For many gardeners, the allure of irises is simply irresistible. Whether you’re a seasoned gardening veteran or just starting out, caring for these rugged beauties can be a rewarding experience. The enchanting flowers make your garden burst with spring color and, if you choose the right cultivars, wonderful fragrance.
At Fragrant Iris, we’re passionate about helping you find truly fragrant irises and sharing our knowledge on how to properly care for them. Let’s dive in and explore the essential steps to ensure your irises thrive in your garden.
Understanding Irises
Named after the Greek goddess of rainbows, irises are beautiful flowering perennials that belong to the Iridaceae family. Through many decades of devoted effort, iris breeders have produced bearded irises in virtually every color, including purple, blue, yellow, pink, white, orange, black, and, one of the most elusive, shades of red. (There is no iris gene for red but dedicated breeders have come incredibly close.)
There are three main types of irises: Bearded, Aril and Beardless.
Arils are gorgeous flowers but are very demanding about growing conditions. They are difficult to grow except in the hottest, driest regions. However, when crossed with bearded cultivars, the resulting ‘Arilbreds’ can be grown right along with the bearded irises.
Beardless irises include Spurias, Siberians, Japanese, Louisiana and Pacific Coast Natives. Cultural requirements for beardless irises vary significantly from the bearded irises, mostly due to higher moisture demands.
For this article, we’re going to focus exclusively on bearded iris culture. (Again, most Arilbred iris can be grown under the same conditions as the beardless varieties.)
Understanding Bearded Irises
The ‘beard’ on bearded irises is a small patch of hairlike structures that appears on the center of each of the falls (the lower petals) and runs back toward the inner part of the flower. It is presumed the beards help lead insects to the pollen-bearing stamens.
Bearded Irises grow from rhizomes. Rhizomes are the thick, fleshy, potato-looking stems that store food and water for the plant. This is what gives the bearded iris its incredible drought tolerance.
There are six ‘types’ of bearded iris. They are, listed by height, Miniature Dwarf Bearded, Standard Dwarf Bearded, Intermediate, Border Bearded, Miniature Tall Bearded and Tall Bearded. That is also the order of their bloom times, beginning with the MDBs and ending with the TBs.
Planting and Caring for Irises
Keep in mind these general guidelines for successful iris planting.
Find the Perfect Location
For reliable blooming, bearded irises require six to eight hours of full sun each day. They will grow in shaded areas but blooms will be reduced or non-existent.
Bearded irises MUST have good drainage. If the rhizome is allowed to sit in standing water for extended periods it will almost certainly develop rot. It’s fine for the soil around the roots to remain moist so long as the rhizome itself dries thoroughly between waterings.
Drainage is usually not a problem in sandy soils but, if your soil has a high clay content, you may want to build raised beds or at least a raised ‘spot’ that keeps the rhizome high enough to avoid becoming waterlogged.
Planting Irises
Soil Preparation: Remember, drainage, drainage, drainage…
Planting Depth: Proper planting depth depends on your soil and climate conditions. If drainage is a concern, keep the rhizome at the soil level and sufficiently elevated to avoid rot. If your area experiences extremely cold winters and/or extremely hot summers, it would be best to plant so the rhizome is covered by an inch or so of soil.
Spacing: Depending on the individual cultivar, a single rhizome can become six to eight rhizomes during its first growing year. Within three to five years most iris clumps will become sufficiently crowded to require lifting and dividing.
You’ll know for certain when the clump produces fewer blooms, an indication of over-crowding. Planting rhizomes at least 18” to 24” apart will allow room for increase. Planting farther apart will extend the growing time before lifting and dividing will be required.
Watering: Newly planted rhizomes should be kept moist, but not too wet, until new roots have had time to become established. This usually requires about ten days to two weeks. After that, keeping the roots (below ground) moist but the rhizome (above ground) dry will produce the best growth. But, once established, bearded irises are very drought tolerant.
Mulching: In all but the hottest climates it’s best not to mulch bearded irises. You usually don’t want anything that might hold moisture around the rhizome. If your soil is subject to wind erosion you might consider using pea-gravel as a ‘dry’ mulch. It will help prevent erosion without risk of rot to the rhizome.
Caring for Irises
After planting your irises, it’s easy to maintain their health with minimal care.
Fertilizing: Fertilizers are listed with three numbers indicating the N-P-K content of the fertilizer. N = Nitrogen, P = Phosphorus and K = Potassium. Nitrogen produces green, leafy growth. Phosphorus is needed for healthy blooms and Potassium helps produce vigorous roots.
Bearded irises should be fertilized twice each year. The first application should be made two to four weeks before blooming. The second application should be made in early fall. Do NOT use a fertilizer with too much nitrogen, such as a 10-10-10 or a 10-5-10.
Too much fertilizer will result in lots of leaves and few if any, blooms. A better choice would be a 6-12-12 or 5-10-5 or something similar, Just be careful not to overdo the nitrogen.
Deadheading: Remove spent blooms to encourage continuous blooming and prevent seed production. This allows your irises to use their energy to produce more blooms and more rhizomes rather than producing seeds.
Dividing: As your irises increase the new rhizomes will eventually become crowded. This will lead to reduced blooms but it also provides the opportunity to expand your iris garden and/or share your bounty with other avid gardeners. It’s best to lift and divide your crowded irises about six weeks after they finish blooming. Bearded irises enter a dormant period about then. Carefully lift each clump, preferably when the soil is moist.
You can break the clump into pieces or you can cut the rhizomes apart with a clean, sharp knife or pruners. Cut the leaves back to around five or six inches tall. (This helps prevent wind from rocking the newly planted rhizomes out of the ground.)
I like to pin down the new rhizomes with a lawn staple, also known as a landscaping staple. I just leave the staple in place as it won’t harm the iris plant.
Pest and Disease Management: For the most part, the only real insect pest you need to be concerned with is the iris borer. They can be difficult to control as the tiny borers will ‘bore’ into the leaf soon after hatching, then continue to feed inside the leaf, eventually working their way down to the rhizome before emerging as adults to mate and lay eggs on the iris leaves in the fall.
Nematodes can be applied in spring and fall for a ‘natural’ control. If you notice ‘swollen’ areas on the leaves it could be a borer working inside the leaf. It’s best to remove the affected leaves and dispose of them. Do NOT add iris leaves to your compost as the borers could easily survive.
Finding Fragrant Iris Cultivars
Not all bearded iris varieties are fragrant. There are around 85,000 named varieties of bearded iris (possibly more). Of those, only a small percentage possess a truly rich fragrance. Many are only slightly fragrant.
I’ve made it my mission to identify the most fragrant iris cultivars, locate sources for those that are still available (many, unfortunately, have become extinct), then acquire a few rhizomes and grow them to a sufficient quantity to offer them for sale on my website, www.FragrantIris.com.
I have a very long list of fragrant cultivars that are either no longer available or are very, very difficult to locate and acquire.
If you happen to grow bearded irises, have one or more extremely fragrant cultivars and are certain of the name, I’m always in the market for any variety I do not currently have in my inventory. Feel free to contact me if you would be interested in selling a few rhizomes.
Enjoy the Fruits of Your Labor
Finally, take the time to appreciate the beauty and fragrance of your irises as they grace your garden. Whether you’re admiring their intricate blooms up close or cutting a few stems to bring indoors, irises never fail to delight the senses. With proper care, your irises will continue to thrive and bring joy year after year.
Grow Your Garden With Fragrant Iris
Whether you need a fragrant iris rhizome to add to your collection or are looking for tips on caring for them, Fragrant Iris is here to help. We specialize in fragrant irises that smell as good as they look, the perfect addition to any garden.
Contact us today and experience the beauty of fragrant irises.