The Iris (EYE-ris) genus isn’t the largest out there, having somewhere between 260 and 300 species, but it is a pretty complex one.
With six subgenera and many of those being further divided, it can get a little complicated to discuss caring for irises in general.
However, one thing all irises have in common is that you can grow them in containers, despite this being something of a gardening secret. In general, bearded irises do better in pots than other varieties.
Because there are a few special rules regarding the care of potted irises, this option might not seem at first to be feasible.
However, once you know the basics, growing potted irises can be pretty rewarding, and some irises can even bloom out of season as a result!
Potted Iris: How To Care For And Grow Potted Iris Plants?
A little extra care is needed to provide the appropriate amounts of sun, food, and water for a potted iris.
Additionally, winter care is slightly different, as is the frequency it might need to divide the plant.
Know Your Iris!
Before getting started, it cannot be stressed enough that you need to understand the primary care needs of a particular iris before attempting to pot it.
Some species, such as the yellow flag (Iris pseudacorus), prefer wetter soil conditions, while many hate soggy soil.
Some irises will need more light than others, and some need more prosperous soil conditions.
By knowing any special needs, your iris plant has, you can adjust the following information slightly to better suit those needs.
For example, an iris that needs very little water can be allowed to dry to a deeper depth, while the aforementioned yellow flag iris will need to be watered when the surface is dry.
Choosing A Pot
Unlike many more commonly potted plants, your choice for an iris requires some planning ahead.
This is because most irises don’t like to be disturbed, so the less often you need to repot, the better.
Tall bearded iris will need a sufficiently large container; no less than 12″ inches in diameter is recommended.
Meanwhile, dwarf iris varieties, such as the reticulated iris (Iris reticulata), will need a pot around 6″ to 8″ inches in diameter.
A good rule of thumb is to consider how wide your iris will likely be once it clumps and choose a pot about the same size.
This will prevent the plant from becoming rootbound before it’s time to divide it.
Ensure the pot is well-draining, as water is more restricted in a container than the ground.
Ceramic or terra cotta pots can help prevent water retention while providing a little extra insulation in winter.
However, just about any decent material will work, and it’s not uncommon for growers to use large plastic pots or metal tubs with drainage holes to plant multiple irises together.
While it’s easy enough to make iris potting soil based on the needs of a particular plant, the general rule is for the ground to have a pH of 6.5 to 6.8, with the latter being ideal.
To increase acidity, add a little peat moss a few months prior.
However, it’s usually best to purchase rich soil with good drainage organic potting mix with the appropriate acidity. Add in some perlite to further improve drainage.
Mix in a little extra organic compost for irises that need richer soil, while irises better suited for poor soils can often use a less rich mix with a bit of coarse sand mixed in.
When preparing a pot, consider how much water the plant likes.
For those who need superior drainage, consider putting a base layer of gravel in the bottom of the pot to create a buffer zone while the water drains.
A Note On Planting
While it’s possible to plant more than one iris in a pot, it’s usually best to give each their separate pot. It’s especially true of rhizomatous irises, as they tend to spread out horizontally.
For bulbous irises, you’ll need to space each plant at least 6″ inches apart, although you shouldn’t plant more than three bulbs per container.
You can thin the young plants out or start them in a nursery container before planting them into their permanent pots when growing from seed.
Plant rhizomes so that the very top is above soil level, as they need exposure to the elements to thrive. Bulbs should be planted in a hole three times their height.
Lighting And Hours Of Sunlight
Because irises don’t like being moved around, find a spot where they can get enough sunlight all year round or supplement natural light with grow lamps.
Most irises will need 6 to 8 hours of full sun per day.
If overwintering your iris, it will prefer a dark room, but if you’re planning to force blooms, it will need good lighting throughout the winter.
A window with unobstructed southern exposure is perhaps the best choice.
In some cases, growers prefer to place their containers outdoors during the warmer months and overwinter them inside to ensure the best possible lighting.
The soak-and-dry method is essential for a potted plant because the water takes longer to drain out.
Water the soil dry 1″ to 2″ inches deep for most irises, but water when the surface is dry for species that prefer wetlands.
A balanced liquid houseplant fertilizer will work wonders for your potted iris. Depending on the individual plant, it may need to adjust how much and how often it is fed.
Yellow flags and similar species often don’t require feeding at least once at the beginning of the growing season. In the fall, add some bone meal to the potting soil.
Pay Attention To Winter Needs
Depending on the species, irises may be winter bloomers or die back for the winter.
Consider the winter care requirements for when your plant’s in a garden and adopt those rules for the potted plant.
If a plant can be forced or have a winter bloomer, take advantage of the flexible indoor climate to provide the needed light and temperatures.
Note that bulbous irises can be protected with a layer of mulch, but rhizomatous irises may become diseased if wholly covered.
When To Repot
At last, we come to a more-or-less universal aspect.
Repot your iris every 3 to 5 years, using that time to divide the rhizomes or bulbs and replace the soil.
Be sure to plant rhizomes to the same depth as they were before transplanting.