Best Time to Fertilize Irises [Early Spring & Late Summer]

Have you ever wondered why or when you should fertilize your iris? With all these wonderful things that can happen if you can grow them well, the best and easiest thing to do is to feed them properly. If you can remember the start of your garden, you will know that it took a lot of effort, time, and effort to prepare it for the busy season. Now you want to make it bloom and enjoy the fruits of your work.

There is nothing wrong with taking care of your garden because as time passes, you know that there are seasons that come around, especially in spring and summer. There are times when so many things are happening all at once, from the buds starting to open on the flowers of plants to the arrival of the butterflies.

For us, this means we need to take care of our plants and make sure they can grow well so they can bloom right before those other busy times. This article will show you the Best time to Fertilize Irises. 

How to know if you should apply fertilizer?

You can always perform soil tests through your local extension office. They will help you send samples off the lab for analysis and mail you the results. Here you can purchase easy-to-use kits for lawns and gardens.

If you are wondering how to know if you should fertilize, it is pretty simple.

1. Yellow leaves

You are likely suffering from a nitrogen or potassium deficiency. You can check to see if you lack any of these nutrients by adding a small fertilizer to your soil. If the leaf changes color, then you know that you need some nitrogen.

2. Potted plants or bud breakage

If your plant or flower is dying or breaking off, it may suffer from low potassium in the soil. You can check to see if you are deficient by applying a fertilizer with high potassium levels.

3. Lack of green growth

If you have a lack of green growth in your plant, you may be lacking enough nitrogen. To check this, you can add a little nitrogen fertilizer to the soil and see if it grows back to green. If it doesn’t, you know there is a nitrogen deficiency.

4. Black or dead spots in leaves

This means that your plant lacks nitrogen or phosphorus. You can add fertilizer for each nutrient and see if the plant grows healthy. If the spots don’t return in a week, there is a nitrogen deficiency.

5. Leaves curling up or dying

This is a low-nitrogen problem; you can check for it by applying fertilizer with high nitrogen levels. You can also take a leaf and place it in a water jar with a high-nitrogen fertilizer. If the leaf sags or wilts, then there might be a nitrogen deficiency in that leaf. The same method can be used to check if your plant has phosphorus by dipping the stem into kitty litter and watering it first, then checking to see if it comes back green again.

6. Red or Purple discoloration on leaves

If your plant has discolored leaves and a phosphorus deficiency, you can check for it by watering it with a half-strength fertilizer with various levels of phosphorus. You want to check the red or purple coloration on the leaves for two days until you see some new green underneath. If the spots don’t return in two days, there is a phosphorus deficiency, and you need to add more.

7.No flowers or poor performance

You will know if this is the case by checking the plant’s blooming pattern. If it is not blooming at all, then this means there is a low nitrogen problem. You can do the same thing in step 5 to check for a deficiency of another nutrient.

What fertilizer to apply?

There are many factors to consider when choosing the right fertilizer for your plants. Some of these include sunlight intensity and location, pH, whether it is a plant that requires direct sunlight or not, whether it is in a container or not, whether you live in an area that has cold winters and many hours of sunshine per day, what kind of soil and nutrients the soil has available to support your particular plant’s needs, and also how much fertilizer you want to put on initially.

Calcium can be added to adjust the pH of the soil if it is acidic. Calcium helps soil alkaline by enhancing soil acidity. Bones from animals are processed to create the bone meal. This fertilizer is recommended to add calcium to garden beds. Add an amount based on how much of the soil needs acidifying.

The general guideline is 2 pounds of bone meal for every 100 square feet of garden space, so 1 pound for every 10-12 square feet and 2 pounds for every 20 to 30 square feet.

How to apply fertilizer?

Follow the directions on the label of the container you intend to use to fertilize your plants. There are a variety of options when it comes to applying fertilizer. Liquid, granular and granular pellets are common types of fertilizers. Mixing particles can vary depending on the fertilizer you use and the goal of preparing the soil for your plants. Different fertilizers are available, including soluble, slow-release, granular, and organic fertilizers.

Benefits of Fertilizing Irises

  • There are many benefits of fertilizing irises, provided you choose the correct type of fertilizer at the correct amount and with the appropriate instructions. The most significant benefit is an increase in flower production. Using a correct and adequate amount of fertilizer can increase the number of flowers on each plant by approximately 25%. Fertilizer helps to fill in weak spots or areas that may have been weakened by drought or other environmental factors.
  • Adding fertilizer to the soil also aids in maintaining soil quality. Another benefit is that fertilizing helps fight disease and insects in your garden. It stimulates nutrient uptake by plants, encouraging them to remain healthy and strong.
  • Fertilizers also improve nitrogen uptake from the air, which helps plants retain their essential nutrients. The bottom line regarding fertilizer is that it helps take care of your plants so they will bloom better and provide you with beautiful flowers all spring.
  • There are many different fertilizers, and you must select the right one. Most fertilizers contain nutrients such as phosphorus, nitrogen, and potassium that plants need to grow. The amount of nutrients varies depending on soil type, temperature, and available sunlight.
  • Most plants need potassium during their life cycle, so adding potassium to fertilizer can help provide that in a more helpful form. Potassium is especially important when growing irises since they rely on potassium for energy production in their flowers.

Iris Planting Tips for Beginners


Irises should be given space to spread out over time. This helps prevent disease.


Make sure your soil is fine and not too heavy. Mixing in some compost and worm castings will help a great deal.


Irrigate regularly, especially during the last week when you are tillering. The first few weeks will be less critical, but once your plants have been well established, they require little or no special attention.


Use a fertilizer with lower phosphate content to ensure new growth doesn’t look too yellow in the spring. The earlier you start feeding, the better. Use several different types of bloom with different timing for best results and one for later in the season for additional color and to provide nitrogen for flowering.

Please don’t go overboard on fertilizer since it can cause root burn, particularly on cool nights, which may lead to stunted growth or even dieback of the iris plant’s foliage and flower stems.


This is very important to encourage healthy, bushy growth. Avoid severe pruning unless you need to. I have been told that if you cut off the foliage right at the base of the plant, it will not affect flowering. Also, remember that they will need less water as they mature, so make sure you don’t give them too much.

Keep a close eye on your plants once they bloom, and check to see if you need to cut and remove old leaves. If too many canes exist, cut them off to force new growth.


Normal room temperature tends to be the best for flowering because cool temperatures promote flower bud production. Iris plants will grow and bloom more vigorously in cool temperatures than in higher temperatures.


 The best light is full sun, but they will also survive in partial shade.


Mulch helps to retain moisture and prevent soil from drying out. The soil will have better drainage, which will create less root rot. Also, plant your Iris in a well-drained area with good drainage, so the roots don’t get trapped and die.

Iris flowers are highly attractive to butterflies and birds, especially hummingbirds. On the other hand, the monarch butterfly’s eggs are poisonous to humans and animals.

Recommended varieties

German irises, Iris germanica, come in many different colors. Some are blooming during the fall. Rebloomers (remontant) varieties include:

  • Jennifer Rebecca
  • Immortality
  • Earl of Essex
  • ‘Feed Back


In this article, I discussed some things you need to consider when growing your flowers. I also explained different types of iris, different types of soil, and how to plant them for the best results. Finally, I will conclude with what Iris species are typically grown. It is important to check with the iris breeder or seed supplier to whom you are purchasing your seeds to ensure you are getting the right species for your area. I hope this article has helped you in your future flower garden. If you have any questions, ask me in the comment section.