> Next: Fertilizing Flowering Plants
Nutrients and Feeding Flowers
In This Section
In this section, you’ll find discussions on fertilizing flowering plants and bulbs in flower gardens and step-by-step demonstrations, including:
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- How to choose fertilizers and properly apply them to your flowering plants in your home garden or landscape.
- How to choose fertilizers and properly apply them to bulb plantings in home landscapes and gardens.
On This Page
Here, you’ll find discussions of the nutrients plants and bulbs need, fertilizer options, and best practices for providing the right amounts to your flowers and bulbs, with the following subjects beneath each of these titles:
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- Fertilizers and Flowers
- Applying Fertilizers to Bulbs
- Nutrients, Micronutrients, and Trace Minerals
- Nitrogen
- Phosphorus
- Potassium
- Micronutrients and Trace Minerals
- Organics and Organic Compost
Fertilizers and Flowers
Flowering plants need regular applications of fertilizer to grow, keep their vigor, remain healthy, and produce beautiful flowers.
Fertilizers applied during preparation of soils and during planting provided the nutrients to establish strong root systems and promote early growth of your flowers and bulbs [see: Preparing Garden Soil for Flowers, Preparing Soil for Bulbs, and Soil for Flowers in Containers].
Most flowers benefit from fertilizer applications at regular intervals throughout the blooming season. These feedings should end when flowering stops, or when bulbs or perennial plants slow their growth and become semi-dormant.
The formulation of fertilizers applied for seasonal feedings are often different than those added to soils during planting. Starter fertilizers typically have more phosphorus and potassium to promote root growth than do in-season, balanced blends.
Look at the label on fertilizers. Most contain a 3-number NPK code, such as 12–12–12, to show the amount of available nitrogen (N), phosphorous (P), and potassium (K) they contain by weight.
The NPK assay numbers are always lower on organic fertilizers, because they contain breakdown products of seaweed, mined natural minerals, manure or compost as source ingredients, and those sources are less concentrated than manmade, or synthetic, fertilizers.
It may be necessary to apply organic fertilizers more often, or in greater quantities than the amounts recommended on the labels of synthetic fertilizers to deliver the same amount of nutrients to your plants.
On the other hand, organic fertilizers contain many micronutrients and trace elements plants also need. Those are missing from synthetic fertilizers unless specifically added by the manufacturers.
Strong, healthy flowers shrug off most pests and plant diseases [see: Flower and Bulb Pests and Diseases].
Applying Fertilizers to Bulbs
Flowering plants and bulbs have different nutrient needs and times of application. Take time to understand these differences [see: Fertilizing Flowering Plants and Fertilizing Bulbs].
Before you apply fertilizer to your bulb plantings, always read completely and follow exactly all the package directions found on the label of each fertilizer.
For solid or dry fertilizers, use a hand fork or a garden rake to work the fertilizer or granules into the soil after they are applied. Mix it into the top few inches of soil around the plant, avoiding damaging their roots.
Water thoroughly immediately after you apply solid fertilizers. This helps dilute, dissolve and spread the nutrients they contain. Mixing, spreading and diluting prevents foliage and root burn.
Many gardeners combine this process with cultivating, to uproot any sprouting weed and loosen the surface of the soil.
Apply liquid fertilizers after cultivation is completed. The liquid will be absorbed into the soil and will penetrate slowly to the roots.
For beds with mulch, rake the mulch aside in sections, apply the fertilizer, then work it into the top few inches of soil.
Apply foliar fertilizers, special liquid fertilizers that are absorbed directly by the flowering plants’ foliage and stems, by spraying them with a hose-end applicator onto the plants early in the day after temperatures have warmed.
Always use safety and health precautions when applying fertilizers. Wear gloves, eye protection, and protective clothing.
Safely dispose of empty containers and unused fertilizer as directed. Wash protective clothing separate from other laundry.
Nutrients, Micronutrients, and Trace Minerals
Good flower gardeners know how their flowering plants and bulbs use the fertilizers they apply and how to recognize a struggling plant’s needs for one or more specific nutrients.
There are three major nutrients all plants use. They are Nitrogen, Phosphorus. and Potassium.
Nitrogen
Nitrogen is essential for every green plant to grow foliage. Deep within the cells of your flower’s leaves, in the presence of sunlight, carbon dioxide, chlorophyll, and nitrogen, tiny cellular factories build plant proteins and sugars through photosynthesis.
The nitrogen plants use is not the familiar gas found abundantly in the atmosphere. Instead it is two specific forms of nitrogen salts, NO2 and NO3, combinations of an atom of nitrogen and one or two atoms of oxygen.
Both nitrogen salts are water-soluble. They are carried by osmosis into your plant’s roots, up its stem in sap, and into its leaves.
Photosynthesis releases oxygen through pores in the leaves when the nitrate and nitrite salts become proteins sugars. Every flowering plant is a tiny factory that processes nitrogen so they can grow.
Apply too much nitrogen, and a flowering plant will develop luxurious foliage but few flowers.
The photosynthesis process is very dependent on two trace minerals, iron and magnesium. If soils become deficient in either, the process falters and slows. Leaves turn from green to a sickly yellow, a deficiency called chlorosis.
When your plants are receiving plenty of nitrogen but fail to green up and develop new foliage, the answer may be to add fertilizers rich in iron and potassium, or to acidify soil that is too alkaline.
Phosphorus
Phosphorus plays a different role than nitrogen. It spurs root growth, flowering, and setting seed. It is not water soluble, and it tends to bind to soil minerals making it unavailable for your flowers to use.
Phosphorus plays important roles in photosynthesis, including storing and transferring energy and aiding foliage respiration that eliminates waste products from leaf pores, among various other plant activities.
Applying fertilizer with phosphorous is one way to increase the amount available for your plants. Soil cultivation also helps move phosphorus that is present in surface layers down into the soil and near plant roots.
Frequently, annual and perennial flowers that produce few flowers will become covered with blooms after gardeners apply fertilizers with phosphorus. Instead of a balanced fertilizer—one with equal parts of all three major nutrients—choose a fertilizer with more phosphorus, such as 2–5–2.
Potassium
Potassium regulates the static pressure of water in plants—in short, it keeps them from wilting. It performs this function by helping the plant open and close its leaf pores, or stomata. Like phosphorous, potassium is not water soluble and tends to bind to soil minerals.
Because movement of water is so important to your flowering plants, it also helps carry water, sugars, and proteins around the plant from the leaves where they are manufactured in photosynthesis to the stem, roots, and flowers.
Plants stressed by heat, drying winds, or too little irrigation often need extra potassium to help them cope and restore their vigor. Applications of fertilizers formulated with extra potassium—such as 2–2–5—along with soil cultivation both move available potassium down into the root zone.
Micronutrients and Trace Minerals
Besides the big 3 major nutrients—nitrogen, phosphorous, and potassium—there a a score of still-important but lesser known micronutrients and trace minerals that play roles in plant and flower health, vigor, and growth.
Few synthetic fertilizers contain these components. Fortunately, organic compost and decomposed green plant material and animal manure both are rich in them.
You already know that compost and organic material improve the texture and drainage of garden soils [see: Preparing Garden Soils for Flowers].
You’ll now find that they have the added benefit of replacing lost micronutrients, trace minerals, and—importantly—soil microbes, beneficial bacteria, and other microorganisms.
Organics and Organic Compost
Millions upon millions of these tiny animals, fungi, and bacteria live in every bit of your garden soil. They help break the bonds of soil minerals to nitrates, potassium, and phosphorous, freeing them so your flowering plants can use them to grow.
They also help organic decomposition, slowly freeing more soil nutrients without the need for fertilizers. Whenever you amend your soil with compost or apply organic mulch, you add untold billions of beneficial soil microbes to your flower beds.
So, what roles do these micronutrients and trace minerals play in your flower garden?
These valuable nutrients fall into several categories. Some are vitamins. Others are catalysts that play roles in photosynthesis or cell regulation within your plants. Some are reagents that bind or break chemical bonds between other nutrient molecules.
Some microorganisms even enrich your garden soil, such as the bacteria found on the roots of legumes (members of the pea and bean families) that enable those plant manufacture their own nitrogen.
All these nutrients, micronutrients, trace minerals, and microorganisms in your soil contribute to the beauty of your flowers and the health of your plants.