set fruit, I side dress. For large varieties such as beefsteaks, that's when the fruit reaches the size of a golf ball; for cherry tomatoes, the size of a pea. To side dress, deposit the recommended amount of fertilizer in a circle about four to six inches from the stem of the plant.
When choosing a granular fertilizer for vegetables, I look for a slow-release organic type, such as Espoma Garden Tone. Espoma Tomato Tone, developed specifically for use on tomatoes, includes calcium in the mix to help prevent blossom end rot. The Espoma fertilizers are enhanced with Bio-Tone beneficial organisms that improve soil health while "feeding" the plant. For more information check out their Web site, http://www.espoma.com">www.espoma.com.
Keep in mind when you purchase a fertilizer, the higher the numbers, the stronger the content, so read the label and follow the recommendations to prevent over-fertilizing and reducing production or damaging the plants. If you garden in organic rich soil and add a lot of amendments every year, you might need little, if any, additional fertilizer.
Nancy Szerlag is a master gardener and Metro Detroit freelance writer. E-mail her at szerlag @earthlink.net.