Species Iris Group of North America

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Iris Of The Month!

Originally I thought this would be a fun thing to do & something that would be easy to keep up-to-date, but it turns out I was sadly mistaken. I was trying to alternate each month between bearded and non-bearded species. But as with all things real life gets in the way and I find 6 months has gone by since my last update. Yikes. I'm going to officially suspend updates for now and resume them in the future as time permits.


[October 2016 - Lapeirousia oreogena]

Just look at that color. WOW! It's not hard to understand why this little treasure is prized by those who grow it. This species is native to South Africa in the northwestern cape. It produces stunning purple flowers marked with symmetrical white and black patterns. The name oreogena means 'born of mountains' in reference to its native habitat.

This species is not terribly difficult to find in the trade. It is sometimes available in seed exchanges and it is sometimes carried by nurseries specializing in South African bulbs or fynbos plants. If you don't live in a suitable mild Mediterranean climate you'll have to grow this as a potted plant in a greenhouse. Fortunately it stays small so it is suited to that culture and a sandy soil is recommended.

If you're in a Mediterranean climate you should definitely try it!


[September 2016 - Iris foetidissima]

This unique plant is native to western Europe and coastal northwest Africa. It is most famous for it's colorful seeds which persist on the open pods throughout most of the winter. They range in color from pure white to deep red with most of them being somewhere in the yellow to orange range.

The flowers are often considered secondary by some gardeners but this is a shame. The flowers are quite beautiful and delicate in their own right, even if they aren't as colorful and big as other types of irises. Typical flower colors range in the yellow to lavender range, and where these colors overlap the result is a tan color.

This species needs filtered shade. Too much sun will scorch them. This species also needs protection from cold winters. Not all varieties are cold hardy to Zone 6, so plan to give them winter protection if you live in a place with bad winters.

There is a stunning form with variegated foliage on the market but it is reported to be a shy bloomer.


[August 2016 - Tigridia pavonia]

This lovely irid is native to Mexico. It is frequently sold in the United States under the common name Mexican Shellflower. They are not cold hardy but the bulbs can be lifted & stored cool and dry in winter.

Flower colors range from red to pink to yellow to orange to white. They are very eye-catching when in bloom. Bulbs are readily available via mail-order nurseries and local garden centers. The plants are easy to grow from seed as well and will typically bloom in the first season.

They do best with adequate watering throughout the summer especially if there is an unexpected drought. If you wish to get seeds be sure to hand pollinate your flowers as the native pollinators may not be adapted for the job.


[July 2016 - Iris hartwegii]

Iris hartwegii is a species endemic to California. It is found in the foothills of the western Sierra Nevada Mountains in central California and in the San Bernardino Mountains in southern California. This is a member of the Pacific Coast Irises often referred to as the Californicae group.

They have yellow or lavender flowers and generally bloom shorter than 12 inches. They grow well in full sun or partially shaded areas. In the wild they are often found in proximity to streams.

Unfortunately they are not adapted to grow in climates that differ from their native range. But if your climate is similar to central California then you should give them a try. They are occasionally available in seed exchanges such as NARGS or SIGNA, or from speciality nurseries.


[June 2016 - Sisyrinchium angustifolium]

Sisyrinchium angustifolium is native to eastern North America. It has the common name of blue-eyed grass. The flowers are rather dimunutive, however an established clump will produce dozens of them in succession. They are readily pollinated by native bees and can spread slowly by seed in the garden.

Sisyrinchium continue to gain popularity and are becoming increasingly available through mail-order nurseries and at garden centers. This particular species does well in regular garden conditions from full sun to nearly full shade. Old clumps can become quite large.

Because the plants are relatively small it can be difficult to distinguish the different species apart. Leaf size, flower size, flowers per umbel, habitat, and spathe configuration are typically used as key features.


[May 2016 - Iris cristata]

Iris cristata is a woodland species found in central and southern Appalachia westward across the Ohio and Mississippi River Valleys to the Ozarks of Arkansas, Missouri, and Oklahoma.

It grows in habitat very similar to Iris verna, and they even appear similar when in flower. However Iris cristata is easily distinguished by the fleshy crests (from which it gets its name) on the falls.

In the wild it can be found growing in the moist leaf-litter and shade of deciduous trees. It blooms in spring before those trees have leafed out. In cultivation it can be grown in other conditions, but it's best to provide similar leaf-litter and filtered shade.

Its closest relative is Iris lacustris. There are no known hybrids with other species.


[April 2016 - Ferraria crispa]

Ferraria crispa is native to South Africa. It produces tall leafy flower-spikes adorned with strange spidery-looking flowers on top. Flower colors are variable and range from creamy-brown to yellowish-brown to greenish-brown to marroonish-brown. Flowers are heavily frilled and strange in appearance, often called starfish-like. They bloom in late winter or early spring.

Some people claim the aromatic flowers are foul smelling, but many people claim the flowers smell good! The flower shown here was faintly scented and it was pleasant.

It will be a care-free perennial in any Mediterranean-like or mild climate. It will not survive cold winters and it also needs hot dry summers. They make excellent indoor conservatory plants and are common residents at botanical gardens.


[March 2016 - Iris verna]

Iris verna is a woodland iris found in the foothills and mountains of Appalachia from southern New York down to coastal Alabama. Disjunct populations also exist on the western side of the Mississippi River in western Arkansas and central Missouri.

Superficially it looks strikingly like Iris unguicularis when in flower, but genetically it is not closely related. In fact it genetically distinct and considered to be in a monotypic series of its own, with a closer relation to the bearded irises.

In the wild it is found along dry ridgetops and slopes under the shade of deciduous trees. It blooms in spring before those trees have leafed out. In cultivation it can be grown in other conditions, but it's best to provide it good drainage with filtered shade. If you can replicate the dry ridge top or ridge slope conditions you should have even better success.


[February 2016 - Gladiolus splendens]

Gladiolus splendens is native to South Africa. It produces tall spikes of bright red flowers on dark stems from late winter to early spring. Shown here is a close-up of two flowers in profile. This flower shape is unique in the genus and was cause for it originally to be assigned to another genus.

It will be a care-free perennial in any Mediterranean-like or mild climate. In harsher climates (Zone 8 and colder) the corms should be lifted and stored for the winter. In climates with excessively wet summers take measures to provide excellent drainage (for example, growing in pots).

In their native land they are pollinated by sunbirds. Throughout the Americas they should attract hummingbirds. Seeds of this species are available in this year's seed exchange. See item 15XX166.


[January 2016 - Iris glaucescens]

Iris glaucescens is a bearded iris species from central Asia. It is little known to the gardening world outside of its home range, but with the help of social media many of us are finally getting to know this beautiful iris.

In fact this photo comes from a Russian iris enthusiast named Andrey Dedov who posted dozens of photos to Facebook that he took in the Altai region of southern Russia in 2014. The variability of the flower is striking. It comes in a wide range of colors from white & yellow, to pale blue, to violet, and purple.

Hopefully seeds will become available soon for European & North American gardeners to try growing it. With its Central Asian origins it would require dry winters and hot summers to thrive. But who knows, maybe it will be more tolerant and adapatable than expected?


[December 2015 - Dietes grandiflora]

Dietes grandiflora is native to South Africa. Although the flower looks just like an iris, this species is actually an irid. All members of Dietes are from the Southern Hemisphere. All members of Iris are from the Northern Hemisphere. This particular Dietes should grow well for anyone living in a Mediterranean-like climate. In some regions of Australia it grows too well and has naturalized and become a pest.

It is fairly easy to find in commerce. If your local garden centers don't carry it, you can buy it via mail-order. Sometimes it's offered in the SIGNA seed exchange, too. There is a variegated leaf form that is quite appealing.

The multi-colored flowers (white, yellow, and violet) last for several days making it an excellent choice if you are new to growing Dietes. Reportedly it performs best if grown in dappled shade.


[November 2015 - Iris hexagona]

Weirdly, Iris hexagona is one of the hardest native American irises to find in commerce. It's a shame because it is a GREAT addition to any water garden. So you may have to hunt pretty hard to find a nursery with it in stock. It is even uncommon in the SIGNA seed exchange, whereas other Louisiana Iris species are offered routinely year after year.

It is native to the deep south of the USA from South Carolina to Florida to Texas. Despite this southern heritage it is perfectly adaptable to northern gardens. In fact predation by rodents under snow cover in winter is a bigger threat than cold temperatures. It comes in mostly shades of dark blue to pale blue and white, and it grows to average height for Louisiana Irises in general.

Historically speaking this was one of the first new Iris species from North America to be described scientifically. Consequently it has an entire section named after it, Section Hexagonae, the Louisiana irises.


[October 2015 - Alophia drummondii]

This stunningly beautiful irid is the northern-most representative of its genus. It occurs naturally in northeastern Mexico and the southern central part of USA, reaching as far north as Oklahoma and Arkansas. Unfortunately it is not hardy any farther north than that, but ought to be able to grow in most any other Zone 8 climate. It's feasible, but difficult, to store it potted in a basement over winter in colder climates.

The SIGNA seed exchange sometimes has it for sale, but otherwise only specialty nurseries carry it. They are perennials and form bulbs which are dormant over winter, but usually in commerce you will only find it for sale as seeds. With some skill and patience it can be grown as an annual in the north if you are diligent about collecting the seeds.

The huge two-inch flowers are fleeting, lasting only a day, but they are so enjoyable to behold. In this photo the flower is backlit which shows off the amazing colors and patterns.


[September 2015 - Iris x norrisii]

This beardless iris is a hybrid between Iris domestica and Iris dichotoma. And like its parents this iris blooms in the summer months long after traditional irises are finished blooming.

It is perfectly hardy and well suited to gardens in colder climates. Grow it just like regular bearded iris cultivars.

Flowers color range has expanded quite a lot since this hybrid was first created. Most are orange and yellow, but new ones are coming out in pink, purple, brown, white, and light blue.

They are becoming quite popular at garden centers and mail order nurseries. It's not hard to find seeds or plants for sale. New cultivars often command a high price especially if they are new color breakthroughs. They're fertile so you can grow and develop your own new color combinations from seed. Try it! And get rich quick. ;-)


[August 2015 - Trimezia martinicensis]

At first glance Trimezia martinicensis looks like a yellow-flowered member of the more common genus Neomarica. However Trimezia are distinctly yet subtly different from Neomarica in having cylindrical flowering scapes rather than flat.

Confusion also exists between Trimezia martinicensis and the closely related Trimezia steyermarkii. Leaf width is a good indicator with T. martinicensis at a narrow 1.3cm and T. steyermarkii at 2.5-3.4cm. Subtle differences also exist in the colors and shape of the flower tepals, with T. martinicensis being folded inwards and having brown marks and T. steyermarkii are bent outwards and have purplish-brown marks.

Coming from the tropics Trimezia are best suited as indoor houseplants if you live in a temperate climate. If you find one in your local garden center you should try it out.


[July 2015 - Iris tridentata]

This beardless iris species comes from the coastal parts of the southeastern United States ranging from North Carolina to the Florida panhandle. USDA Plants Database also reports it from Tennessee which is far inland, but doesn't specify the county distribution. It is frequently found in association with Sarracenia pitcher plants. The two make excellent companions in the garden!

It is by far the latest blooming of all the eastern American species. In Ohio, Zone 6, it starts blooming in mid-to-late June and stops in early July.

Flowers are typically purplish-blue with white and yellow signals. The falls are typically wide and showy. The style arms are highly recurved and decorative. The standards are whisker-like threads or teeth, and the reason the species is named tridentata.

It has recently been successfully crossed with Siberians to produce a whole new class of Spec-X called 'Sibtatas'. They have not been known to cross with any other species, although this potential has yet to be fully explored.


[June 2015 - Ennealophus euryandrus]

This delightful irid is endemic to Argentina in South America. It seems to be recently new to cultivation at least in North America. A few specialty nurseries and seed exchanges occasionally have it on offer.

As such there are not a lot of people growing it, and not a lot of information on its preferred growing conditions. It is not winter hardy in cold climates, but it can be grown from seed. Try to provide your plants with partial-to-full sun & frequent watering in well-drained conditions.

Well grown plants will reach about 1.5 feet tall and bloom for several months from spring to summer. Hand pollinate your flowers to ensure seed production as your locally native insect pollinators may not be successful with these strange flowers. If you are successful growing and propagating this species, please share!


[May 2015 - Iris attica]

This bearded iris is a miniature dwarf species native to southeastern Europe from Greece to Croatia to Turkey. It is closely related to Iris pumila (occasionally listed as Iris pumila subsp. attica) but the chromosome counts between the two species are significantly different.

In Greece the species is completely summer dormant as it typically grows on rocky hillsides which do not receive rainfall in the summer months. It is also not hardy enough to withstand cold winters so it is best grown in places with suitable Mediterranean-like climates.

Flower colors and patterns vary greatly and are typically yellow or purple or a blend of the two. White colored beards seem to be prevalent, but sometimes they're yellow or purple. The foliage is noticeably sickle-shaped.


[April 2015 - Sparaxis elegans]

This stunningly colorful irid is endemic to South Africa where it is classified as 'Vulnerable' on the South African Red List. Its primary threats are overgrazing by livestock and habitat loss due to agriculture.

Fortunately these are easy to grow in cultivation, and have been in cultivation since the 19th century. They can be grown outdoors in USDA Zones 9-11. The most important thing to remember is to withhold all water in the summer, which is the plant's natural dormancy period, otherwise the corms will rot. This is a very common cause of losing plants in cultivation.

In the wild the flower colors range from pure white to bright orange to pink. All of these variants have violet colored centers outlined in black, sometimes black & yellow.


[March 2015 - Iris versicolor]

This beardless iris is native to eastern North America. It comes in a range of colors mainly in blends of white, blue, violet, and purple and always with a small yellow signal. It's closest relatives are Iris virginica & I. setosa which also inhabit eastern North America. It's also closely related to I. laevigata, I. ensata, and I. psuedacorus, which come from Asia & Europe.

In the wild it grows in wetlands. In the garden it's tolerant of drier conditions, but for best vigor and bloom it must be grown in full sun & wet conditions (ideally on the edge of a pond). It grows well from USDA Zones 3-9, and possibly even Zones 2-10.

In 2004 the cultivar 'China West Lake' won the prestigious Founders of SIGNA Medal. Then again in 2006 that medal was awarded to the cultivar 'John Wood'. And again in 2010 it was awarded to a cultivar named 'Raspberry Slurp'.

Trimezia martinicensis photo by Rodney Barton. Iris tridentata photo by Ken Walker. Ennealophus euryandrus photo by Rodney Barton. Iris attica photo by Yannis Bourodimos. Sparaxis elegans photo by Elias Chasiotis. Iris versicolor photo by Dennis Kramb.

© 2016, SIGNA. For general inquiries about SIGNA please contact krw25@cornell.edu. Please report technical problems to dkramb@badbear.com.