Saturday, August 21, 2010

Not Your Average Bearded Lady

Bearded irises are sorted by size into several categories. Miniature dwarf reach a height of 8” or less and their blooms are around 1-2” in diameter. Standard dwarf get 8-15”, intermediate reach 16-27”; miniature tall (excuse me?) grow to 16-25” and produce small flowers; border iris are 16-27”. The grandes dames are tall iris (is that tall? Or tall tall? Big tall?) that can reach 38”. Bearded iris tends to bloom by size in order from smallest to largest.

So, as a miniature dwarf, Iris pumila is one of the earliest blooming of the rhizomatous irises. Though not nearly so early as the tiny reticulated irises, I. pumila shows promising buds before the end of March and can be in full flower in April.

Iris pumila is a natural hybrid between Iris pseudopumila and Iris attica that is native to central Europe. Its native habitat is dry grassy lands; like other bearded iris it loves to bake in the sun and hates wet feet.  A raised bed or rock garden will insure perfect drainage. Place this tiny titan at the front and give it room. Division is usually required in the third or fourth year; you will want to do it as soon as the blooms have faded. If you must fertilize be sure to use low nitrogen and be stingy.

Iris pallida, sometimes called sweet iris, orris or Dalmatian iris, is native to the Dalmatian coast of Croatia.  This rhizomatous bearded iris produces fragrant, pale lavender-blue flowers with yellow beards. In late spring to early summer, blooms appear atop stems which may get to 40” tall. I always thought that ‘Variegata’ had cream and green variegation and ‘Aureovariegata’ was green with yellow stripes. According to the Missouri Botanical Garden, these two varieties are synonymous and feature gray-green leaves variegated with stripes of creamy yellow. Despite its association with the tricky bearded iris clan, it has been selected as a GPP for the Pacific NW.

To make things more confusing, Iris pallida ‘Argentea Variegata’ (aka ‘Albo viris pallidaariegata’) does have pure white variegation attributed to its leaves. However, the GPP organization characterizes this variety as less vigorous than ‘Variegata’. Whatever variety you choose, this is one iris whose foliage is more beautiful than its bloom-and since the bloom is both pretty and fragrant, it is a no-lose proposition.

Iris unguicularis (née Iris stylosa) is the winter blooming Algerian iris. It often starts in October and produces blooms through March or even April and is considered hardy in zones 7 to 9. When the temperature dips below about 10 degrees, however, any flowers and buds will freeze and be lost. Happily, if the weather warms up, the plant will re-bud and be in full bloom again within a week.

Iris unguicularis has tough, sometimes ribbed, leaves ½” or less in width and anywhere from 1-2 feet long.  The plant can be unprepossessing, but the flowers are dramatic-especially in the dead of winter. Blooms tend toward shades of lavender but can be pure white to deep purple to slightly reddish. The flowers are sweetly scented and can be cut and brought inside.

This iris is native to the dry Mediterranean climate. It is a bit tender and if the temperature drops to 0° F. the foliage will die to the ground. Usually it will recover and in the spring grow new foliage. I. unguicularis can survive the winter cold and even the steady rain of the PNW, but it requires excellent drainage and a good baking in the hot summer sun. If you plant it against your foundation on the south side it will enjoy the heat, stay dry in the summer and the lime leaching from the concrete will contribute to the neutral to slightly alkaline soil it prefers. At the least try to find a south facing section of your garden in the full sun.

It resents drying out completely; you may need to water once or twice during the summer if there is no rain. The flowers are held low in the evergreen foliage and you might want to cut it back to about 10” in late August so that you can enjoy the flowers. Like most irises, a low nitrogen fertilizer can be applied before and then after flowering. The biggest problem you face with this unique iris is slugs. Imagine their delight upon finding this treat in midwinter. You must be diligent about baiting for slugs or you may never see any flowers.

Iris unguicularis may be propagated by dividing the rhizomes, but I have found in my garden this plant is slow to colonize. You can also allow the seed pods to dry on the plant and collect the seeds or allow the plant to self-seed and then move the seedlings. It may take two or three years for the plant to produce flowers.

What an amazing genus. You can have some kind of iris blooming almost any month of the year if you are willing to hunt for them!

Tuesday, August 17, 2010

Recalcitrant Rhizomes

The time has come to face the music and talk about the difficult but delectable rhizomatous irises. Iris germanica is the most familiar and probably what you remember seeing growing with wild abandon in hot sunny climates. Almost all bearded iris hybrids descend from wild forms of Iris pallida (Sweet Iris) and I. variegata (Hungarian Iris).

The model for the fleur de lis, blossoms of this stately beauty are instantly recognized. Three upright petals are called “standards”, and three pendulous petals are called “falls”. The falls are adorned June 005with bristly hairs that earn this lovely lady the moniker “bearded.”  Bloom stems carry multiple buds that flower in succession and make them desirable for the vase. Many of them are wonderfully fragrant. "Remontant" Iris, or "Reblooming" Iris  have a genetic tendency to bloom a second time in late summer or fall.

Bearded Iris have a reputation for being sturdy, long lived and low maintenance. Why do they turn into such prima donnas in the PNW? They don’t like clouds and they don’t like wet feet. Bearded iris will endure droughts with finesse, but they cannot tolerate soggy soil. They require baking in the hot, full sun with their rhizomes exposed like sunbathers on the beach at Nice. (Some people should not go topless. I’m just sayin.)

Still, they can be grown successfully here. Make sure the spot you choose has full sun and good drainage. As much as 50% of the rhizome should be above ground; planted too deeply they produce leaves but no blooms and are more susceptible pink iris to soft rot and iris borer. Do not mulch them or they will sulk. Planting on a slope or in raised beds improves drainage. It may help to dig your hole, form a mound at the bottom, and lay the rhizome with the roots splayed down the sides. Firm the soil around the rhizome and then water to help settle the soil. Once established, Iris don't require watering. Overwatering is strictly verboten.

Irises thrive in almost any type of soil provided it is well-drained. You may fertilize in the early spring, if you like. Iris enjoy bone meal, superphosphate or any good 6-10-10 fertilizer. Be sure to avoid using anything high in nitrogen, as nitrogen encourages rot problems.

If, despite your best efforts, your iris leaves look tatty after bloom, remove them immediately. In the late fall or early winter, cut healthy leaves back to about six inches. Avoid using mulches, ground covers, or anything that covers your rhizomes or they will rot. Excessive moisture and rainy or humid weather can lead to yellow and brown leaf spots. Always remove old dead leaves, and cut off and destroy any leaf or part of a leaf that is affected.

When your iris clumps become crowded, the bloom will taper off and they must be divided. Dividing every 3-4 years should prevent a season without bloom. The best time to divide your013 iris is August. Save divisions from the perimeter of the clump and cut the leaves back to one third when replanting. You can dig the clump or, if you are confident in your excision skills, you may remove the centers of the clumps with your spade and leave the newer growth undisturbed. Remember that about 25% of Iris won’t bloom the  first year after planting. Sometimes they need an extra year to become established.

Give your German Iris plenty of sun, great drainage and room to bloom and they will make you proud. A little Wagner played full blast in early summer with the windows open won’t hurt.

Monday, August 9, 2010

An Iris by any other name is still an Iris

I’d like to introduce you to some of the more eccentric members of the iris clan. These iris are all well suited to our misty, moisty PNW; several are even considered pond or bog plants. With a little fortitude, you should be able to hunt them down. Don’t forget plant sales, they are an excellent source of the more unusual flora. The Snohomish County Master Gardener Plant sale is usually the Saturday the weekend before Mother’s Day in May.

Iris setosa var. arctica is one of my favorites. This tiny but lovely iris has grassy leaves and lavender to purple blooms with arresting silver veining. It’s ideal home is a situation where it won’t be crowded by larger plants, in full sun with moist soil. However, it is easy going and sturdy and will tolerate almost any soil, part shade and average moisture. This plant is native to Alaska, British Columbia and Siberia.

Iris ensata (Japanese Iris) can  live in partial shade but prefers bright, sunny locations. Ideally, they thrive in moisture-retentive, acidic soils with plenty of humus but they will grow well in any decent soil if they receive enough water. They require high soil moisture and can even be grown in  containers in pond ledges. They are grown this way to great Iris ensata at Oregon Gardeneffect at the Oregon Garden. Apparently, in winter they are narrow-minded about standing water or even boggy soils where rhizomes may rot. Plants may be grown in pots sunk half way in water during the growing season and then removed for fall and winter.

Iris foetidissima (Gladwyn iris) is well suited to the PNW. It is usually grown for its striking orange fleshy seeds in late autumn and early winter and not for its relatively insipid blue flowers. There is a variegated variety listed as a Great Plant Pick that is grown for its lovely evergreen white striped foliage because it rarely flowers and therefore, rarely sets seed.

Iris chrysographes is the bewitching black iris. Some call it a Siberian iris but, although it is similar in appearance, it hails from China, not Siberia. It grows in full sun to part shade and, like the Japanese iris, enjoys moisture and can even be grown pond-side.

Iris cristata (dwarf crested iris) is native to the United States typically appearing on rocky, wooded slopes and along streams. It prefers organically rich, moist but well-drained soils in full sun to part shade. It will tolerate almost full shade but if grown in full sun, the soil must be kept consistently moist. This is a vigorous spreader that grows 3-6” tall with nearly stemless flowers. If well pleased, it forms dense colonies that produce a spectacular drift of blue in the spring.

The Louisiana iris originates, as you might expect, from the gulf states of the US bLA Iris From SLI websiteut they are hardy to USDA zone 5. Natural hybridization occurred within five wild species originally found in the bayous of the Louisiana basin resulting in an astounding variety of colors and shapes. Not only hues of purple, blue, yellow and white are represented but also copper, peach, pink and almost red. Some have thin petals, some have upright standards, others are extremely wide and flat. I am on full hunt for this beautiful creature! Learn more about the history and origin of this fascinating plant at the Society for Louisiana Irises.

They will grow in full to part sun and the wetter the soil, the more vigorous the growth. They may be grown in average garden soils but prefer moist soils or submerged in a pond. They are relatively heavy feeders and will enjoy a balanced fertilizer in fall and again in late winter. After blooming in spring, the plant will go dormant and you may trim the foliage back to 2-3” above the ground.

Iris tectorum (Japanese roof iris) comes in shades of lavender and there is also a white form. It has fans of wide, ribbed leaves with a thin texture. It grows in full to part sun, but prefers woodland conditions with humusy soil and moisture. It appreciates compost in the fall and a light, balanced fertilizer in the spring, but is a sturdy and adaptable plant.

Truly, these intriguing plants are worth searching for!

Saturday, August 7, 2010

Luck of the Iris

Never one to seek controversy, I nevertheless must admit that I admire the genus Iris. Among the 250-300 species, there are a wide variety of types to choose from and all, in my opinion, are beautiful. Most are fragrant and many are long lived. They divide easily and come in an astonishing array of colors and seasons of bloom. The name Iris first belonged to the Greek goddess who was the personification of the rainbow and was bestowed on the genus as a reference, no doubt, to the wide variety of hues to be found there.

Certainly, many irises are a challenge to grow in the cool and cloudy Pacific NW. Some gardeners eschew these lovelies because they require heat, drainage and sun and their foliage has a tendency to become tatty and unkempt. So, I will start with the easy going, mostly non-rhizomatous types that are less intransigent.

Iris r. 'Harmony'Dwarf Irises include winter blooming Iris reticulata, I. danfordiae and  hybrids which I covered in a previous post. These bulbous iris are only 4-6” tall, so you must plant them where they may easily seen in the winter and very early spring. Happily, most of the perennials have yet to emerge when these iris bloom in January and February, so although they are small, their bright colors may be seen at a distance. The grassy leaves may continue to grow to 18” after blooming, so site them where you can hide their ripening foliage.

Dutch Irises grow from bulbs and bloom in mid spring. Both Iris xiphium and Iris x hollandica are commonly called Dutch Iris. (Iris xiphium is also called Spanish Iris; this is why I prefer botanical names!) They have long straight stems and lovely blooms so they are frequently used in floral arrangements. Like most iris, they require excellent drainage and prefer full sun but can be grown in part shade. Like most bulbs, the foliage must be left to ripen on the plant and store food in the bulb for next year’s bloom. Don’t remove the foliage until the leaves are yellow. You may lift the clump at that time and separate the bulbs to propagate.

Siberian Iris tolerates a wide range of conditions, thriving in damp and even wet areas. They are most floriferous in full sun, but also bloom in partial shade. They’re not bothered much by iris borer, bacterial soft rot or other iris problems. Their roots are more fibrous than the fleshy rhizomes of bearded iris.

Iris s. 'Butter and Sugar'Known for their graceful appearance, Siberian irises produce arching  grass-like leaves that stay green all summer. In late spring they produce delicate beardless blooms in shades of maroon, white, pink, blue, purple, and yellow. Siberian iris may need to be divided every three or four years to promote abundant blooms. In early fall, cut back the foliage to about 6 inches and divide the clump into sections, each with 5-6 growth points and adequate roots.

These are some of the easiest to grow, so if you are skeptical of the lovely iris, at least give these a try!