Gardening: How to Feed Flowering Annuals

By The National Gardening Association, Bob Beckstrom, Karan Davis Cutler, Kathleen Fisher, Phillip Giroux, Judy Glattstein, Mike MacCaskey, Bill Marken, Charlie Nardozzi, Sally Roth, Marcia Tatroe, Lance Walheim, and Ann Whitman from Gardening All-in-One For Dummies

Feed the flowering annuals in your garden to help them grow vigorously, build healthy foliage, and ensure spectacular blooms. If any nutrient isn’t present in the soil in sufficient quantities, or is present in a form that the plant can’t absorb, you must add it as fertilizer or correct the conditions that are prohibiting nutrient absorption.

Luckily, most soils already contain enough nutrients for healthy growth. But if your annuals aren’t producing their quota of blooms, the soil doesn’t contain enough nitrogen. Luckily, plants usually respond quickly to nitrogen application, so nitrogen deficiency is easy to correct by simply adding fertilizer.

Nitrogen is often the only nutrient that you need to apply as a fertilizer. Soil tends to be nitrogen-deficient because plants use more nitrogen than any other nutrient, quickly depleting nitrogen supplies.

In addition to nitrogen, phosphorus and potassium play important roles in plant growth:

Phosphorus is associated with good root growth and with flower, fruit, and seed production.
Potassium is necessary for healthy roots, disease resistance, and fruiting. Only a soil test can identify deficiencies in either of these nutrients. Because phosphorus and potassium are less mobile than nitrogen, you have to work those nutrients into the soil at planting time. That way, they’re located right where the roots can absorb them.

Consider these fertilizing tips for the flowering annuals in your garden:

The best time to start fertilizing your flower bed is before you start planting. For the best results, add your fertilizer no more than a day or so before planting. You can add organic matter at any time. Some gardeners prefer to start cutting back on nitrogen after their annuals reach full bloom, thinking that the nitrogen may force leaf growth at the expense of flowers. If you’re tending annual flowers properly, by removing spent blooms, consistent applications of nitrogen throughout the life of the plant result in more blooms.
Don’t fertilize dry plants. Plants need water to move fertilizer nutrients to the roots and help them take these fertilizers up into the plant. Without adequate water, the plant roots that do contact the fertilizers may be burned, causing the roots to die and the plant to suffer.
Avoid overfeeding. Overfertilizing can be much worse than not applying enough fertilizer. Excess nitrogen, for example, can burn the edges of leaves and even kill a plant.