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7 Best Fertilizers for Irises – A Buyers Guide

7 Best Fertilizers for Irises – A Buyers Guide

Named after the Greek goddess, Irises are beautiful flowering plants. There are about 300 species with showy flowers in different colors.

The word Iris means rainbow representing the colorful flowers. Irises are a common ornamental plant in many locations, and they are my favorite garden plant because of the delicate flowers and easy care schedule.

This rainbow plant will not just add charm to your garden but also attract wildlife like hummingbirds and butterflies.

You can even use the bright blooms to add fragrance and color to empty vases in your house. 

Irises are very attractive and graceful but providing proper plant care is the key to keeping them happy and thriving.

Once the natural soil nutrients deplete, fertilizer is the vital source of nutrition, especially for flowering varieties like Irises.

This plant can easily reach a height of 2-3 ft (0.6-0.9m) and repeatedly bloom with the right fertilization schedule.

You’ll find several fertilizers for flowering plants online and in stores which makes it difficult to choose a single fertilizer for Irises.

This guide includes the best fertilizers for Irises and other important information regarding Irises’ fertilization.



Best Fertilizer for Irises


Performance Organics Blooms Plant Nutrition by Miracle-Gro – Best Overall Irises Fertilizer

This is one of the most fast-acting plant food for flowering plants since it starts showing results within the first week of application.

So whether you forgot to fertilize your Irises early in the season or they need a quick boost of nutrition, this fertilizer is the answer for everything.

With the NPK ratio of 5-7-10, your Irises will produce more blooms, and the color of the flowers will also enhance.

This fertilizer should be applied in dry form; therefore, do not mix it in water before application. But you should water the soil thoroughly after adding fertilizer to start the feeding.

Do not let the fertilizer touch the foliage or the plant stem.

Detailed application instructions for containers and in-ground plants are listed on the back of the bottle, which makes fertilization easier for beginners and experienced gardeners.

Like other fertilizers by Miracle-Gro, this one is also part of the organic gardening OMRI list.

This 2.5 lb package can cover 165 sq ft of garden area. And you should repeat the application every 4-6 weeks for healthy foliage and flowers.



  • Results in bold blooms with vibrant colors
  • Comes in granular form for easy application
  • Made from organic and natural ingredients
  • Six months money back and no burn guarantee
  • Can be used for any ornamental plant variety



  • Not for hydroponics
  • Has an unpleasant smell
  • Customers complained about mold and mushroom growth on indoor plants
  • It attracts flies, bugs, and even pets like dogs are attracted

Learn more about this fertilizer here.


Container and Bedding Plant Fertilizer Spikes by Jobe’s Organics – Best Irises Fertilizer Spikes

These pre-measured fertilizer spikes are an easy solution for fertilizing Irises growing in containers or garden beds. This pack of 50 spikes provides all nourishment required for Irises at the root level.

The NPK ratio is 3-5-6, which means these spikes can be used throughout the season for the growth and nourishment of Irises.

Apart from the macronutrients, these spikes also contain bone meal, feather meal, healthy bacteria, and microorganisms. This unique combination of products results in a faster breakdown of nutrients in the soil.

With regular application, your Irises will develop drought, disease, and pest resistance.

It’s important to note that this organic product is formulated to prevent waste of nutrients or runoff. It is listed by OMRI for organic gardening and production.

According to Jobe’s, these spikes are designed specifically for annual or perennial flowering plants, but you can use them for foliar plants as well.

I have been using these according to the instructions on the package, and the Irises in my garden are thriving and blooming repeatedly.

Since they are pre-measured, the risk of over-fertilizing is low, and you will never burn your plants.

Place the spikes in the soil while planting them or when the growing season begins. For beautiful flowers and optimum growth, the application should be repeated every 6-8 weeks.

For container plants, the number of spikes depends on the container size. For bedding plants, use eight fertilizer spikes per sq ft.



  • Environment friendly with easy application and resealable bag
  • Guaranteed nourishment for root growth
  • Safe for pets and children
  • Promotes microbial action in the soil, abundant blooms, and green foliage
  • Suitable for any type of container or bedding plant variety
  • Organic
  • Works on seeds, new plantings, and established plants
  • Contains bone meal and Biozome



  • Mold growth
  • Pets are attracted to the soil after fertilizing
  • Some customers complained about receiving crumbled spikes

Don’t forget to check out this wonderful product here.


Bulb Food by Jobe’s Organics – Best Granular Irises Fertilizer

If you are looking for something that helps your Irises produce more blooms, you should definitely try this granular fertilizer. It is not only organic but a dedicated plant food for plants growing from bulbs.

This fast-acting fertilizer is suitable for any bulb flowering houseplant. I have used them for potted Irises, and they produced lovely blooms with rich color and fragrance.

This granular bulb food will also enhance the root mass, improve plant resistance to unfavorable conditions and soil health.

The fertilizer analysis for this Jobe’s product is 3-5-4, which is guaranteed to help your Irises bloom abundantly and improve the soil condition.

There are other ingredients as well, such as bone meal, feather meal, manure, and sulfate of potash.

The Archaea found in this fertilizer is scientifically proven to clean to soil. Other fungi will increase the root system’s nutrient and water absorption capacity.

You can repeat the application every 3-5 weeks or depend on your plants’ needs.

The best time for adding this fertilizer is while soil preparation, and make sure you mix it in the soil below the bulb.



  • Enhanced with natural ingredients and Jobe’s Biozome that keep the nutrients close to the root zone
  • Contains no harmful chemicals
  • Listed by OMRI and USDA for organic production
  • Applicable for both new and existing flowering bulbs
  • Human and pet friendly
  • Can be used for other bulb flowerings like Lilies, Daffodils, or Tulips.



  • Has a strong smell that might be disliked by some people, especially when used for indoor Irises

If this is the product you’re looking for, click this link here.


Bone Meal All Natural Plant Food by Espoma – Best for Budget Irises Fertilizer

This is an economical fertilizer for Irises, especially if you have lots of them in your garden or pots. A single 4 lbs package retails for US$ 8.52 and lasts for several applications.

This is a bone meal-based plant food, so it supplies organic phosphorus and nitrogen for flowering houseplants. It contains domestic bone meal with no fillers.

The bone meal will strengthen the root system and promote growth.

You have to apply it at planting time for all types of new bulbs and perennials. For existing plants, use a spring or fall fertilizing schedule. Mix the fertilizer directly in the soil and water it thoroughly for absorption.

The NPK ratio for this plant food is 4-12-0.



  • Contains 100% pure bone meal, which is an ideal supplement for any type of flowering plant
  • Can be used for bulbs, trees, shrubs, and potted plants in your garden
  • Dissolves in water
  • Organic product



  • The smell can attract animals
  • Lacks detailed instruction about the application

Check out this wonderful product here.


Premium Bloom Flowering Plant Food by EarthPod – Best Eco-friendly Irises Fertilizer

After fertilizer spikes, capsules or pods are the next most creative way to supply plant food.

EarthPods is well known for its fertilizer capsules for different plant varieties. This one contains special flowering plant formula that boosts blooms.

The main goal of this EarthPods is to create natural products with minimal impact on our planet.

So if you want to support a brand that is plant and environment-friendly, this is a must-have product. Their premium fertilizer formula replicates the natural soil to help plants thrive.

You can use it for bulbs, annuals, perennials, or flowers growing in hanging baskets.

It ensures mess-free fertilization for any flowering plant variety growing anywhere.

These capsules can help improve flower color, size, and root development. You can use it for other flowering plants like Roses, Begonia, Poppy, etc.

I highly recommend this fertilizer for in-ground Irises because the application is easy and fast.

You have to just place the capsule in the soil near the center of the plant and water the soil to help the capsule break down the nutrients.

Each pack contains 100 pods that are enriched with humates, trace minerals, root fungi, bacteria, and essential nutrients.

It’s a combination of more than 70 natural ingredients that are guaranteed for better root and flower growth. But for maximum growth, repeat application every 1 or 2 weeks.



  • Good quality plant food for indoor and outdoor flowering plants
  • Does not require any measuring cup or scoop for application
  • Has no weird smell
  • Releases the nutrients slowly to avoid over-fertilization of fertilizer burns
  • Nutrients are distributed in the root system faster
  • Tested and approved by scientists for plants and soil
  • Does not contain urea



  • Time consuming and expensive for large applications
  • Customers complained about lack of information about the application process

Buy this fertilizer on Amazon by clicking here.


Flower Girl Bud and Bloom Booster by Dr. Earth – Best Organic Irises Fertilizer

This handcrafted fertilizer is a perfect bloom booster by Dr. Earth. It’s not just organic but also long-lasting.

In fact, all fertilizers by this brand are recommended for organic gardening because they address and eliminate food safety concerns.

Any type of bulbs, rhizomes, and tubers can be fed using this fertilizer.

It’s safe to use for organic gardening since it contains only natural ingredients, true-biotic, and a special blend of soil microorganisms.

It also contains alfalfa meal, feather and bone meal. If used properly, you will not need any other supplement plant food for your Irises.

Ecto and Endo mycorrhizae present in this fertilizer will increase nutrient availability, plant performance, and tolerance against droughts.

With few applications, the soil will become more fertile and enriched in minerals which in return ensure plenty of blooms and a strong root system for Irises.

The nutrient content in this organic fertilizer is 3-9-4. This improves the buds on flowering plants, and as a result, the Iris will produce bigger and more blooms.

The overall quality of the blooms improves with this product as it ensures consistent nutrition.



  • Organic and made from 100% natural products
  • Ideal for all flowering plants, especially those with bulbs, tuber, or rhizomes
  • Doesn’t contain GMOs or chicken manure
  • Does not cause a growth spike
  • Lasts for several months
  • Contains natural phosphorus



  • Few customers reported pests and mold infection
  • Has a strong, unpleasant scent
  • Not water soluble

Don’t forget to read more about this fertilizer here.


Bulb-Tone by Espoma – Best Bulb Irises Fertilizer

This formula by Espoma is ideal for any spring bulb because it’s rich in organic ingredients and bone meal.

The 18 lbs bag will last for several months and can be used for both spring and fall fertilization.

It contains the special biotone and is rich in macronutrients in the ratio of 3-5-3.

It also contains micronutrients like magnesium, calcium, and sulfur. The Bulb-Tone will not only act as a fertilizer but also plays the role of a soil amendment.

You can use it for new plantings or established bulbs. The quantity will vary depending on the plant size or growth stage, but the detailed instructions are printed on the package.

Few growers have complained that something in the fertilizer attracts their pets that dig up and destroy their plants.



  • Easy application
  • Beneficial for spring and fall bulb feeding
  • Made for organic gardening
  • Naturally bio-degrades in the soil to improve the soil condition



  • Has a stinky smell

View this product here.


What to Look for in a Fertilizer for Irises

Fertilization depends on the variety of Irises, but in my opinion, new varieties require more feeding compared to the old ones.

The following categories of fertilizer are great for growing and blooming Irises.


Organic Fertilizers

With more research and awareness about the harmful impacts of chemical fertilizers, more and more people are shifting towards organic gardening.

Organic fertilizers are an essential part of this gardening practice because they help you replicate the natural soil that is rich in soil microbes.

These microbes help recycle and process dead tissues.

The soil fungi increase the nutrient content for your plant and even fight pathogens.

The main concept behind organic fertilizers is to feed the soil, not the plants. Once the microorganisms in the soil are well fed, they will extract nutrients for the plant.

Since chemical fertilizers are designed to supply nutrients in large quantities, they disturb the natural environment of the soil microbes.

They damage the soil ecosystem, and eventually, the microorganisms might die. Chemicals fertilizers also damage waterways as they cause nutrient pollution.

Organic fertilizers can perfectly replicate the natural recycling of nutrients in the soil. They are a sustainable approach towards building soil health and growing plants.

Winner: Flower Girl Bud and Bloom Booster by Dr. Earth


Bulb Food

Bulbs are the flower buds that appear on your Irises in the blooming season. Your plant requires a regular feeding of fertilizers rich in phosphorus or plant foods designed specifically for feeding bulbs.

A bulb fertilizer or food will not only improve the plant growth but also enhance blooming, so I would highly recommend feeding your Irises with this type of fertilizer in the blooming period.

Before the plant starts blooming, the bulbs will start storing food and energy that will be utilized later.

While planting bulbs, it is highly recommended to feed them with a phosphorus-based fertilizer.

Winner: Bulb-Tone by Espoma


Bone Meal Fertilizer

Your favorite Irises can produce charming blooms only if the roots and stems are strong and healthy. For this reason, a bone meal fertilizer is a top choice for blooming Irises.

Bone meal is made from animal bones and is used by several organic gardeners to add phosphorus to the soil.

Irises need phosphorus because it strengthens plant roots and stems. It also helps the plant in its blooming process.

Adding phosphorus will definitely increase the blooms on your Irises, but make sure the soil pH is not higher than 7. If this happens, do some adjustments to your soil, or the bone meal will not work.

A single application of bone meal can release phosphorus in the soil for about four months.

Winner: Bone Meal All Natural Plant Food by Espoma


Fertilizing Irises

If you have healthy soil, your Iris might not need any significant amount of fertilizers.

But unfortunately, that’s not the case for most of us because no matter how fertile the soil, the nutrients will deplete with time.

Before adding any plant food or fertilizers, I would recommend testing the soil to avoid over or under fertilizing your Irises. This is important because incorrect feeding can result in premature death, and your Iris will die even before it starts growing or blooming.

In terms of macronutrients, make sure the soil is low in nitrogen because that’s the preferred growing environment for Irises.

Most varieties bloom in the early summer months, but some varieties are remontant, so they bloom more than once. 

You should start fertilizing 6-8 weeks before blooming.

Feeding your Irises before the blooming helps them prepare for the coming season. Most growers add fertilizers in early spring.

During the early growth of bulbs, you need a fertilizer rich in phosphorus because it helps in root development and plant growth. 

Phosphate is the most important fertilizer nutrient for this flowering plant variety. But you can also opt for a bone meal or balanced fertilizer.

Phosphorus is also essential because it’s all about root or rhizome development.

The amount of nitrogen varies depending on your soil. Generally, you should avoid fertilizing with a high nitrogen fertilizer because it might suppress blooms, weak foliage, or cause rot issues.

The ideal soil pH for growing Irises is 6.5 to 6.8 as it helps them absorb the nutrients efficiently.

But do not worry much about this because Irises are not demanding in terms of soil pH, and regardless you can easily alter the soil pH using lime or sulfur.

Below are few tips for fertilizing Irises.

  • Spread the fertilizer a few inches away from the root zone because direct contact can burn the rhizome or bulbs. Lightly apply the fertilizer around the clumps.
  • Whether you are growing dwarf Iris, bearded or tall Iris, all of them need to be fertilized one month before their bloom cycle begins.
  • Do not skip fertilizing Irises during planting time. You can sprinkle some fertilizer around the root zone of the potted Iris. For in-ground, Irises spread the fertilizer in the ground bed.
  • Irises do not respond well to overfeeding. Therefore, I always recommend applying less than needed if unsure.
  • Fertilize the plant one month before the blooming and later in September for best blooms and growth.
  • Fertilizing at the end of the blooming cycle will help the Iris stay healthy throughout the year. This extra food will also help them withstand the winter dormancy. Better wait for at least 1 month after the end of the blossoming season.
  • Avoid using high nitrogen manure or composts because that can result in more leaves and fewer flowers.
  • If you prepare the garden bed with fresh compost and fertilizer, your Iris will not need any additional feeding at the time of planting.
  • The fertilizer should be worked properly in the soil because leaving it on the soil surface can result in mold growth. Mixing in the soil will also ensure better distribution of nutrition.
  • Regularly test the soil. If it indicates a lack of phosphorus, spread a handful of bone meal.
  • If you’re using the granular type of fertilizer, apply it to wet soil.
  • Keep the fertilizer away from foliage especially wet leaves. Small granules of fertilizer left on the leaves can burn them.
  • Most growers side dress the Irises with fertilizer in early spring.
  • If your Irises are suffering from phosphorus deficiency, they’ll turn red or purple.



Irises are showstoppers in spring and summer gardens with their ruffled vibrant blooms.

Before choosing any fertilizer, think about your end goal, i.e., what is the purpose of the fertilizer. This helps you select a fertilizer that will fulfill your current requirement.

A simple tip is to choose a fertilizer that is high in potassium and phosphorus but has low nitrogen levels. Focus more on bulb growth because weak bulbs will result in fewer blooms because the plant cannot grow to its fullest.

Test your soil today and buy the best fertilizer for Irises.