Monday, October 13, 2008

Bearded Iris

Bearded Iris- Bold and Beautiful
by Kim Willis

Bearded Iris, sometimes referred to as German iris, have some of the most colorful flowers, [as well as colorful names], in the garden. Bearded Iris are hardy and easy to grow and good for beginning gardeners. Bearded Iris are also a collectors delight, with hundreds of varieties on the market. For a splash of color in late spring and early summer, plant some Bearded Iris in your garden.

Bearded Iris have thick, “sword- like” leaves. The Bearded Iris flower has six petals. Three petals stand upright and these are called the “standards.” The other three petals droop downward and are called the “falls.” Each “fall” has a group of hair-like growths near its base called the “beard.” Each Bearded Iris can be all one color- beard, falls and standards, or each part can be a different color. The flowers appear at the end of long stalks in clusters. Some varieties are fragrant. Bearded Iris begins blooming in mid spring with the dwarf and intermediate varieties, and continues into early summer with the border and tall varieties. Some new varieties may re-bloom in fall when the season is long and mild.

Growing Bearded Iris

Bearded Iris are hardy from zone 3-9. The best time to plant Bearded Iris is late summer or early fall. Bearded Iris may be sold in pots or more commonly, as bare rhizomes. A rhizome is a long, fleshy looking thing with roots coming out of the bottom. It will generally have a few leaves, called a fan, that have been cut to 3-4 inches. Don’t worry if the fan is dry and yellow, as long as the rhizome is firm and plump. Mushy, soft, or shriveled, dry rhizomes, or those with holes in them should not be bought. Long, branching iris rhizomes with two or more fans will give you bigger plants and are more likely to bloom the first year. About 60-70% of Bearded Iris bloom the first year after they are planted.

Bearded Iris need full sun. They need well drained soil, and do well with little water after they are established. Iris benefits from a small amount of low nitrogen fertilizer in early spring as growth starts. For the best chance of getting re-blooming varieties to actually re-bloom, fertilize them again after the first bloom has finished, and give them a little water if the summer is dry.

To plant Bearded Iris rhizomes dig a trench a few inches deep and make a little mound of soil in it. Place the rhizome on the center of the mound and fan any roots out along the sides of the mound. Then re-fill the trench. The top of the rhizome should be just barely covered in soil. In heavy clay soil the top of the rhizome can even be left exposed. Bearded Iris will not bloom if they are planted too deeply. Plant the rhizomes 18-24” apart. The first year after planting the Bearded Iris rhizomes should be mulched with straw, oak leaves or other material that doesn’t mat down. This is to prevent them from being heaved out of the ground before the roots are established. Remove the mulch as soon as the weather begins to warm. Bearded Iris should be kept weed free and they are one plant that should not be mulched. The tops of the rhizomes need air and sun for the plants to do well.

To keep your Bearded Iris plants looking their best remove each flower as it dies. When all the flowers on a stalk are finished blooming cut the stalk down as close to the base of the plant as possible. Remove any leaves that yellow or have spots and streaks on them, and cut all the leaves off close to the ground after frost in the fall. This helps keep disease and pests from over-wintering.

Bearded Iris needs to be divided every 3-4 years for best bloom. Over time the center of the clump stops blooming and if the plants are too crowded, all may stop blooming. Dig up the clumps after they have bloomed, wash off the rhizomes and cut apart the clumps. Leave a nice section of firm rhizome with a “fan” or two. Cut the leaves on the fan back to a couple of inches. Discard the old, woody and dry looking pieces of rhizomes from the center of the clump and also discard any soft, black mushy pieces or rhizomes with holes bored in them. Then re-plant your divided rhizomes and share the excess with other gardeners.

In some areas Bearded Iris may get Iris Borer. A night feeding moth lays eggs on the plants near the leaf base. These hatch into caterpillars which first feed on the leaves, then move into the rhizomes. They are big, fat pink things that eat the inside of the rhizome. This leaves the rhizomes more susceptible to bacterial rot, which turns the rhizomes black and mushy. To keep Iris plants healthy remove damaged and diseased rhizomes, cut back and remove leaves before winter, and don’t over water.

Choosing Varieties.

The iris family contains many species, the Bearded Iris we grow in our gardens are hybrids of some of those species. There are hundreds of varieties of Bearded Iris with names as colorful as their flowers. In catalogs they are generally grouped by height, flower size and bloom time. There are varieties of Bearded Iris that grow only 6” tall and others that grow 3’ or higher. I am not going to list specific names, as there are so many.

Using Bearded Iris

Bearded Iris are usually grown as part of mixed borders. Small varieties can be grown in rock gardens or even in pots. Pots should be sunk into the ground to over winter in cold areas.
The rhizomes of iris are dried and powdered to form orris root and dried rhizomes are also used to make perfumes.

copyright Kim Willis 2008


Birch Trees- Beautiful Bark, No Bite
By Kim Willis

Birch trees have been long been a popular landscape choice. There are species of birch growing throughout North America, Europe and temperate Asia. Birch trees have a graceful shape, interesting bark and good fall color. They are not the best choice for all landscapes but if the conditions are suitable, there are few trees prettier than a birch.

North Americans tend to think of birches as clumps of small trees with white peeling bark. These clumps were widely planted as landscape trees before the arrival of the Bronze Birch Borer. This destructive beetle attacks and kills many types of birch trees, but white barked birches from Europe are the most susceptible. However, there are many types of birch and some are very resistant to borers and are seldom attacked if they are healthy.

Birch trees are generally small, 20-30 foot and pyramidal in shape. There are some weeping varieties. Birch leaves are thick, glossy, dark green in a rough triangle shape. There are some cultivated varieties with purple or reddish leaves. Birch leaves are lighter on the reverse side, have serrated edges, and are arranged alternately. Some varieties have deeply lobed leaves with a lacy appearance. Fall color of birches is generally a good, clear yellow. Birch trees have both male and female flowers, the male flowers are long, dangling and generally in clusters of threes. The female flowers are much smaller and rounder. The pollen of birch trees is highly allergenic to people with seasonal allergies.

The bark of birch trees is the reason many are planted as landscape trees. When young most birch trees have brown bark but as some age they may get various shades of white, yellow, or red bark that peels and curls, revealing contrasting colors beneath it.

Birch grows easily from seed but most gardeners will start with small trees. Birch trees are best planted in early spring. If you want a clump of birch trees you can buy several small trees and plant them in the same hole or you can buy trees in pots which have several stems.

Birches are trees of the forest edge and riverbanks. They like cool shaded soil at their feet and their heads in the sun. Most birches prefer cooler climates, from zone 3 to zone 6, but there are a few species that tolerate warmer zones. Birch trees have shallow root systems and don’t do well in dry areas. They do not do well in alkaline soil, [a ph of 6.5], or higher, so a soil test before planting birch trees may save time and money. Good places to plant birches are the north and east side of homes or out buildings, windbreaks or tree lines. Birches should be planted where they can be watered during dry periods. Although they need moisture, most birches will not thrive where the soil is always wet. The River Birch is a little more tolerant of wet conditions. Don’t plant birch trees where they will have to be frequently pruned, birch bleeds profusely when pruned and the wounds attract the Bronze Birch Borer. Prune birch trees only during the time they are dormant. If the trees are damaged during the growing season apply a registered insecticide; not tree paint, to the cut surface. Keep children from peeling away large areas of bark, they hear many stories about birch bark and often want to experiment. This may damage the tree or attract insects.

Mulch birch trees after planting with about 3 inches of organic mulch to conserve moisture and cool the soil. Birch trees should not be planted where salt used on sidewalks or roads in winter will run off around the root system. Birch trees are not good trees for parking lots or other areas where they are surrounded by pavement.

Birch trees also attract an insect called a leaf miner. This insect lays eggs in tiny slits on the leaf surface and the larvae that hatch tunnel between the two leaf surfaces. The leaf turns brown and falls off. While leaf miners don’t kill the trees, they make them look very unsightly and may weaken a stressed tree even further. Using systemic insecticides can control both the Bronze Birch Borer and leaf miners. Homeowners have several products that they can use. Contact your local County Extension Service for their recommendations in your area.

Choosing Varieties

Varieties with white bark are more susceptible to Bronze Birch Borer but these varieties have been bred to be resistant, ‘Whitespires’, ‘Renaissance Reflections’, ‘Rocky Mountain Splendor’. River birch, Betula nigra, is tolerant of heat and wet conditions and somewhat resistant to borers. ‘Heritage’ is a selection of river birch that is even more resistant. River birches have light gray bark, peeling to show white, pink, and brown underneath. ‘Summer Cascade’ is a weeping birch reaching about 10 foot tall, ‘Filigree Lace’ is a cut leaved dwarf birch, ’Royal Frost’ is borer resistant and has burgundy foliage until fall, when it becomes orange. Betula lenta, Sweet Birch, has smooth mahogany red bark that does not peel, and its leaves have a clean, pleasant scent.

Using Birch

In the right place the birch is a lovely tree, with good fall color and interesting bark in the winter. It provides light shade for plants like hosta and ferns and likes their company at its feet. Many species of butterfly larvae eat the leaves of birch.

Birch trees had many uses by indigenous people. They were used in religious and magical rites, and birch bark was used for some of the earliest writings. The bark is full of oils that help preserve it and many artifacts hundreds of years old made with birch bark have been recovered. Besides the famed canoes, birch bark was used for roofing, native houses, baskets and bowls, paper, and even clothing. The oily wood is excellent for fire starting. The sap of some types of birches is boiled into syrup like maple syrup and also made into wine and vinegar. The small nutlike seeds were also used as food.

Copyright Kim Willis 2008


Astilbe- An Astonishing Perennial for Shade
By Kim Willis

If you need color in a semi-shady spot in summer and early fall then Astilbe is a plant you will want to get to know. Astilbe, sometimes called False Spirea, will lend its airy graceful flowers and bring those dull spots to life. Astilbe has few disease or insect problems and is resistant to deer and other animals. Astilbe also attracts butterflies.

Astilbe will grow well in zones 4-8. There are several native Asian species from which our cultivated varieties were developed. Some varieties have dark green leaves, some have a maroon tint to the leaves and stems and some are a lighter green. There is at least one variety that has burgundy-purple leaves. The leaves are compound, with serrated edges, and somewhat fern like. New leaves are glossy, but this fades as the season progresses. Some astilbe plants have good fall colors of yellow and orange also. Astilbe plants form mounding clumps, slowly increasing in size each year if they are happy. The height of the plants, including flower spikes, ranges from 10 inches to 4 foot or more high.

Astilbe has tiny flowers all packed close together in plumes. The plumes are at the top of the plant, above the foliage. Some flower plumes are upright, thick clusters and some are narrow and gracefully arching. Astilbe flower colors range from lavender to all shades of red, pink and white. The flower plumes are long lasting and dry nicely for arrangements.

Growing Astilbe

Astilbe is generally purchased as a bare root or potted plant. They are hardy and can be planted outside as soon as the soil can be worked. If you can, work lots of compost, sphagnum peat, aged manure or other organic material into the soil before planting. Astilbe will grow in part shade or even in full sun if kept moist. It will survive in deeper shade but will not bloom as well. They prefer loose, fertile soil but the primary key to their success is plentiful moisture. While astilbe will grow in shade, their shallow root systems have a hard time competing with tree roots for moisture. If lacking water astilbe will dry up and go dormant or die.

When growth begins in the spring fertilize astilbe with a general purpose, slow release fertilizer. Check to make sure the roots of the plant are not exposed, as the shallow roots are prone to being heaved out of the ground over winter. If they are, gently dig under them and settle them back into the soil. Keep astilbe watered well if the weather is dry and they should reward you with beautiful color. By selecting different varieties you can have astilbe in bloom from late June through September. You can deadhead them if you like or allow the plumes to dry on the plant. After a hard frost has killed the leaves, trim off dead leaves and stems and lightly mulch with oak leaves or pine needles to help prevent astilbe from being heaved out of the ground.

If your plants are doing well the clumps should increase, and they will need to be divided every 3-4 years. Dig up the plant in early spring and divide the clump into several pieces with a sharp knife. Replant immediately and water well. Extra plants can be potted to share with friends.

Choosing Varieties

‘Rheinland’ is bright pink, upright and early blooming, ‘Spinall’ has airy upright plumes of bright red and reddish foliage, ‘Ostrich Plume’ has tall, pink drooping plumes, ‘White Gloria’ has thick white plumes in mid summer, ‘Bridal Veil’ has later, tall white plumes, ‘Taqueti’ hybrids are tall, in lavender pink shades for late summer, ‘Pumila’ is a short lavender spiked variety good as a groundcover. ‘Sprite’ is shell pink with arching flower sprays, ‘Lollypop’ is bright pink with bronze foliage, ‘’Visions has short compact spikes of purple and is said to have a soft, pleasant scent, ‘Sister Theresa’ is a salmon pink that is also scented. ‘Red Sentinel’ has fire red, compact plumes. ‘Color Flash’ has interesting foliage in burgundy and purple with soft pink plumes. ‘Finale’ is one of the latest to bloom with drooping, soft rose plumes.

Using Astilbe

Astilbe looks good in masses of one color or mixed with perennials such as hosta that also appreciate moisture. Astilbe can furnish the shade at the feet of lilies and also mixes well with daylilies. It is good in butterfly gardens that receive some shade or in naturalized gardens that need a splash of color. Astilbe makes a good cut flower and is sometimes forced in pots for winter bloom. Astilbe flowers also dry well.

Copyright Kim Willis 2008


Perennial Asters- Stars of the Fall Garden.
by Kim Willis

There are two types of plants called asters, in this article we are discussing the perennial asters and will leave annual or China asters for another article. Perennial asters are tough, hardy plants that provide beautiful fall color. Asters are easier to grow than mums are and more likely to survive the winter even when planted in full bloom in the fall. There are many varieties of asters that will suit any sunny garden, from formal to naturalized.

Perennial asters grow around the world, in all kinds of climates, and there are many North American native species. Recently the North American species of aster were re-classified and actually taken out of the aster family. We won’t worry about the taxonomic mess here; we will simply refer to them as asters. Aster comes from the Greek word for star, and asters may be seem as numerous as stars sparkling across a dry meadow. They are an important source of late summer and fall food for butterflies and bees.

Native asters are often tall and gangly; they have struggled up through tall grass and weeds to the sunlight. They throw their froth of small daisy like flowers out above the brush and sprinkle them through the weeds. Cultivated varieties of aster are more compact and have a mounding habit. I happen to like the way the native asters wind their way through other plants and allow the asters in my borders to behave the same way.

Asters have thick woody stems and long narrow leaves. Almost all asters are upright plants; there are some that hug the ground and one that is a climbing vine. Aster flowers are small, about an inch across, and daisy like. They come in all shades of blue, purple, white, pink and red. While the centers are often yellow, there are no yellow or orange perennial asters yet. Asters begin blooming in late summer and usually continue blooming until a hard freeze kills them.

Growing Asters

There are perennial asters hardy from zone 3-9. Asters tolerate a wide range of soils. They will do well in dry areas but will also do fine in well-watered sites, although they may be more prone to powdery mildew, a fungal disease. Most asters prefer full sun; some will tolerate light shade. Unless your soil is extremely poor, native species of asters do not need fertilization. Some of the cultivated varieties may bloom heavier if they are fertilized in the early spring with a timed-release fertilizer for flowers.

You can start asters from seed but most gardeners will want to start with plants. If you start with seeds you can sow the seed where you want the plants to grow or for best results, you can start the seed indoors 6-8 weeks before your last frost and transplant outside.

Asters form large clumps and need to be divided every 3 years or so. Simply dig up the clump in the early spring and separate it into 2 or 3 parts, which you will then re- plant. Space asters from a foot to 3 foot apart, depending on variety.

If you want dense rounded clumps and abundant flowers, pinch your aster plant back by about 6 inches at the beginning of July. Don’t cut back after July 15 though. If you don’t pinch back your asters they will be taller and the display will be airy and lighter. In the fall after a hard freeze has killed the plants, they may be cut off to ground level.

Some people choose to move wild aster plants into the garden. Take only plants from your own property or from areas where you have permission to dig the plants. Individual plants have different growth habits so choose carefully. It might be best to choose the plant in the fall when it is in bloom, mark the plant, and return in the spring to transplant it, as they seem to establish better when moved in the spring.

Choosing Varieties

The native New England Aster has lovely blue-purple flowers. Cultivated varieties of this native include “Purple Dome’ - deeper purple flowers on a rounded, compact plant, and ‘Alma Potschke’ - rosy pink flowers. White Wood Aster is a native species that has loads of tiny white flowers with purple centers. It will tolerate light shade. The native climbing aster, Carolina Aster, is hardy only to zone 7. It has light pink flowers with a light pleasant scent. Other asters include ‘Lady in Black’ which has deep purple foliage and hundred of tiny white daisies with pink centers, ‘October Skies’ - a bright blue flowered plant only 18 inches high and excellent as a groundcover and ‘Alert‘ a dwarf aster with red flowers. Silky Aster is a native that has silvery gray leaves and rose-violet flowers. ‘Wonder of Staffa’ has lavender flowers that begin in late June and keep blooming until frost. ‘Pink Star’ is a 2 foot mound smothered with small, soft pink flowers. ‘Nanus’ is a tiny plant, 12 inches, with shiny green leaves and sky blue flowers.

Using Asters

Asters are excellent for fall color in borders. Native species are wonderful for naturalized gardens and attract butterflies and bees. Some aster varieties make a colorful groundcover for sunny, dry areas. Compact varieties are excellent for fall containers. Asters make good, long lasting cut flowers and also dry well.
Copyright Kim Willis 2008