Fertilizing

Vegetables and
Annual Flowers

Class 1: Gardening Basics
Class 2: Garden Planning & Design
Class 3: Indoor Seed Starting
Class 4: Planting & Transplanting
Class 5: Maintaining a Healthy Garden
Class 6: Troubleshooting

One of the most common questions posed by gardeners is "How and when should I feed my plants?" Technically speaking, you aren’t exactly feeding plants -- they manufacture their own food through photosynthesis. But you are providing the mineral nutrients they need to do this.

There are two ways of approaching the task of fertilizing. Organic gardeners have a saying, "Feed the soil, and the soil will feed the plants." Thus they focus on amending the soil with naturally occurring materials like compost, leaf mold, and rock powders. These materials don’t nourish the plants directly; rather, they are broken down by soil microorganisms that, in turn, release nutrients in forms available to plants. As we said earlier, healthy soil, teeming with life, is the foundation for optimum plant growth.

Non-organic, or synthetic, fertilizers work a little differently -- they feed the plants directly. Most of the commercial, water soluble fertilizers you see are in this category. They provide a direct source of nitrogen (N), phosphorus (P), and potassium (K) to the plants in a form they can use immediately, bypassing soil microbes.

When to Fertilize
If you apply a generous amount of compost or aged manure to your garden each spring, you may need little or no supplemental fertilizing, especially in flower gardens. However, very vigorous annuals may need some supplemental fertilizing to give them the energy to produce abundant flowers all season long.

Vegetables often respond well to judicious applications of fertilizer. You have a number of options here. You may want to apply a dilute solution of fertilizer once a week; this is especially helpful to plants growing in sandy soils, since these soils don’t hold nutrients well. Or you can focus your fertilizing efforts when plants need it most by applying fertilizer at the recommended full strength a few times during the season. Timed applications for a long-season crop like tomatoes might consist of fertilizing two or three weeks after transplanting, fertilizing again when plants begin to bloom, then again when fruits begin to develop, and finally two weeks after the first harvest.

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Deciphering Fertilizer Labels

What does "5-10-10" on a fertilizer label really mean?

These numbers represent the ratios of three plant nutrients: nitrogen, phosphate, and potash. (Phosphate is a compound containing phosphorus; potash is a form of potassium.)

Our 5-10-10 fertilizer contains 5 percent nitrogen, and ten percent each of phosphate and potash.

A fertilizer containing all three of these nutrients -- nitrogen, phosphorus, and potassium -- is called a complete fertilizer. (There are many other important plant nutrients, but these three are needed in relatively large amounts.)