Knowledge from Olle Garden Bed: 6 Reasons Why Your Iris Did Not Bloom

I don't think I've ever seen anyone really buy iris flowers and plant them in their garden, just like roses or azaleas. The following content also has some reference value for raised garden beds.

Think about it. Every Iris grower I ever talked to owns their Iris (sometimes even the entire collection) from others' generosity - either from generation to generation, from one neighbor to another, or from one homeowner to the next.

If you have also planted iris flowers, you will notice that once the plants settle down in your space, they will soon become the real main landscape.

As a long-lived perennial plant, Iris flowers reliably year after year without too much trouble and trouble. They come in a variety of colors and hues (purple, yellow, peach, pink, magenta, blue, white, and different two-color combinations), ranging in size from a 10 inch tall dwarf iris to a five foot tall bearded yellow iris.

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Generally speaking, Iris will appear as early as April (usually in warm climate), but some varieties will start flowering in June. This flowering period varies according to your gardening area and microclimate, but it is certain that for most people in the Northern Hemisphere, iris is a flower in early summer.

Therefore, when your iris suddenly fails to bloom, it is even more disappointing. Or, more commonly, you can only get a few flowers from the big iris patches.

There are several common reasons (and many less common reasons) why iris does not bloom. But each of these problems also has a solution, so through some troubleshooting and greater patience, you will let your iris bloom again next year.

In this guide, we will discuss rhizomatous iris, such as bearded iris and Siberian iris, because these are the most popular flowers for gardeners. These are also iris flowers that grow in soil, not in water (such as Japanese iris), so please remember this when troubleshooting.

Let's take a look at the main reasons why your iris does not bloom:

  1. Your iris is too crowded.

Let's start with the most common reason why iris flowers don't grow stems - they become too crowded. There is a simple solution to this problem: you can divide your iris into several lumps and replant them.

If you want to prevent the disappointment of overcrowded plants, you should default to dividing the iris every three to four years. If you are gardening in a cool climate, you can have a longer interval between partitions. But if you are in a warm and humid climate, your iris will surely grow faster, and you may need to partition more frequently.

If you are going to replant newly split rhizomes, let's continue to discuss the next point in the list to ensure that you maximize their chances of blooming in the future.

  1. Your iris is too deep.

Hopefully dividing your iris will encourage new flowers. But there is a secret to planting iris, which may be counterintuitive, especially if you are used to planting spring bulb gardens.

The second most common reason iris flowers fail to bloom is because they are buried too deep.

Unlike the bulb spring, the rhizome of iris should be horizontally planted in shallow holes. You want the roots to be still underground, but the roots should stick out of the soil. Do not bury the bottom of the rhizome in more than a few inches of soil. Usually only one inch of soil is enough, depending on the thickness of the rhizome. This arrangement allows the air to circulate around the rhizome and to keep the structure dry in the sun in wet weather.

If you want to create a larger patch, you can plant the three root groups together for a fuller look. However, remember to give them some breathing space and keep the group about 12 to 20 inches away. As a general rule, the higher the variety of iris you plant, the farther you can spread it. Don't worry, they will continue to grow. You must repeat the division process every three years.

Avoid replanting iris flowers where diseased rhizomes are found.

Keep the newly transplanted rhizomes well watered, several times a week, until you begin to notice the new growth. Do not directly water the protruding rhizomes, but keep the surrounding soil moist.

Iris is one of the few best plants not covered in our garden, because the mulch may cause the root rot, especially if your website has poor drainage or does not have enough sunshine time (see below for more information).

The young rhizomes you have just planted, especially those that have been cut down, need at least one year to rebuild and grow enough to bloom.

If you have moved to a place where there are irises, but you can't see the rhizome sticking out horizontally from the soil, you still need to dig them out and replant them in a shallower depth.

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  1. Your iris needs more sunlight.

You can plant dense iris leaves in the shade, but don't expect too many flowers.

In order to flower, the iris should get at least six to eight hours of full sunlight. In extremely hot weather, they need some afternoon mottled shade to prevent them from being burnt. But as a general rule, the more sunshine they get, the better.

That's why you should try to plant your iris in an open place. When you first select their location, you may have already done so, but over time, other trees, shrubs or man-made structures around you may have begun to cast shadows on your iris.

Iris does not like to compete with stronger plants or trees around, whether in light or water demand, so pairing them with plants with the same requirements (such as Hemerocallis fulva) is the best choice to keep them happy.

If you are not sure how much sunshine your iris has, please choose a sunny day from mid spring to early summer. Start in the morning. If the sunshine reaches the place where iris is planted, record it every hour.

The simplest way to solve this problem, but perhaps not the simplest, is to relocate the iris to the area exposed to sunlight for as much time as possible.

  1. Your iris doesn't get enough water.

I've seen iris appear on several dryland gardening lists. If you are not familiar with the term, it refers to a horticultural philosophy that encourages the use of drought tolerant plants in dry climates. This is a more modest way of gardening, both in terms of water saving and gardener costs.

So, if you can use iris in drying, what benefits will it have? How can drought tolerant plants lack water? Well, the plants themselves can deal with a lot of stress caused by lack of water. But one of the main ways to save energy is not to put flowers.

Not only should you water the iris grafts to help them build up, but if you don't have enough rain in late winter and early spring, you should also water them twice a week. This is the time when the iris wakes up from its dormancy and starts to release its flower stems.

It is worth reminding that too much water is as harmful to plants as too little water, because too much water will lead to root rot and even leaf spot disease. Water the iris only if there is not enough rain and the top three inches of soil is dry. You can reduce the watering frequency at the end of autumn and throughout winter.

When you water the iris flower, don't pour it directly on the root and try not to wet the leaves. Pour water around the roots to prevent moisture from accumulating around them and to keep it permanently moist.

  1. Your iris absorbs too much nitrogen.

Like most blooming plants, the iris fed with too much nitrogen will use it to grow richer leaves at the expense of flowering. Therefore, it is a balanced behavior to apply fertilizer to iris. It is necessary to add sufficient phosphorus to promote flowering, but not excessive nitrogen (to promote leaf growth).

Sometimes, the iris growing in or around the lawn lacks flowering. Even though you may not have fertilized the iris, if you have used lawn fertilizer, you may have added too much nitrogen to the soil.

Only when you plant iris flowers in the same place for a long time, do you really need to fertilize them. The area has been depleted and needs some soil amendments, especially phosphorus. If you are not sure whether your soil is still good enough, soil testing is the best way to determine soil needs.

If you decide to apply fertilizer, we suggest you use low nitrogen organic slow release fertilizer, such as 6-10-10 mixture or 5-10-5 mixture. You can fertilize the iris once before flowering in spring and again after flowering.

When you fertilize plants, do not apply feed directly to the roots. You can soak the soil around the roots with liquid feed or use slow release granules. When feeding plants, be sure to follow the instructions on the package, and use less fertilizer than indicated on the bottle by mistake, and feed less frequently.

However, a better way to ensure a balanced diet of plants is to modify the planting site with organic compost when cutting and transplanting iris flowers.

Like most flowering plants, irises thrive in well drained soil. If the soil is too compacted, the water will not be drained, making the roots wet, which may cause decay. If you need to make the soil looser and more absorbent, you can add compost or leaf mold.

However, if you want to add feces, please be careful, because some feces that are not old enough may contain too much nitrogen to your iris.

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  1. You cut off the iris leaves prematurely.

I left this reason on my list because it is unlikely to happen. But if so, you will know why.

Some people are used to cutting the iris leaves into a fan shape after flowering in the season. Gardeners do this mainly for aesthetic reasons, because they believe that the iris can better integrate into their landscape. But I think this is a misleading habit. The only time you want to cut the leaves is if you are dividing your plant, as we described above.

This is because plants need leaves to remain attached as long as possible to absorb sunlight, which is urgently needed for photosynthesis. This helps the rhizome store energy for next year's flowering. If you cut the leaves too early, the shrinking of the leaves may affect the flowering of the next season.

I suspect that this suggestion was initially spread mainly by growers and hybrids. There are hundreds of plants to take care of, and cutting leaves makes tasks easier to manage. In their case, they want the plant's energy to be used to strengthen the rhizome (which they will sell), and they don't care much about flowering.

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If you still want to trim the leaves, please wait at least two months after the flowers fade (or calculate from the time when they should fade, if you do not bloom this year).

These are the main reasons why iris will not blossom during flowering. For Iris and most of the plants we plant in the garden, the name of the game is Patience.