Well-composted soil may supply all the nutrients your plants need, but plan on assisting nature through regular feedings with fertilizer. Proper fertilization is particularly important when growing annuals because bedding plants need lots of nourishment to sustain a continuous production of flowers.
After soil testing has been completed and you know which nutrients and amendments to add, choose from the wide selection available for the task.
Photo Credit: ©2000 Dolezal Publishing/Kyle Chesser
The right amount of fertilizer to use is essential – always read label instructions completely and measure carefully when applying concentrated plant food.
Photo Credit: ©2000 Dolezal Publishing/Kyle Chesser
Measure and mix liquid and water-soluble fertilizers in a clean container, then pour the solution into a watering can for application.
Photo Credit: ©2000 Dolezal Publishing/John M. Rickard
Apply dry concentrated fertilizer granules around the “drip line” of the plant (an imaginary circle drawn straight down from the outer foliage to the ground beneath). Work the granules into the soil with a hand fork or other cultivating tool. Water plants immediately after feeding to dilute the concentrate.
Photo Credit: ©2000 Dolezal Publishing/John M. Rickard
To flourish and bloom, annuals need three basic nutrients – nitrogen, phosphorus and potassium (or N-P-K) – along with small amounts of secondary nutrients and trace elements. The three numbers found prominently displayed on every fertilizer label tell you the percentage by weight of each basic nutrient the product contains. For example, if the package is labeled “10-5-5,” that fertilizer contains 10 percent nitrogen (N), 5 percent phosphorus (P) and 5 percent potassium (K). (Any fertilizer that provides all three of these nutrients is called “complete.”)
It’s best to add any missing nutrients to your garden soil and balance soil pH prior to planting. Performing a simple soil test in your garden will help you determine what nutrients should be added to your planting beds. (Many reliable at-home test kits are sold in garden centers, or you can send a soil sample to a laboratory recommended by your local agricultural Extension office.)
If you don’t have time to test the soil and you’re unsure of your soil’s needs, use a balanced fertilizer such as 10-10-10, which means it has equal quantities of each main ingredient. You can also buy fertilizers that contain secondary nutrients such as calcium and sulfur, or trace elements such as iron and zinc.
Fertilizers are typically available in three forms: granular, which can be worked into the soil or dissolved in water; liquid, which is applied during watering; and foliar, which is sprayed directly onto leaves. (Most liquid fertilizers can double as foliar fertilizers, but always read the product label before use to be certain.) In addition, fertilizers are generally available in organic (natural) and synthetic (chemical) forms.
Plants absorb most of their nutrients from the soil, so your first job is to make sure that you’ve provided them with a well-conditioned, amended soil bed with compost or other organic material and that you’ve balanced your soil’s pH level. (If soil is too acidic or too alkaline, plants can’t absorb the nutrients they need). Most soils also need added nitrogen since it’s steadily depleted. Supplementing with phosphorus and potassium, which are usually more stable in the soil, may or may not be necessary.
As you prepare your garden, dig in well-rotted manure and abundant organic compost, along with either lime or sulfur (as your soil’s pH needs dictate). An inch or two of compost breaks down slowly, enriching soil over time, and also improves workability and texture. If you’re planting annuals between perennials or shrubs, add some compost and a little fertilizer into each planting hole.
Organic fertilizers should be incorporated into garden soil before planting because they release their nutrients with the help of soil bacteria, decomposing slowly and providing nutrients to the plants’ roots for weeks or months. Organic fertilizers provide significant environmental benefits: They break down slowly and tend to remain in the soil instead of leaching or washing into local water sources; they also support earthworms and beneficial microbes.
Synthetic chemical fertilizers generally are less expensive and more quick-acting than organic ones, but they have to be applied more frequently and may burn your plants. If you decide to use a chemical fertilizer, choose a slow-release version designed to disperse nutrients gradually. Such mixtures may last you the entire season and will avoid some of the environmental problems common to quick-release formulations. Look for a product that has at least half of its nitrogen in slow-release form, and note the temperature required for effectiveness. (Many don’t activate until the soil temperature exceeds 75 degrees F.)
Even annuals planted in a well-prepared bed should be fertilized every month or two as they grow. Dwindling flowers or yellowing leaves often signal a need for more nitrogen. Always water thoroughly after fertilizing – when soil is too dry, concentrated fertilizer can burn plant roots.
Finally, keep in mind that too much fertilizer is far worse than none at all for most annuals. Overfertilizing can damage – or even kill – flowers, may leave foliage dry and with burned edges, or can promote leggy and weak growth. In the case of too much nitrogen, plants will produce lush foliage, but at the expense of blooms.
Remember also that, occasionally, any fertilizing can be too much: If you feed plants like love-lies-bleeding, spider flower, treasure flower, nasturtium and moss rose, you’ll end up with no flowers at all. It’s a rare annual that requires fertilizing more than once a month. (Container plants are an exception.) But keep in mind that frequent waterings wash nutrients from the soil. If you’re unsure whether to fertilize your bedding plants, take the safest route and simply observe how they’re doing in the garden. A dose of fertilizer judiciously applied is usually the best course of action if plant growth or flowering seems to be flagging, or if foliage color and bloom numbers are fading. You can also visit the Learn2Grow Plant Database and look up the plants that are growing in your garden for more information. Every plant entry in the database offers fertilizing and general care tips for that particular species.
Established plantings should be fertilized regularly throughout the growing season (except for varieties that prefer low-nutrient soils). Organic fertilizers, including fish emulsion and compost, are low-yield, slow-release sources of vital nutrients; apply them every two weeks. Concentrated synthetic fertilizers may be applied monthly. Whichever type you choose, always read the package label completely, measure carefully and follow all instructions for proper, safe application.
