Although you would think such elegant-looking flowers would be difficult to grow, the iris family requires very little maintenance. These long-lived, hardy perennials can grow in a variety of soils providing it drains well and they can flourish in full sun to partial shade. However, just because they’re easy to grow does not mean that they’re without their share of problems.
1. Winter Rot (Botrytis)
The sooner you identify the signs of winter rot, the faster you can remove the affected plants from your garden so others aren’t compromised. There is not a lot known about this fungus other than its destructive and is typically seen during the freezing and thawing periods associated with spring.
This corky, dry rot will often leave the rhizome practically weightless. You can identify it by black sclerotia that resemble a brain, measuring about half an inch wide.
Generally removing the affected rhizomes is enough to remedy the problem, side shoots and new growth will often be free of infection. The easiest way to avoid winter rot is to mulch heavily in cold climates.
2. Mustard Seed Fungus
Sclerotium rolfsii is the pathogen that is commonly referred to as mustard seed fungus. It receives this name because it presents itself as spherical and brown, similar to the color and size of mustard seeds. Depending on geography, some also know this iris problem as crown rot or southern blight. It is soil-borne and just waits patiently for you to plant an iris so it can attack.
Mustard seed fungus doesn’t usually show up until later in the spring or the beginning of summer when the fans are starting to expire. When you inspect the plant, you will notice that the rhizomes appear to be scale-like, crusty and the roots will look like a mass of threads. Around the plant, in the ground is where you’ll see these seeds scattered.
This problem can be controlled by offering sanitary growing conditions, exposing the rhizomes to direct sunlight, cleaning the infected tissue and dipping in a 10 percent bleach solution before transplanting.
3. Leaf Spot
This is a fungus that overwinters on dead remains of the iris such as leaves that have not been cleaned away. The affected leaves will first look like they have wet spots which later turn brown and often multiply, killing the infected leaves.
Humid, foggy or wet conditions are often to blame for leaf spot but it is an iris problem that can be addressed. Remove the leaves immediately and provide the plant with good air circulation.
Always avoid transplanting irises in wet weather because you can spread the disease. It is also important to note that leaf spot does not permanently affect the plant’s rhizome. It does generally offer a two-year cycle and will have an adverse effect on blooming the following year but the plant should be fine the year after.
4. Bacterial Soft Rot
Of all iris problems, this one is most common and easy to recognize due to the foul odor that it offers. Bacterial soft rot can spread to and destroy nearby plants so it is imperative that you catch the problem in its early stages. Overwatering and too much fertilizer are common causes which is why it usually makes it presence known in the spring.
To treat an infected plant, all you need to do is use a sharp knife to scrape the mushy part off the rhizome. Once this is done, clean the area with a 9:1 ratio of water to bleach and then dust with sulfur. Avoid watering the plant until symptoms disappear. Making sure that you plant your iris in well-drained soil will reduce the risk of bacterial soft rot.
5. Scorch
Most commonly seen in the southern states, the exact cause of scorch is undetermined and prevention is up for debate. The center of the leaves get very dry and begin dying at the tips. Leaves fade to brown; the roots die after rotting yet the rhizome often remain firm.
Some plants can be saved by digging them up, drying them in the sun and replanting but you won’t really know until the following season if your efforts have been successful.
Want to learn more about common iris problems?
See these websties:
Iris Diseases by Penn State Extension
Bearded Iris for the Home Landscape by North Carolina Cooperative Extension
I planted my bearded iris last fall, some of them are blooming now and are beautiful however about four of them are blooming so close to the ground bottom peeled are laying on the ground, what is wrong
I am having the same problem! I don’t know why, but nice to know I’m not the only one having this difficulty! Makes me mad, the flowers are so so pretty!
I purchased my iris a year ago when it was blooming. It was in a very small plastic pot so I replanted it in a large clay pot. It sent up two more beautiful blooms. I cut the leaves back in the fall. This year the leaves came up beautifully but no flowers. The leaves are beginning to turn yellow so I cut them back. The rhizomes seem very strong and solid. What is wrong ???
My bearded iris bud but then the bloom doesn’t open and it rots
What is wrong?
Mine too! What should I do?
Hello! It needs more room to grow. 🙂 Iris grows to the side. They will not bloom if they are over crowded. 🙂
Several things could be going on– I know, this is 5 years old and hopefully your iris is set straight! Irises are actually pretty easy to care for and grow. They really need very little, just a watchful eye to check for pests like iris borers, snails and the like, only modest watering as they’re pretty drought tough, and adequate sunlight. They can take a regular balanced fertilizer once a month in the off-season and a bloom fertilizer with some bone meal as the bloom season approaches– beginning about 6-8 weeks before the season. Nothing outlandish, just regular garden shop stuff is fine. Even “tomato food” works well for irises, as all that does is help plants to make flowers (and ultimately, flowers become “fruit”, whatever THAT may be!). If you grow tomatoes, you can share that tomato food with your flowers!
But irises do need room to grow and increase from the previous rhizome. If they’re crowded, they often slow down the blooming, and can stop altogether until they’re divided.
To do that, you dig up the clump and separate the larger rhizomes from the group. The “mother rhizome” is one that has already bloomed. It will not bloom again itself, but it will produce “toes”, or new shoots which become rhizomes with their own plants and developing stalks. If the “toes” or increases also have a good rhizome, those can be split off from the mother and planted. They may need a year or two to come to size before they bloom, so be patient! The first year, the irises sleep and build up energy. The second year, they creep and begin to produce a few flowers, and increase in size. The third year they leap, and you should have a nice display. Then, they may be ready to divide again! Leave about 18″ or more between new plantings to allow room for new growth. They will “mass plant” in due time all by themselves!
When you replant them, don’t plant or mulch them too deep. The rhizome should be right at the surface of the soil. The rhizome itself is actually a specialized part of the stem, and needs to get some sunlight. It should be like a duck, just “floating” with its back at the soil level and its roots down in the soil. When I plant iris rhizomes, I dig a hole just deep enough for the roots to hang down, then I make a little mound of soil in the hole as a “perch” for the rhizome to sit on, and then fill in the root holes so that the rhizome is level or just EVER SO SLIGHTLY covered with a thin layer of soil, and then press the soil comfortably around the roots. I don’t always cut the leaves back when I plant, unless they’re very large and heavy. The leaves help to feed the newly planted iris, so I don’t like to take much of that away if I can help it. Smaller leaves, I leave those alone but ones with VERY large, tall leaves I may trim just a little bit. The leaves will refresh and old leaves will eventually shed.
Next, if you feed a fertilizer with high amounts of nitrogen, this will give lots of leaves, but not a lot of blooms. This can also lead to rotting. Roll back the nitrogen and feed a fertilizer that promotes blooming. Higher second number in the “3 numbers” (NPK), and some bone meal is helpful.
Make sure that they get at least 6-7 hours of sunlight per day. You can give them a mid-day break if you live in a hot climate, as long as the total amount of sunlight is at least 6 to 8 hours.
Do not overwater your irises. They really only need about an inch of rain or hose watering per week. Bearded irises aren’t like Louisiana or Japanese irises that do need more water. They’re pretty drought tolerant, so just give them an inch or two of watering per week if you don’t get natural rain. Too much water can lead to rot.
If you get pods on your irises, you can do a couple of things. You can leave the pods to dry on their own and collect the seeds to try to grow new irises. They will NOT be true to their parent plants, but you might end up with some really neat new colors or patterns as a result of the genetics, even if the pod is self-set. Or, you can just cut the pods off and throw them away. These are bee pods. They happen when a bee or some other critter gets in there and pollinates the flower. Irises can be hand pollinated pretty easily, which is why there are so many different colors, shapes, etc. in those tempting iris catalogs!
Fantastic information and pleasantly written! Thanks!
Our iris bloom but then the petals with collapse and gum up. Otherwise they are healthy and beautiful
Iris flowers only last a few days for each blossom here in upstate NY. Some varieties’ flowers last a bit longer than others, but what you are describing sounds like the normal evolution of an iris flower. Once the petals shrivel into a wet glob I snap them off, being careful not to snap the second bud that often shares its papery bud sheath. I’ve found that removing that spent bud keeps the second one from being spoiled a bit by the sticky wetness of the finished flower. A single flower stalk will usually have 6-8 flowers which usually bloom in succession (again, depends on the variety), so the plant as a whole flowers for 2-3 weeks.
Some iris spathes (the “sheath”) are fleshy, and some are papery. This will depend on the cultivar and the ancestral cultivars or species that went into the making of your particular iris. Some bearded iris have Iris pallida heritage, which sometimes gives a silvery sort of paper-like spathe. Many of the pink irises do have I. pallida in their make-up. In fact, I have a pallida hybrid that has some slight variegation on the bud leaves, which are sickle-shaped rather than straight, and a silvery white papery spathe. The flowers are smaller and distinct from any other type in my gardens. Iris cengialti also produces a smaller, differently-formed bloom from the typical garden irises (which themselves have been so heavily hybridized as to no longer closely resemble their ancestors!)… this one has a brown papery spathe rather than the silver-white of the pallida types and a different chromosome count, as I recall. I. mesopotamica also produces brown papery spathes and has been widely used in the early development of our modern bearded iris. This trait still lingers in some modern irises. Other irises of the “bearded Iris germanica type which is what most of us are probably growing have a green fleshy spathe with very little paper texture, owing to their other ancestral strains. In healthy irises, all of these variations are normal genetic traits and can sometimes help you distinguish one cultivar from another that looks similar… along with other identifying features such as bloom times, bud counts, the absence or presence of purple based foliage, plant heights, etc. I have some irises that rebloom, giving 2 distinct shows at different times of the year. Some of my irises produce an insane number of buds and blooms, with one of my antiques that can produce as many as 14 blooms on a single stalk that branches. Each bloom lasts just a few days, but another one will pop open soon. I pull off spent blooms to keep my irises looking neat and pretty, unless I used that bloom as part of a cross-pollination, and give room for each new bud to open nicely. With as many irises as I have, it’s a task that I do each morning and evening! I’m also a backyard breeder, creating my own unique varieties (since I’m pretty broke and if I had my way and an unlimited budget, I’d buy just far too many from the good folks at Schreiner’s, I’d have absolutely no backyard left, and my neighbors would be pestering me even more for photo ops!)
I planted iris bulbs last year but haven’t even seen any growth . I was wondering what may have caused this. I am so use to them growing like crazy at my last place but nothing here?
my iris turns black at the base and then falls over (rots). i looked for images on the internet to find solution and none of the sick images look like my problem. any idea?
probably should have mentioned i am in SFLA
I also live in South Florida
I’m having same issue and I’m also in S Florida. Did you find a solution?
It seem the stalks of my iris are getting taller and the blooms are getting smaller.
vwsklark, I also live in South Florida and purchased nine Blue walking irises in March. Five are in the ground and I am having the exact same problem you are. The flowers are so beautiful then, all of a sudden the leaves/swords are just laying flat on the ground with that nasty black at the base.
Should I use the same fungicide that I use on my orchids?
I have been reading about iris borers, caterpillar of a moth. The articles I have read say that they bore down in the leaves and into the rhizome and they rot around the base. Investigate those and see if that is the problem.
I bought some Irises about a month ago at Lowe’s. I’m pretty sure it is not blooming season for them but my leaves are turning brown. I am in South Carolina so they are in sun all day but do get watered daily from a sprinkler and drip system. Our soil is also pretty much clay in the area as well surrounded by mulch. Any suggestions are greatly appreciated.
BEARDED irises are rather drought tolerant and can do well with about one inch of water/rain per week. You are describing one of 2 main issues: too much intense sun, or too much water. I’m presuming that you have bearded irises… there are many other kinds of irises that have different needs. Irises like lots of sun– at least 6 -7 hours a day, but it doesn’t have to be all in one long spell. You can give 4 hours in the morning, then a break for a couple of hours in light shade or filtered sun during the hottest part of the day, then 2-4 more hours in the later afternoon or evening. Try rolling the water back as well, to only one or two deep watering sessions per week for an inch or so each time when they’re not blooming. Bearded iris rhizomes do not like to be soggy, or else they can rot. I grow bearded irises in Texas “black clay” soil that also has a lot of limestone, and they’re flourishing. My garden is a party right now (mid-late April is our prime season!) Iris leaves also do die back in succession, but you should see fresh leaves also appearing. During late winter here, we begin to see new increases (new plantlets that shoot off the old rhizome to form new rhizomes and blooming stalks). The original rhizome will not bloom again. New blooms come from the increases. These clusters will eventually need to be dug up and separated, or they will eventually crowd themselves out, which causes reduced blooming. You can replant the divisions, and give any surplus away to friends, or plant them elsewhere in the garden. You can discard old “mother” rhizomes, or use them as a support for your divisions. I have found that some cultivars (“strains”) of bearded irises are very vigorous and increase very rapidly, while others are slow to increase if they do at all. I don’t have time or space for “non-doers” so I either pitch them, or give them to someone else. Sometimes, a non-doer in my garden turns into a thriver 3 yards over. I’ve also received irises that struggled in someone else’s garden that grew to be a show-stopper in mine. Who knows why this is, it can be any number of things but I’ve seen it happen more than once.
My irises are blooming beautifully but will not stay upright. I have to steak all the blooms, even the thick original ones. There are a few growing close to the ground so I am thinking overcrowding? Although they were divided 2 years ago and have space to grow. No rot or pests, watering/ fertilizer is fine. In Southern Ontario.
Thx
It’s April and iris plants look healthy; all except one. It’s leaves looks like it has been frozen in patches, not all over but in patches. Can’t find a solution by googling.
5/15/2023 – We had a lot of rain this winter. The iris is in full sun most of the day and has mulch around it. This is its 2nd year. The tuber multiplied and we now have a few plants that could be divided. It bloomed beautifully – nice big flowers – and many on each stem. My problem is with the iris leaves or blades. Some of them look wrinkled as though it was a piece of material you put down flat and with both hands pushed the edges towards the middle! HELP! Please and thank you! Have a beautiful day!