Flower Power: When to Apply Flower-Boosting Elements

By Chris Bond
Published: July 19, 2021
Key Takeaways

The bloom phase is an important stage for your plants to reach their potential. The nutrients you give them at this key time can make or break your garden.

Few things in the garden are so rewarding as lush, colorful flowers. While some soils and growing mediums have ample nutrients to make this plant performance happen all on its own, many lack just the right combination that allow your plants to live up to their full botanical potential. Knowing some basics about what fertilizers to use and when to use them will help ensure you give your plants just what they need at the right time to enjoy their beauty to its fullest.


Flowering Basics

All plants need some combination of nutrients and minerals to achieve their biological destiny. They need them all in proportionate ratios as well. It is entirely possible (and fairly common) to have almost all of what your plant needs but be just shy of the right amount of one element that seems to keep your plants from peaking. For example, you may have a lush, bright-green, full, thriving flowering plant that never seems to actually flower. This could be because it is getting copious amounts of nitrogen which the leaves just love, but this high amount of nitrogen is impeding your plant’s ability to form flower buds. While nitrogen is critical for your plant’s production of chlorophyll, other elements like potassium are also needed and help regulate various other metabolic processes in the plant, including bud and flower development.

For those needing a quick refresher from middle school biology, photosynthesis is the process plants use to make their own food. Without this process, most plants could not have what they need to flower. Nitrogen is needed to make chlorophyll, promote leaf and stem growth, as well as fruit and seed growth. Phosphorus, the element most closely associated with blooms, supports the flow of energy and nutrients throughout the plant to help with root development and flowering. Potassium is helpful for overall metabolic processes and is also needed for fruit and seed development. It is important to note when there is not enough nitrogen in the soil, plants struggle to get enough phosphorus, even if it is present in sufficient quantities.


Grower adding fertilizer to watering can.

Types of Fertilizers for Blooms

Many commercially available fertilizers are “complete” fertilizers, meaning they contain some ratio of the main nutrients (the macronutrients) all plants need to thrive. In the typical three-number system (e.g., 10-6-4 or 24-8-16) each number represents the percent of nutrients in each bag or container. They always appear in the order of nitrogen (N), phosphorus (P), and potassium (K). A proper ratio of each for the type of flowering plant you have is critical to obtaining the ultimate blooms on your plants. Fertilizers marketed specifically for flowering plants tend to have higher amounts of the middle number, phosphorus (P). Blooming plants need lots of phosphorus to nourish their blooms and keep them blooming. If they do not receive enough P during this time, they will cease to bloom.

Bloom-boosting fertilizers come in various forms. It is important to know the differences as they do not all start working and releasing nutrients at the same time. There are chemical and organic forms, granular and liquid forms, and water-soluble and non-soluble forms. Organic fertilizers are formulated using only animal, plant, or mineral elements and are the only kind of fertilizer allowed for certified organic gardening. Chemical fertilizers can be petroleum-based or any formulation of elements that include any man-made derivation of elements. Granular forms can be either water soluble or not and will take longer to break down than liquid forms of fertilizer.


(Read also: Transition to Bloom Phase: When & How to Switch)

Often, organic fertilizers are not water soluble. They are broken down and activated by microbial action in the soil which then releases the nutrient package. They take longer to work than most chemical fertilizers, but often all their payload is utilized. Chemical and water-soluble fertilizers tend to work quickly, but any unused nutrients are leached out or otherwise wasted. Any of these forms can work when applied at the recommended times.


A word of caution should be noted here in regard to fertilizers designed to aid in blooms. If they are not given to plants at the right time when needed, the plants will not use all of the phosphorus and potassium and they can run off or leach out and end up in waterways. A condition known as eutrophication can be created when too much phosphorus is introduced to aquatic environments. This causes algae to bloom which increases bacteria production, which removes oxygen from the water, which in turn is detrimental to fish and other aquatic species. Environmental harm from excess phosphorus is not limited to waterways though. In field and garden soils, too much phosphorus can prevent the growth of beneficial mycorrhizal fungi. This means it is critical to not over fertilize with bloom boosters or to not use them at times when your plants cannot fully utilize their full values.

Blooming flower

When to Fertilize for Blooms

Not all flowers are created equal. Some are right out there for all to see, big and bold; others are much harder to discern. Some seem to open right while away others take their sweet time. Regardless of what flowering plant you have, applying flower-supporting nutrients at the right time will help you to achieve gorgeous blooms. At the first sign of bud development, it’s a good idea to give your plants a boost of nutrition. It should contain appropriate amounts of phosphorus to assist in this stressful time for the plant and to ensure metabolic functions continue properly throughout your plant’s vascular system.

Precise timing of applications will depend on your region, but in general the following timelines are applicable to achieve optimal blooms:

Flowering bulbsSpring blooming: feed at recommended amounts during planting in the fall and again at the first sign of emergence in the spring. Summer blooming : feed at recommended rates at planting time. For bulbs in their second and subsequent years, feed once growth begins in the spring. Feed again once bulbs have ended their blooming cycle. For bulbs with summer-long blooming periods like dahlias, cannas, and Asiatic lilies, give them another dose of bloom-boosting fertilizer around the middle of July.

Annuals — Apply nutrients at the time of bed or pot preparations. Give annuals another dose in another six to eight weeks. If you have annuals that bloom into the fall, an additional dose of bloom-boosting fertilizer can be given in mid to late August.

Perennials — For new plantings of flowering perennials (flowering grasses too), apply just like for annuals, at the time of bed preparation. Another dose can be given six to eight weeks later. Unlike annuals, perennials need a resting period, so do not fertilize after early summer. For established plantings, apply the first dose in the spring when new growth appears and then again about two months later, a second application of bloom-supporting nutrients should be applied.

(Read also: How to Prepare the Best Soil for Your Flower Beds)

Roses — Like perennials, roses should not be fertilized at all after early summer. Any nutrients given after this point could encourage new growth that will not survive the colder months. Nutrients should, however, be given in succession about every four to five weeks between late April and early July.

Wildflowers and flowering shrubs — in the absence of species-specific nutrient recommendations, a bloom-encouraging fertilizer can be applied once new growth appears in the spring.

Indoor flowering plants — during the blooming period, feed can be given to houseplants every two weeks. When not in bloom, you can give them half of the recommended rate throughout the year every other week to once per month. This can encourage additional blooms without overfeeding the plants.

Soil Testing and other Considerations

Remember that too much of anything, even a good thing (including pure water), can be toxic. Giving your plants just the right amount of needed nutrients at the right time will pay dividends in the form of beautiful blossoms. Giving them too much will thwart your best efforts. They need the right amount of each nutrient to perform each function of their lifecycle. Besides blooming, this includes root, stem, and leaf development as well as seed and fruit development Before adding any amount of any type of fertilizer, for flowers or otherwise, it is important to have a soil test done to know what your current nutrient levels are.

Soil testing is not difficult or expensive. Most garden and home centers offer relatively inexpensive DIY kits to test your soil or planting media. Thousands of videos online will show you how to do it if you are unsure. If you do not want to do it yourself, sending a sample to a lab is equally easy and still not that expensive, depending on the types of testing performed. Your local or regional cooperative extension or state testing lab can perform this analysis for you so you will know whether or not your soil or growing medium has the right elements needed for optimum blooms to begin with. Only then will you have the basis of information needed to decide if you should add any additional nutrients or fertilizers to help get the blooms of your dreams.


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Written by Chris Bond | Certified Permaculture Designer, Nursery Technician, Nursery Professional

Profile Picture of Chris Bond

Chris Bond’s research interests are with sustainable agriculture, biological pest control, and alternative growing methods. He is a certified permaculture designer and certified nursery technician in Ohio and a certified nursery professional in New York, where he got his start in growing.

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