How (and Why) to Grow Iris from Seed
Nov 20, 2018
Have you ever dreamed of raising your own iris plants from seed? OK, maybe not as much as you've fantasized about going back in time to 1980, dressing up in cheesy clothes, and starring in this music video.
We can't (won't, actually) help you with your wardrobe and classic rock obsessions, but we can help you learn about the diverse iris plant family, and why home hobbyists and budding nursery growers shouldn't be intimidated by starting their irises from scratch.
Iris's Botanical Origins: Rockin' It Old-School
The Iridaceae family, according to Tom Waters of the American Iris Society, likely diverged from other flora into its recognizable form about 82 million years ago...in what we now call Antarctica.
No foolin'. Antarctica.
Back then, the continent was a scooch closer to Africa and connected to Australia...but still somewhat overlapping the Antarctic Circle. Things were much warmer back then, though, and as Waters describes:
It is thought that the strappy, vertical leaves (a distinguishing feature of the iris family) evolved to make maximum use of the sunlight, which would have been nearly horizontal much of the time.
The iris family's relative geographic isolation, and being on the opposite side of the globe 66 million years ago, likely shielded it from the most brutal effects of that enormous, dinosaur-slaying meteorite that splashed down in the Gulf of Mexico. "Although it is estimated that more than half of North America's land plant species were lost in the extinction, few if any species were lost 'down under,' although the numbers of individual plants plummeted," wrote Waters. Yet the Iridaceae survived, bringing us 2000 species, including crocus, daffodils, gladiolus, and other top garden hits.
Given that a plant's origins are more meaningful when discussed within the context of modern geography, we'll call the iris family originally native to Australia and South Africa, though most of the 280-ish species in the Iris genus are indigenous to Europe and Asia. And then we have our very own irises.
North American iris species
According to the United States Department of Agriculture, there are 28 North American irises: "Our native irises are found in every state in the lower 48 and Alaska. Most of our irises are inhabitants of Pacific coastal areas and the southeastern states." One of the most frequently encountered in the wild is Iris missouriensis, commonly called:
- wild blue iris
- blue flag iris
- Rocky Mountain iris
- Iris montana (synonymous but rarely-used botanical name)
Iris missouriensis is native to western North America, reaching as far north as Alaska. It was first cataloged by European Americans in 1806 when explorers Lewis and Clark came upon it alongside the Missouri River. As the Missouri Botanical Garden notes, I. missouriensis is named for the river, not the state; it isn't native to Missouri.
Natural resource agencies warn that with diminishing habitat—primarily saturated meadows, bogs, and wetlands—native iris species are at risk. Digging up iris plants on government-managed property is prohibited, and even seed collection requires a permit. Fortunately, we carry Iris missouriensis seeds here at Seed Needs, so you don't have to worry about breaking the law. Or, for that matter, getting your Spandex dirty.
Lore, Legends, and Symbolism
According to mythology, Iris is named for the Greek goddess of rainbows. She's considered Hermes' female counterpart: an intermediary between gods and mortals, and even between Hades and the living. She was associated with water, as is the plant borrowing her name, and like her, iris flowers can be any color of the spectrum.
Have you ever heard of the "Rainbow Bridge?" Some lore says the goddess used her shimmering, multi-colored cloak to create a bridge from Earth to Mount Olympus; others have interpreted this connection between the living and the celestial as the means by which we cross into the afterlife. Bifröst is the legendary Norse crossing between the realm of the gods and that of mortals; this, too, was a rainbow-hued bridge.
Want to be transported by a rainbow? I don't think you need a mythological feat of engineering to get you there. Put this song on your playlist while you're setting up your iris garden this spring. For good measure, sing while you're at it. Really loud.
The famous royal French emblem (fleur-de-lys) was derived from I. florentina and introduced by Louis VII in about 1150 for the second Crusade. In his standard and that of the following French kings, the three golden stylized iris (not lily) flowers on a blue background represented faith, wisdom, and heroism.
— Oxford Journal of Experimental Botany
Ancient Egyptian pharaohs adorned their scepters with carvings of irises to represent dominion, wisdom, power, and victory. In Japan, a blue iris symbolizes bravery, though the same represented death and adorned burials throughout the Mediterranean, including Turkey as late as the early 20th century. In Medieval European art, the iris represented protection against the devil's influence, and "St. Brigitta of Sweden (1307–1373) mentioned the sharp edges and tips of the leaves as symbolizing the pain of the Virgin Mary", according to the Oxford Journal of Experimental Botany, from which we pilfered all the information in this paragraph.
Here in the United States, the iris is the official state flower of Tennessee. It's the birth flower for February and the celebratory flower for 25th wedding anniversaries. Hopefully, the latter is in relation to bravery, not to dominion.
Iris' Medicinal and Practical Uses
We're hesitant to discuss the edible and medicinal properties of any plant family as diverse as Iris. Many species have traditional therapeutic uses, and some are used to create dyes and perfumes. Iris juice was believed to "cure" freckles, and ancient herbalists most frequently used the plant to cure edema. But most iris species are toxic when eaten (especially the roots).
Speaking of toxicity, the rhizomes of many irises contain high concentrations of pentacyclic terpenoids (zeorin, missourin, and missouriensin); the ASPCA notes that symptoms of poisoning in pets (and likely, in people too) are:
Iris in the Garden
Given the enormous number of iris species and the various climates to which they've adapted, we're going to focus on Iris missouriensis. This wild blue iris species is fairly typical of most grown in North American gardens, and given that it's threatened in its home environment, growing it from seed allows us to contribute to its preservation. But mostly, we're fans of I. missouriensis for purely selfish reasons: They rock. Almost as much as Iris donnieus sp. Pennsylvanius.
Each plant typically bears 1-4 variegated, violet-blue iris flowers (each 2-3" long) per stem. Each flower has 6 perianth segments: (a) three elongated spreading to reflexed falls have a central dark yellow-orange stripe and diverging blue lines on a white background and (b) three erect standards are narrower and lilac-purple to dark blue. Flowers bloom at the top of stout leafless stalks that rise up among dense, flexible, tough, sword-shaped leaves. Leaves typically rise above the flower stems.
We brought in the pros to identify the specific features of the wild blue iris flower since we didn't want to mess it up. What we can tell you, straight from the horse's mouth, is that most moisture-loving irises are easy to grow in the home garden if you provide them with the right environment and care.
Sunlight and moisture requirements
Irises prefer full sun, but in the hottest, driest regions, they do very well in partial shade. They prefer medium to wet (but not soggy) soil. Iris can tolerate end-of-summer drought, but they won't flower under dry conditions. We recommend keeping Iris missouriensis plants moist at least six weeks post-bloom to protect the plant's health and to allow the leaves to continue storing nutrients in the rhizomes.
Mulching around the plants—being careful not to cover any rhizomes above the surface—will help maintain soil moisture, and prevent severe temperature fluctuation.
Here are some quick facts to help you choose the right spot for your iris beds:
- USDA Hardiness Zones: Herbaceous perennial in zones 3 through 8
- Soil Preferences: I. missouriensis tolerates a very wide range of soils, as long as it's well-draining. Its ideal pH is between 6.0 and 8.0.
- Plant Height: 1' to 2' tall
- Plant Width: 3/4' to 1' spread
- Growth Habit: Upright, with spreading rhizomes
- Bloom Period: Roughly May through June
- Harvesting: Cut entire iris stems and immediately place them in water. Iris flowers make phenomenal floral displays!
Maintaining your iris plants
Keep your iris beds weeded, and when the flowers are spent, remove their entire stalks. Divide them every 2 to 3 years to prevent crowding. Let the leaves die back on their own at the end of summer, only removing them when they've turned brown; they're needed to feed the starchy rhizomes for the next season's production.
Iris pests and diseases
The biggest contributors to iris failure are overcrowding, poorly-drained soil, and inadequate sunlight. Iris plants are susceptible to a wide spectrum of fungal and bacterial "rots" if we ignore their basic needs.
- Bacterial leaf spot
- Bacterial soft rot
- Fungal crown rot
- Fungal leaf spot
- Iris mosaic disease
- Iris Borer
- Pill bugs (woodlice)
- Verbena bud moth
You can learn more about these critters and cooties, and methods of combating them, from the American Iris Society or South Dakota State University's article on the topic, Iris 911. Be sure to remove any plants that appear to be diseased, and either throw them away or burn them; never add diseased plant matter to your compost system.
Growing Iris from Seed
Why grow them from seed if you can get rhizomes from the local home improvement center? Iris rhizomes can be expensive if you have large plantings in mind, or if you're planning to grow them for market—either as a cut flower or as nursery stock. Rhizomes may carry diseases from parent stock or the soil from which they're collected, so the "blank-slate" mentality appeals to a lot of gardeners wary of dealing with problems inherited from someone else's bad cultivation practices.
Hobbyists enjoy the challenge, but if they don't know the tricks to get them to germinate, they give up and perpetuate the myth that irises are impossible to grow from seed.
Iris seeds are slow to germinate (28 to 35 days) and are subject to decay before they can get going. This is why we recommend planting 3 to 5 seeds per location, and then thinning them as they get established.
- Seed Treatment: Cold stratify your iris seeds for 30 to 60 days to trigger germination. Some guides recommend dunking the seeds in boiling water for about a minute at the end of the stratification process.
- Planting Depth: 1/16” to 1/8"; iris seeds require sunlight to germinate.
- Starting Indoors: Prepare biodegradable pots with a sterile seedling mix, and plant 3 to 5 treated seeds in each container. Place containers under artificial light in a 65°F to 70°F room, cold frame, or greenhouse.
- When to Plant Outdoors: Direct sow your iris seeds as soon as all danger of frost has passed.
- Seed Spacing: 18" in any direction. Map out a "zigzag" pattern to create staggered rows for the best effect.
- Days to Germination: 28 to 35 days
- Transplanting Tips: Plant the seedlings, biodegradable pots and all, being careful not to disturb the growing rhizomes. Give the pots a good soaking before you do, and consider gently scoring the sides to help the root system "break out."
Seed Needs: Your Responsible Source for Healthy Iris Seeds
Selecting healthy rhizomes can be tricky, but so can finding seeds from disease-resistant parent stock. We have you covered here at Seed Needs, where we work with sustainable producers of non-GMO seeds. Of course, genetic modification isn't an issue with native iris species such as Iris missouriensis, but quality sure is. And to provide you with the highest-quality viable seeds, we keep our stock in climate-controlled storage and only keep in our inventory what we can expect to sell in a single season.Are you planning on growing iris from seed this spring? Whether you're growing for your own garden, for market, or for gifts, contact us to find out how we can help you get started!