Monday, November 16, 2009

The Rainbow Of Irises

Irises are truly aristocrats in the garden.  The ornate flowers in luscious shades inspired monarchs to include them in their flags and coats-of-arms.

The genus, Iris (pronounced EYE-riss), includes at least 200 species native to just about everywhere within temperate zones in the northern hemisphere.  The name comes from a Greek mythological goddess who personified the rainbow, communicated between divinity and humanity, and raced along just out of reach.

Irises can be found growing in habitats as diverse as cool, mountainous regions and warm, subtropical swamps.  Some are drought-tolerant while others grow in water up to 10" deep.  Most irises prefer a site with full sun and well-drained, moderately fertile soil.  Many are cold hardy down to -15F.  Therefore, you should be able to find a type that will perform well for you.

As the name suggests, "iris" is synonymous with color, and they are myriad. Shades range from white to pink, blue, lilac and purple.  Some are yellow, scarlet, orange or nearly black.  Others display bold combinations of colors.  Most flower for about a month in late spring and early summer.  But, with careful selection, you can have iris blooms from very early spring to mid-fall.

They are absolutely lovely in the garden, regal in appearance.  In my opinion, irises are best displayed when planted in groups of a single color.  Different groups may be of various colors.  The resulting masses of bloom will captivate even the casual passerby.

The blooms certainly command attention, but foliage is as useful as the flowers.  The long, sword-like leaves provide a strikingly simple contrast to many of the shapes and textures found there.  The same features also make them very popular in cut flower arrangements.

The majority of irises are rhizomous plants.  Rhizomes are thick, fleshy stems that grow horizontally just below the soil surface giving rise to leaves, flowers and roots.  Other irises grow from bulbs.  Dutch irises are bulbous.

It's beyond the scope of this article to delve into all the species and hybrids.  I'll stick to some species most popular and readily available.

German irises (I. germanica), especially the hybrids, are widely grown.  Germanica (pronounced jer-MAN-ih-kuh) means "of Germany."  They produce multiple, huge flowers on forked stems held above the silver-grey foliage.  German irises are included in a group called "bearded" irises.  The "beards" are the hairs on the the "falls".  "Falls" are the three drooping sepals located under the upright petals.

Dwarf bearded irises may be as short as 6".  The taller varieties range from 36" to 48".  They prefer pH ranging from 6.1 to 7.8, and require only mildly fertile soil.  Planting depth is very important:  the top portion should be right at soil level.  Space them 12" to 24" apart.  Bearded irises require full sun, and prefer dry conditions during the summer after flowering is completed.  Because they are drought tolerant, they are ideal for xeriscaping.  (Xeriscaping is the garden practice that seeks to reduce the need for irrigation.) German irises generally do well in climate zones 3-9.

Iris pallida (pronounced PAL-lid-uh, meaning "pale") is another bearded iris.  Common names include Dalmatian Iris and Sweet Iris.  It's native to the rocky coast of what was once Yugoslavia.  Flower color is pale blue.  A variety with lovely variegated foliage is quite beautiful.  Height ranges from 18" to 36".  It thrives in USDA climate zones 3-8.  Plant 12" to 24" apart in full sun and well-drained soil with pH ranging from 6.1 to 7.8.  In addition to its ornamental interest, I. pallida is also cultivated for the essential oil in the rhizomes which are processed and sold as "orris root."

Beardless irises are found in many other species.

Siberian irises, Iris sibirica (pronounced sy-BEER-ih-kuh) are native to eastern Europe and northern Asia, as the name suggests.  They grow 24" to 36" tall.  The foliage is slender and grasslike.  Flower colors are purple, lavender, burgundy, yellow or white.  They prefer rich, well-drained soil in full sun, but they will tolerate more moisture than German irises.  Space them 18" to 24" apart.  They tend to grow in clumps.  Preferred pH ranges from 6.1 to 7.8.  They do well in climate zones 3-9.  Masses of single colors planted near a watercourse are dazzling sights.

Japanese irises, of the species I. ensata (pronounced en-SAH-tuh or en-SAY-tuh, meaning "sword-shaped"), are absolutely stunning.  Native not only to Japan, they are common in parts of China, Korea, India and eastern Russia.  Their large, horizontal blooms may be up to 8" across and resemble enormous butterflies.  Colors may be solid, mottled or marbled in rare combinations of exotic shades of blue, white, pink, yellow, and reddish-purple.  Height is 24" to 36".  They require evenly moist soil with pH ranging from 6.1 to 7.8.  They're great for wet places like bog and water gardens, and will grow in water to 4" deep.  Japanese irises will tolerate full sun or partial shade.  They do well in climate zones 5-9.  Space them 18" to 24" apart.

Iris pseudacorus (pronounced soo-DA-ko-rus, meaning "false sweet flag") is commonly called Yellow Flag.  The species is native to Europe, western Asia and northwest Africa, but are naturalized in parts of North America.  Yes, they are of one color:  yellow.  But they'll knock your socks off in spring and early summer.  They require full sun and wet places, growing in water up to 10" deep.  These are also excellent for bog and water gardens.  Best pH ranges from 6.1 to 7.8.  If simply planted in consistently moist garden soil, they will perform, but the flowers will be smaller.  Height ranges from 18" to 36".  Yellow Flag irises are easy to grow in climate zones 5-9.  Plant in full sun to partial shade.  Space them 18" to 24" apart.

Iris versicolor (pronounced VER-suh-color, meaning "variously colored"), sometimes known as Blue Flag, Water Iris or Harlequin Iris, is another that has very high moisture requirements.  It is native to North America, thriving in USDA climate zones 5-8.  Cultural requirements are the same as for I. pseudacorus.  For those who wish to grow native species, this one is ideal.

Iris cristata (pronounced kris-TAY-tuh), also known as Crested Iris or Blue Flag, is native to the Eastern United States.  Flowers are lavender-blue with white or yellow crests.  Blooms appear in spring.  Blue Flag grows to only 4" high and spreads vigorously in all directions, so it makes a fine ground cover in a natural setting.  Plant 3" to 6" apart in partial shade in USDA climate zones 3-8.  Soil must be consistently moist soil (not soggy) with pH ranging from 6.1 to 7.5.

Roof irises are relatively little-known plants that get their name from an unusual habitat:  the thatched roofs of simple Japanese country houses.  They are of the species, Iris tectorum (pronounced tek-TOR-um), which means "on roof".  Actually, they are native to China, but usually associated with Japan.  It is said that Japanese women used the ground powder of the rhizomes for cosmetics.  Perhaps limited growing space forced them to grow their face powder on their roofs.  The plants grow to 12" tall and display lavender-blue or white flowers in late spring and early summer.  Flowers are about 3" across.  Roof irises grow in USDA climate zones 5-9.  You don't have to have a thatched roof to grow them.  Plant in full sun to partial shade, spacing 8" to 12" apart.  Preferred soil pH ranges from 6.1 to 7.8.  Garden soil high in organic matter and slightly moist is fine.  Take care not to over-water.

Dutch irises are elegant plants producing large, graceful blooms.  Their botanical name is Iris x hollandica (pronounced haw-LAN-dik-uh), named for the country where they were hybridized.  They are beardless.  No cutting garden should be without them as they are superb in flower arrangements.  Colors are white, blue, purple and yellow, often in combination.  Mass beds of dutch irises are gorgeous, but they also make great companions to other bulbs and perennials in borders.  Soil should be well-drained and in a sunny location.  They are perennial in USDA climate zones 5-9.  Moist, well-drained soil with pH ranging from 6.1 to 7.8 is best.  Plant the bulbs in fall, 4" deep and 3" to 6" apart.  Take care not to over-water.

Reticulated irises are of the species Iris reticulata (pronounced ree-tick-you-LAY-tuh), which means "netted", referring to a pattern on the bulbs.  They are native to Iran, Iraq, Turkey and environs.  These are among the earliest blooming irises, making them especially welcome when you've had enough of winter.  Plant height is about 6".  Colors are blue or purple.  They thrive in USDA climate zones 3-9.  Plant them in full sun to partial shade, spacing 3" to 6" apart.  Slightly moist soil with pH ranging from 6.1 to 7.8 is fine, but avoid soggy soil.  A dry period is required after bloom time.  Growing them in raised beds is recommended.  Because they are compact in size, reticulated irises are perfect for container gardens.

Iris histrioides (pronounced hiss-tree-OY-dayz, meaning "like an actor") is similar in many respects to Iris reticulata.  The bulbs are also netted, they bloom very early and are native to the Caucasus region.  Colors are shades of blue.  Cultural requirements are nearly the same as for I. reticulata.  They thrive in USDA climate zones 3-8.

Iris danfordiae (pronounced dan-FORD-ee-ay) is yet another species similar to I. reticulata.  It is named in honor of Mrs. Charles Danford, 19th century plant explorer and wife of the noted artist and ornithologist.  Also known as Buttercup Iris, the color is yellow.  Cultural requirements are practically the same as for the other "netted" irises, but it is not as cold-hardy, thriving in USDA climate zones 5-9.

With so many species, hybrids and cultivars to choose from, you are bound to have a place to grow irises.

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