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How to Fertilize Flowering Plants
Fertilizing Flowers
Choosing the right fertilizers and applying them correctly help all flowering plants grow, thrive, and bloom. The timing of first applications is also critical.
With proper application, plants grow equally well on natural, organic, inorganic, or manmade fertilizers. Similarly, it makes little difference to the plants whether fertilizers they receive are in liquid, solid, granular, or foliar form [see: Fertilizing Flowers and Bulbs].
Providing your plants receive all the main nutrients they need along with a good sampling of most micronutrients and trace minerals, they’ll develop and bloom beautifully in your garden or landscape flower plantings.
That’s not to say than all these fertilizer choices are equal in every regard, however. There are ethical, economical, and ecological differences to consider.
One may choose a completely natural, organic fertilizer made from non-renewable minerals, peat, or bird guano deposits that—once mined out—will be gone forever.
On the other hand, a synthetic fertilizer made from recycled green (vegetative matter) and brown (manure) may be fully sustainable. The same is true for algae supplements made of renewable resources such as kelp.
So, as you might imagine, the choice of the fertilizer to use on your flowers is a decision worth consideration.
Just know that—as far as the plants are concerned—that decision makes little difference provided that the choice gives your flowers the nutrition they need to become and stay healthy.
Even so, here are some important facts about organic fertilizers worth remembering:
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- Organic fertilizers have many benefits. They are naturally occurring. Many contain organic and mineral ingredients that are produced as recycled waste from plants or animals. Some are mined from ancient mineral deposits.
- They often have trace elements and micronutrients besides the three main macronutrients, nitrogen, phosphorous, and potassium.
- They decompose slowly, releasing their nutrients over time. That avoids the hazard of fertilizer burns to foliage that sometimes happen with more concentrated formulations.
- Organic fertilizers are gentle to the environment.
- Since organics contain less nutrients by weight, applications may have to be made more frequently to meet the needs of your green and growing plants.
Timing Fertilizer Applications
Timing fertilizer applications is really a matter of knowing when to start, then following a schedule of applications through the season.
Flowering plants that overwinter—evergreen and deciduous biennials, perennials, and bulbs—usually require fertilizer applications in spring to help them feed new growth of foliage and flowers. The first application should take place once active growth begins, but avoid jumping in as soon as you see fresh shoots.
Early applications usually use so-called “flower fertilizers”—often high in nitrogen and low in phosphorus and potassium. Nitrogen spurs foliage growth, and is water soluble. If applied before soils thoroughly warm, however, it may chemically burn tender young foliage and vital hair roots.
Wait to make first flower fertilizer applications until garden soils warm to at least 60°F (16°C) at a depth of 6 in. (15 cm), typically at the onset of the mid-spring period about four weeks after first buds break and new shoots appear. The fertilizer will rapidly become available for uptake into the plants and help them fill out foliage and begin to set flowers.
Thereafter, apply balanced—10–10—10 formulation—fertilizers at 4–6 week intervals or as directed for the species. Potassium and phosphorus aid the plants to develop strong flower shoots and prepare to set seed by providing nutrients as their roots work overtime to fuel growth of both foliage and flowers.
Fertilizer Application Options
The proper methods of applying fertilizer to flowering plants boil down to two things: When to fertilize and how to fertilize.
It’s always best to work your fertilizers into the soil soon after application, even when applying a liquid.
A hand fork spreads out granules or liquid-fertilizer wetted soil, mixing the fertilizer into a larger volume of soil.
Mixing prevents burning flower leaves or foliage with too much nitrogen.
Always follow up fertilizer applications by giving your plants a thorough watering. Applying water to the soil over their roots further dilutes the fertilizer and carries it deeply into the soil and your flowers’ roots.
Step-by-Step Instructions
Fertilizer Application Choices and Options
Fertilize new plantings of flowering plants when the seedlings or transplants are fully established and begin rapidly growing.
That’s often in spring, but it may also be in mid-season for gardens planted with successions of blooms from different plants [see: Planting Flower Successions].
Fertilize landscape plantings every other month throughout the growing season until flower formation slows or stops. Fertilize container plantings every 4–6 weeks while plants are actively growing and producing flowers.
Avoid fertilizing perennial flowers at the end of their flowering season. Too much nitrogen then risks promoting new growth that is damaged easily by frost.
Always measure amounts—too much fertilizer is worse than no fertilizer at all.
Apply dry, granular or encapsulated fertilizers along the plant’s drip line, an imaginary circle on the soil straight down from the edge of each plant’s foliage.
Always water the soil under the plants well after applying fertilizer.
Choose a fertilizing method from those demonstrated here, and follow the directions shown for each fertilizer type:
How to Apply Different Fertilizer Types
Prepare
Measure carefully and apply granular and encapsulated fertilizer according to its package-label directions.
Apply
Spread or scatter the granules evenly on the soil in a circular pattern along the edge of the plant’s drip line.
Use a hand fork or cultivator to mix fertilizer into the top 2 in. (50 mm) of soil.
Water thoroughly after application to dissolve and dilute the fertilizer immediately after application.
Apply powdered dry fertilizers by spreading a layer of fertilizer around the base of the plants.
Follow the application directions on the package label for both organic and synthetic dry powdered fertilizers.
Work the fertilizer into the soil.
Water in the fertilizer after application.
Fish Emulsion and Other Liquid Fertilizers
Dilute liquid fertilizer with water according to its package-label directions.
Apply the diluted mix of fertilizer and water over the plant’s root zone.
Foliar Fertilizers
Water-soluble foliar fertilizers are absorbed directly by plant leaves and leaf stems.
Apply the liquid foliar fertilizer with a hose-end sprayer.
Fertilize on wind-free days cooler than 85° F (29°C).
Prepare
Read and closely follow all package-label directions when measuring and applying granules of concentrated encapsulated fertilizer.
Always carefully measure and apply the recommended amount.
Apply
Sprinkle encapsulated fertilizer on the soil surface around the plant’s drip line.
Use a trowel or hand fork to mix the fertilizer into the top 2-in. (50 mm) of soil, without disturbing plant roots.
Water thoroughly immediately after application.
Warning:
As a health and safety precaution, always wear waterproof gloves, a dust mask, and eye protection when mixing and applying fertilizers to plants.
Read completely, note any warnings, and follow exactly all package label directions when opening, mixing, and applying garden fertilizers.
Fertilizing Container Flowers
Because flowering plants in containers have limited soil, fertilizing is a necessary part of their care.
It’s best to feed your container flowers on a regular schedule, tailoring the fertilizer to the plant.
Some species require acidic fertilizers, while most do not.
Choose either method shown, gather your materials and implements, and follow these easy steps:
How to Apply Granular Fertilizer to Container Plants
Always thoroughly water your foliage and flowering plants in containers the day before you apply granular fertilizer.
Carefully measure the fertilizer, reading completely and following exactly the fertilizer package directions.
Spread the fertilizer evenly on the container’s soil surface, leaving a gap between the plant’s stem or growth point and the fertilized area.
Use a small hand fork to work the fertilizer into the soil, cultivating it.
Apply water after fertilizing.
Allow the container to drain.
Warning:
As a health and safety precaution, always wear waterproof gloves, a dust mask, and eye protection when mixing and applying fertilizers to plants.
Read completely, note any warnings, and follow exactly all package label directions when opening, mixing, and applying garden fertilizers.
How to Apply Foliar Fertilizer to Container Plants
Foliar fertilizers may be powdered or liquid concentrates.
Dilute the foliar fertilizer with water to its recommended strength, reading completely and following exactly the package directions.
Fill a hand applicator bottle or sprayer with the dilute fertilizer mixture.
Spray a mist of dilute foliar fertilizer solution onto the plant’s foliage and stem.
Apply fertilizer until the foliage is wet, begins to form droplets, and runs off the leaves and stems.
Water the plant after applying fertilizer, but avoid wetting its leaves or leaf stems.
Allow the soil to drain.
Foliage should be completely dry before exposing it to direct sunlight.
Warning:
As a health and safety precaution, always wear waterproof gloves, a dust mask, and eye protection when mixing and applying fertilizers to plants.
Read completely, note any warnings, and follow exactly all package label directions when opening, mixing, and applying garden fertilizers.