Water Irises | Irises | Collections | Průhonice Botanic Garden | Articles | iBotky.cz

Water Irises

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In 2013 we work on a new display bed dedicated to water irises.
Many thanks to a specialized American nursery Ensata Gardens for helping with preparations. They provided us a great discount on plant material.


Irises with elongated rhizome, the rhizomes keep residues of old leaves without significant strangulations. It is characteristic for foliage to have aerial tissue between fibers, which is visible as lighter color when looking against daylight.

Yellow Iris (Iris pseudacorus L.)

Yellow Iris is the most frequent iris species in wild nature of Czech Rep., it is also grown as water or marshy plant in gardens. It is native to whole Europe, Mediterranean and Central Asia, in China only in culture. It is a vigorous plant up to 1.5m tall with bifurcated rhizome. Foliage is sword like, having significant midrib, sometimes purple at base. Branching stem reaches 2/3 foliage length and it has 4 – 16 yellow flowers with brownish pattern. There are about 20 cultivars in culture looking very similar to the botanical species, ivory or white color are often (var. alba hort.). This characteristic is quite stabile and it appears when propagated by seeds.

            ´Berlin Tiger´(Tamberg, 1988) flowers has significant brown veining on the whole of petals

            ´Donau´ (Eckard Berlin) – vigorous tetraploid plant, yellow

            ´Flore Plena´ – double

            ´Foxcroft Full Moon´ (Katharine Steele, 1997) – creamy white ground, maroon eye zone

            ´Gubijin´ (Hiroshi Shimizu, 1999) – a special variety used for hybridizing with other iris species

             (I. ensata), botanicals hardly or ever cross with them

            ´King Clovis´ (Eric & Bob Tankesley - Clarke, 1994) – big flowers with broad outer petals

            ´Roy Davidson´ (Ben Hager, 1987) – yellow flowers with brown markings and veining

            ´Seakrill´ (Jill Copeland, 2004) – pale yellow, chestnut brown significant markings

            ´Variegatus´ – in spring leaves yellow variegated turning green later in the season

            ‘Leo Dudek’(Jiří Dudek, 2005) – creamy white Czech cultivar

Hybrids are known with species of I. ensata, I. fulva, I. laevigata, I. sibirica, I. spuria, I. versicolor a I. virginica, but they are very rare in the garden culture except Pseudatas = hzbrids with I. ensata. Yellow iris is carefree garden plant. It grows in water (submerged to 1/3), on marshy stands as well as in well watered garden beds. It makes seeds easily and it can run wild, which must be count on when planted in castle parks or natural landscapes with authentic local vegetation.


Rabbit-ear Iris (Iris laevigata Fisch.)

This iris grows in clumps up to 45cm tall. Stem has two reduces leaves at bottom part and mostly 3 branches, each with 2-3 glabrous flowers. It differs from I. ensata in foliage; leaves are wider (1,5 – 4 cm), more in a bow curve and they don’t have significant midrib. Flowers have narrower sepals. It blooms 2-4 weeks before I. ensata.

They can be experimentally hybridized with I. ensata, I. pseudacorus, I. versicolor, I. virginica, and also with Siberian Irises and Spurias (I. orientalis), but it is not common. Many cultivars are grown in Japan, sometimes called Kakitsubata Japanese Irises. They have different flowers in shape and color, can be double. They didn’t expand to Europe much, because their flowers weren’t as big and diverse as I. ensata. On the other hand they can be more frost and rot hardy. It can be grown as waterside plant or submerged in water to ¼.


Virginia Iris (Iris virginica L.)

This marsh iris has crawling rhizome and reaches up to 90cm, leaves are 1-4cm wide, stem has reduced bracts, it is branched but plants from the North doesn’t have to. Blue flowers have yellow spot with long significant whiskers on petals. Seeds are of oval or irregular (letter D) shape having corky dull skin. It grows on East of North America from Great Lakes to Florida.

Harlequin Blueflag (Iris versicolor L.)

Species similar to Virginia Iris, but it's slightly lower – 80cm and leaves are 1-2cm wide. Stem with reduced bracts branches in upper half out in 2-3 branches with leaves, each of them having 2-3 flowers. Flowers have whiskers on main veins. The main differential mark is seed surface, they are also D shaped but shiny with hard and thin skin. This iris can be found on the east of N. America around Great Lakes. 

Both of these irises have many forms which are different in color or spots on flower. They can be white, pink, violet or blue with significant veining, spots are mostly yellow at a base of a petal. They are a popular garden plant in N. America of many cultivars, less common in Europe, where Siberian irises are more often. They can be grown in well irrigated beds or on waterside, in full sun and in nutrient rich soil. Their features of broader leaves, flowers at foliage level and spreading growth give them less horticulture credit then to Siberian irises. Both species can hybridize in between as well as with Siberians or Louisiana irises.


Beachhead Iris or Arctic Blue Flag (Iris setosa Pall. ex Link)

It’s a clumpy plant, 60cm tall, crawling rhizome short and thick with old leaf remains, foliage 25cm wide, and stem with several branches. Sepals are reduced of a awl shape, upright and 1-2cm long. Seed pods have significant midrib; seeds are oval in diameter (not flat) and shiny. This iris comes from North Asia, Kamchatka, China, Japan and North America. In this great area, there are several varieties described. The species is very variable in flower color and it hybridizes with water irises and Siberians.


Japanese Iris (Iris ensata Thunb., syn.: I. kaempferii)

Japanese Iris grows in clumps around 1m tall. It has leaves 0,5-1,5cm wide with significant midrib, stem has 1-3 reduced leaves and poor branching. Flowers are quite big up to 15cm in diameter, purple to blue in wild. They grow naturally from Baikal, Sakhalin to North China and Japan.

Garden cultivars are marked as JI in American catalogues, sometimes called Hanashōbu group of Japanese irises. Introduction of this species was at first as a live calendar. Agriculture in Japan was ruled by natural phenomena: e.g. cherry blooming was the end of game season, irises in flower meant placing rice seedlings in fields. The oldest descriptttion of a wild iris was in Shugyobushu Collection of Poems written by Jien (1155 – 1225). First records of growing irises in culture were from a book Sujyaku Ourai by Kameyoshi Ichiso (1408-1481). He also mentioned natural color variations. In 1681 in Kadan-Komoku Book were a few cultivars described and later, in 1799, there were a few hundreds of them already. First introduction to USA was in 1869 by Thomas Hogg, followed by larger commercial import in 1877. Many bred varieties were brought to N. America and Europe and western breeders could follow up with it. They became very popular in the twenties of last century in USA, when lots of commercial growers held and hybridized them. Japanese Irises spread fast over the continent, so Cameron could mention in 1908 that “you can find them in almost every garden”. This interest in irises was interrupted by Great Depression and later by World War II and hatred of the Japanese. Its renaissance started in the eighties.

Tetraploid Japanese Irises didn’t come naturally from the wild; they were obtained in the sixties by using alkaloid colchicin. The first one ´Raspberry Rimmed´ was introduces by Currier McEwen in 1979 as a simple tetraploid of white color and raspberry red margins. He was followed by others like German Eckard Berlin and Japanese Mototeru Kamo, Hiroshi Shimizu, Teutonu Yabuya. These tetraploid irises have wider and darker leaves and more firm flowers. Czech breeders are Jiri Dudek (Caciga, 2000 and Promenada 2001) and Zdenek Seidl continues today with it (Fialovy Poprach, 1999 and Silesian Sky 2005).

Japanese Irises can give a gardener hard time. They can be more challenging than other groups of garden irises and even individual cultivars can have different requirements. That’s because breeding of these irises proceeded in different climatic areas of Japan. The biggest mistake is to grow them as water plants. The fact is that we know Japanese Irises from photographs as waterside plant in Japanese gardens, but these gardens are mostly from central and south of Japan, where milder winters are. In north Japan and Manchuria they prefer growing in damp meadows but not submerged in water. Growing conditions have to be same wise. They need rich soil, slightly acidic (pH 5 – 6,50) and lime free if possible. Abundance of lime causes leaf chlorosis and poor growth; even a level which could be normally harmless in garden soil. Sufficient nutrient supply is elementary for good growth and flowering. The best fertilizers are the same as for rhododendrons. Beware of salinization of soil. Transplanting should be done every 4 years into new bed. Best time for planting is spring, but if efficient care is provided, we can divide them anytime except for blooming season. Propagation at the end of fall and in winter isn’t suitable, because rhizomes can rot easily. To prevent it and to provide adequate water mode and frost protection, plant it this way. Rhizomes should be about 2cm below surface, covered with garden cloth and 10cm of bark mulch. Irrigation is needed in beginning of the season and when draught, try to keep them dry if possible in winter (in local conditions). Place them in sunny position with minimum of 6 hours of sun light a day.


Cultivars are divided according to flower shape:

1)      Single botanicals with back curled petals

2)      Single with flat flowers

3)      Double, flat, with sepals and petals of same size

4)      Full bloom with 9-12 petals in total


Translation: Marketa Machackova