Dr. Leonard Perry, Extension Professor
University of Vermont

Witchhazels are landscape shrubs deserving of wider use, attractive for their nice habit, fall foliage and long-blooming fragrant flowers.  In fact, they are the earliest and latest shrubs to flower during the season.   While the native species is the most hardy, its yellow-orange fall flowers are not as attractive as those with more colorful yellow, orange or red flowers in spring.  They’re easy to grow, require little maintenance, and have few if any pests and problems.

If you haven’t heard of these shrubs, you may have heard of the medicinal products made from them now, and originally by Native Americans.  The extract from leaves and bark is used for sores and bruises.  The distilled oil is used in skin care products for a range of purposes, from aftershave to skin ailments such as psoriasis and eczema, to insect bites and poison ivy rashes.  You will find it in many hemorrhoid preparations too.

This genus (Hamamelis) is the main member of the Witchhazel family.  The name comes from an Old English word for pliant or bendable branches.  Or the “witch” may be related to the centuries old use of stems as divining rods in dowsing for water.  They’re not closely related to the true hazels (Corylus) that bear the nuts of the same name.

Witchhazels are deeply rooted, multi-stemmed shrubs with a rounded to irregular upright growth habit.  They often have an attractive branching structure.  These medium to large shrubs reach 6 to 12 feet high or more.  They spread (they’re not aggressive spreaders) to eventually form large clumps 12 to 15 feet across.  Leaves are rounded to elongated, 2 to 5 inches long.  Flowers are rather unique, consisting of four narrow, strap-like petals under an inch long, in various colors and often twisted.  Blooms appear either in spring or fall, depending on selection, and last 4 weeks or more.  They have an elusive fruity to spicy fragrance.

In nature, witchhazels grow along the edges of woods, so are fine in part shade (4 to 6 hours of direct sun a day).  They will grow in full sun as well, where they’ll be more dense, rounded, and with more flowers.  They won’t grow well in deep shade.

Although adaptable to a range of soils, they don’t grow well in ones that are too wet or prone to dry out frequently.  Add lots of peat moss or organic matter when planting.  Water well and deeply when the top 2 inches of soil dries out, particularly in the first two years after planting.  Fertilize with product of your choice each spring, or simply top dress around plants with an inch of compost.

Witchhazels are good choices for naturalistic landscapes with plants such as viburnums, winterberries, redosier dogwood, serviceberries, or foamflowers underneath.  They make a nice contrast to evergreen shrubs.  Being large, consider them for backs of borders, or used singly as accent plants.  In sun, where they become dense, they make good screens or informal hedges.  If you want to enjoy the subtle fragrance and beauty of the flowers, plant witchhazels near walks or patios.  If used near buildings, make sure they’ll have enough room to grow over time.

Cut branches of witchhazels during late winter to “force” into bloom indoors in one to two weeks.  Place the base of branches in warm water, changing the water every day or two.  Keep them in a cool area, out of sun, with a clear bag over branches until flowering to keep the humidity high.  If branches are already beginning to bloom when cut, place in warm water containing flower preservative (from floral shops).  These are often best used in simple or Japanese-style arrangements.

The native common witchhazel (H. virginiana) has yellow flowers in October when the golden leaves begin falling, so are really only seen once all leaves are off.   ‘Harvest Moon’ is a selection from breeder Richard Jaynes of Connecticut, with lemon-yellow flowers that appear a couple weeks later, once leaves have fallen, so are better appreciated.  Flowers of this eastern U.S. native are hardy through USDA zone 4 (to -30 degrees F).  This plant can become one of the largest in this genus, reaching 20 feet tall and wide with an open, spreading habit.

The vernal witchhazel (H. vernalis), native to the Midwest and South, is very early spring blooming with a pungent fragrance.  The yellow to red-orange flower petals, about a half- inch long, appear before the leaves which have a reddish cast as they unfold.    These are slightly less hardy than those of the common witchhazel, but still through much of USDA zone 4. You may find the cultivars ‘Autumn Embers’ with orange flowers or the yellow ‘Sandra’.

Chinese witchhazel (H. mollis) is less hardy, being marginal in USDA zone 5 with flowers damaged at -10 to -15 degrees (F).  It and its cultivars have flowers in varying degrees of yellow to gold.  Japanese witchhazel (H. japonica) is similar to the Chinese, with similar hardiness, but with less showy and less fragrant flowers and is less commonly found.

Most commonly found are the hybrids (H. x intermedia) between the Chinese and Japanese, with more vigor than either.  Upright and spreading with time, they are usually 12 to 15 feet high and wide, but could grow even larger.  They often flower into USDA zone 5 in the north in early spring, as their parents, with their flowers hardy to about -20 degrees.   There are many cultivars of the hybrid witchhazel, ‘Pallida’ with its sulfur yellow flowers being one of the best.  ‘Diane’ has orange red flowers, while ‘Jelena’ has coppery orange flowers and orange red fall foliage. ‘Arnold Promise’, originally named in 1963 at the Arnold Arboretum in Boston, has yellow flowers arising out of a red cup (“calyx”). It is one of the best and most popular.

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Caring for Cut Tulips

Dr. Leonard Perry, Extension Professor
University of Vermont

Although the outdoor landscape may be bleak right now, the greenhouse industry has found a way to bring spring into our homes.  And that’s by fooling tulips and other spring flowers into blooming early indoors.          When properly cared for, cut tulips will stay fresh in a vase of water for seven to ten days.

The cut tulips you find at your florist shop, local greenhouse, and supermarket this time of year are “forced” tulips that were grown in greenhouses in the United States or as far away as the Netherlands.  Growers have used special temperature treatments to confuse the biological clocks of the flowers and force them to bloom on a different schedule than they would if grown outdoors.  It allows them to produce flowers of uniform height and quality for sale during winter months. This is similar to the method you can use at home with potted tulips, placing them at around 40 degrees (F) in fall for at least 10 to 12 weeks before bringing back into warmth.

For long-lasting tulips, buy ones very “tight” or unopened, with buds still green and just showing some color. Recut the stems when you first get them home.  Lay the bouquet on its wrapping paper or newspaper, or over a sink, and cut the stems diagonally using a sharp knife or scissors, removing about one-half inch of stem.

Place the stems directly in the vase, or if holding for a while just in water, recut the stems before placing in the final vase.  Many recommend cutting stems under water or under running water, so no air enters the stems to block the water vessels there. Make sure the vase is clean before using.

Fill the vase with lukewarm water, not ice cold, which is taken up better by the stems.  Use a floral preservative— a powdery mix of plant food and bacteria inhibitors– available at all floral shops, and often coming with the bouquet you buy in stores.

Although many people believe that adding a dash of carbonated lemon-lime soft drink, a teaspoon of sugar, a penny, or even a bit of bleach to the water will help extend the life of the flowers, none of these folk remedies are as effective as commercial cut flower food. While some say that a preservative is not needed for cut tulips, a study published in 2012 (Kumar and others, Journal of Applied Horticulture) showed that any of 10 different preservatives kept flowers longer than if just in water.

The general rule of thumb for arranging flowers is that the bouquet should be about one and one-half times the height of the vase.  Tulips work well in tall, straight vases, although they can be arranged in a fan shape in a low, wide bowl.  For the latter you will need to keep the flowers in place, anchoring with a florist “frog” or block of florist foam, these held to the bottom of the vase to support the arrangement. Don’t mix tulips with cut daffodils, as the latter exude a sap that clogs the water uptake of other flowers.

Make sure and check the water level daily, as tulips use much water, and for longest life you don’t want the vase to dry out.  Place the bouquet out of direct sun, and away from heating vents or drafts.  Top off the water level daily to keep the arrangement fresh, and replace every 3 to 4 days or when it becomes cloudy.

An interesting fact about tulips is that they continue to grow after being cut, up to an inch or more.  They are “phototropic”, bending towards the light, so rotate containers daily to keep stems more upright.

Want to buy some cut tulips for Valentine’s Day, but not sure about the color?  Then consider these facts from a research study published in 2010 on color preferences (by Yue and Behe in the HortScience journal).  Both men and women chose a red or bronze color most often then, followed by a peach or pink color.  This makes sense, since red is considered a color to express love.  Yellow was the least chosen color then, as well as overall through the year.

Of buyers of cut flowers through the year, 70 percent were women and 30 percent men.  Women bought 44 percent of cut flowers for themselves, 56 percent for gifts with only 6 percent bought on Valentine’s Day.  Only 6 percent of purchases by men of cut flowers through the year were for themselves, 96 percent bought for gifts, with 23 percent of their yearly purchases on Valentine’s Day.

While cut tulips are a lower cost flower gift for Valentine’s Day giving, and make great gifts through the winter and into spring too, you may find tulips planted in pots.  If buying these, similar to the cut tulips, buy with buds still unopened, and keep in cooler temperatures for longest life.  Since most tulips are not perennial, they likely won’t rebloom in future years if planted outdoors in spring.

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Wood Ashes in Gardens

Dr. Leonard Perry, Extension Professor
University of Vermont

Winter in the north means wood ashes, even more in recent years with the higher cost of heating oil and many homes converting to wood stoves or wood pellets.  Rather than sending the wood ashes that are left to the landfill, they can be used “judiciously” in landscapes and gardens.

The main benefit of wood ash in the soil is to raise the soil pH, or make it less acid.  Soil pH is a measure of acidity on a 14 point scale, with 7 being neutral.  Below 7 is acid, and above is alkaline.  Most our northeast soils tend to be acidic, often 5.5 to 7.  Slightly acidic is ideal for many plants, as this is the range in which most nutrients are available to them.  Generally, wood ash is from 25 to 45 percent calcium carbonate, a common liming agent, so you can use twice as many ashes as you would this lime.

So what this means for wood ashes is that if your soil is 6.5 to 7 or above, don’t add them.  If you’re not sure of your soil pH, do a soil test in spring when the ground thaws (kits are available from your local Extension office and many garden stores), but in the meantime go lightly on the wood ashes.  Adding too much may do more harm than good, particularly since wood ashes change the soil pH much more quickly than most liming products.

Keep in mind a plant or crop’s preference for soil acidity, and so wood ashes.  Asparagus, conifers, and juniper tolerate more alkalinity, and so wood ashes.  Potatoes, blueberries, and rhododendrons prefer a fairly acidic soil (less than 5.5), so don’t add any wood ashes for these or where they’ll be grown.

When wood burns, it gives off nitrogen and sulfur as gases, but leaves behind other plant nutrients in small amounts.  Hardwoods such as maple and oak provide up to 3 times as much ash, up to a third more calcium, and slightly more nutrients, than softwoods such as fir and pine.  The main nutrient added is potassium (the third number on fertilizer bag analyses), perhaps up to 10 percent “potash.”

Adding wood ashes to plants is not a new practice, being first documented centuries ago by the Romans.  Its benefits became widespread in this country in the 18th century when the method was discovered for making potash– potassium bicarbonate– from wood ashes.  In fact, this method of basically soaking ashes in a pot received the very first U.S. patent in 1790.

Although the amount to add will vary with soil and crop, a good rule is 20 pounds (roughly a 5 gallon pail) per 1000 square feet of garden.  This is the amount you may get from one cord of firewood. You also may see recommended ashes “topdressed” or spread evenly up to one half inch thick. Tomatoes in particular like potassium, and so wood ashes.  For lawns, go a bit lighter—10 to 15 pounds per 1000 square feet.  For individual plants, spread one-half to one pound of ashes evenly around a mature shrub or rose bush.  For trees such as apples, you can spread around them up to an inch thick.

Clay soils usually tolerate more wood ashes than sandy soils.  Don’t leave the ashes in piles or clumps, as concentrated nutrient salts can leach from these and damage roots. It’s best to spread them in winter or early spring, a month or so before planting or adding other fertilizer.  This gives the ash time to fully work, and not interact adversely with some nitrogen fertilizers.

Since wood ash is about a 0-1-3 analysis (nitrogen-phosphorus-potassium), and many soils contain sufficient phosphorus already, perhaps the only additional nutrient you may need to add is a source of nitrogen.  But a professional soil test will recommend any additional fertilizer.

Wood ashes also can be added to compost piles to keep the acidity more neutral.  Sprinkle some on each layer of compost as you build the pile.  If stockpiling wood ashes to use later, keep them dry.  Rain will leach the nutrients, and so benefit, from them. If storing, use a metal can so any hot coals in the fresh ash wont cause a fire.

Another option is to store wood ashes dry, then make a “tea” with them during the growing season for watering plants and so providing some nutrition.  Put about 3 pounds in a permeable bag or wrapped in burlap into a 30-gallon garbage can of water, leaving it there for at least 4 or 5 days.

When dry, wood ashes can be spread around perennials such as hostas to physically deter slugs and snails (they don’t like to cross dry ashes).  But when they get wet they lose this effectiveness, so you would need to reapply.  If done too often, this could end up adding too many ashes and so too high levels of salts in the soil.

It probably seems obvious, but bears mention, that ashes from burning trash or treated wood shouldn’t be used on gardens. They may contain chemicals, or elements in high amounts, toxic to plants. Since wood pellets are made from sawdust or wood particles held together with natural lignins from the wood when heated in the molding process, they’re fine to use.

So this winter as you snuggle by a wood stove or fireplace, or see a neighbor burning wood but who doesn’t garden, consider recycling the ashes from this natural product back to the soil.  Just make sure to not use too much, and avoid spreading around acid-loving plants.  If your soil is already fertile or of the correct pH, wood ashes can be used to hide stains on paving, melt ice on walks, make soap, shine silver, or even neutralize skunk odor on pets.

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The History of Holiday Greens

Dr. Leonard Perry, Extension Professor
University of Vermont

Many people usher in the holiday season by decorating their homes with evergreen boughs, sprigs of holly, garlands, and mistletoe.  Although now considered a Christmas tradition, Vermont writer Lisa Halvorsen explains how this practice is not something recent, dating back many centuries.

The Greeks and Romans were among the first to bring evergreen boughs indoors in winter.  They were amazed that the evergreen remained green year-round, even during the bleak winter months, and decided that it must have supernatural powers.  To them it symbolized nature and the promise of spring when the earth would be verdant again.

In the 1800s, greens were used in this country to make memorials to honor loved ones who had died.  Evergreen boughs and other greens were woven into wreaths, crosses, and stars and placed on graves in cemeteries. During the Victorian era, the custom of bringing evergreen boughs and other greens into the house at Christmastime was revived.  Many people made elaborate arrangements for mantelpieces and tables using boughs, ivy, laurel, yew, and hemlock.

A kiss under the mistletoe, another popular American custom, came from Scandinavia, where according to mythology, Balder, the son of Frigga, the Norse goddess of love, was struck dead by an arrow made of mistletoe.  As Frigga wept, her tears fell onto the mistletoe and turned into small, white berries.  She declared that mistletoe should no longer be used to kill, but to encourage love.  Thus, anyone found standing beneath the mistletoe must be kissed.

Mistletoe also played an important role in the Druid celebrations of the winter solstice.  Because it appeared to grow in the air–the plant wound itself around the tree, its roots never touching the soil–the Druid high priests believed that it was a sacred plant.  During the solstice, they would climb the trees, cut down the mistletoe, and toss it to the crowd below.  It was considered bad luck if even a single sprig touched the ground.  Catching the mistletoe ensured that livestock would be fertile and reproduce.

Holly and ivy often are used together in holiday decorations, a tradition that stems from a Middle Ages belief that holly was male and ivy female, and so the two should be intertwined forever.  Holly also was thought to have protective powers, while ivy stood for love.

The tradition of decorating evergreen trees for the holidays began with Martin Luther in the early 1500s.  Legend has it that he was walking through the woods one Christmas Eve and noticed how the sparkly stars shone through the branches of a snow-covered fir.  Wanting to share the magic with his children, he chopped down the tree and brought it home.  He decorated it with candles to represent the stars.

In the 1600s, families in France decorated fir trees with gold foil, paper roses, apples, and sweet treats at Christmastime.  German immigrants brought this same tradition with them when they settled in America.  However, Christmas trees did not become widespread in America until the 1800s.  Although first sold commercially in New York City in 1851, it wasn’t until four years later, when President Franklin Pierce placed the first tree in the White House, that many Americans adopted the tradition.  Electric Christmas tree lights were invented in 1882 by Edward Johnson, Thomas Alva Edison’s assistant.

This year, as you deck your halls with holiday greens, think of the history behind these traditions and of the many before you who incorporated greens into their rituals and celebrations.

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Cleaning Garden Tools

Dr. Leonard Perry, Extension Professor
University of Vermont

Cleaning your garden tools regularly after use is ideal, but at the least they should be cleaned before putting them away for winter.  Clean tools work more effectively, so are easier to use, and they last longer.

Keeping blades sharp improves cutting, which is easier on you and the plants.  Keeping tools used in soil cleaned keeps their edges sharper too, preventing rust from forming, and removes possible disease-laden soil particles.  Cleaning tools even more often when working on infected plants is essential to prevent disease spread.  If pruning diseased limbs from trees, keep a container of rubbing alcohol, bleach (one part to 9 parts water), or disinfectant (such as Lysol) handy to dip blades in between pruning each plant to avoid spreading disease.

For tools such as shovels, hoes and garden forks that are used in soil, wash them after use with a forceful stream of water from the hose.  For stubborn soils such as clay, use a wire-bristle brush or dull implement if needed.   Then dry tools with a rag.  For blades of saws and pruners that end up with sticky plant sap, such as from evergreens (pines, spruces and the like), use some paint thinner to remove the sap before wiping with a rag.

Even after cleaning, the worn metal can rust, even more so if higher grade steel.  To prevent this, wipe tools or spray with a very light coat of motor oil.  Some dilute this with kerosene, 2 parts oil to one of kerosene.  Others recycle their old oil from mowers for this use. You can wipe the oil on with an old rag or paper towel, spray it on with a hand sprayer, or make a mix of the soil with sand to push tools into after each use.  The latter is easy, quick, and the sand helps provide some abrasion to remove soil in the process.  The oil breaks down rapidly in the soil, and little is used, so you shouldn’t have any negative soil effects.

For hand tools, some use a strong black tea.  Brew up enough in a pan or kettle to cover the tools, then let them, or blades at least, soak for a few hours after the tea is cooled.  Rust should wipe off easily with a rag.  If tools aren’t very dirty or rusty, a balled up handful of wax paper rubbed over surfaces may be sufficient—both cleaning and leaving some protective wax on them.

If tools have gotten severely rusted, you may need to use rough sandpaper, and even perhaps a wire bristle brush.  For the most rusted, you may need to use a drill with wire brush attachment.  For the latter in particular, make sure to wear safety glasses. Then make sure to wipe and coat with oil.

Sharpen tools too, at least at the end of the season. Best is to sharpen them regularly as used during the season.  This is more important if tools have rusted.  For dull large tools such as shovels, axes, and spades, you can use a hand file available from hardware or home stores.  If very dull, you may need a high speed grinding stone or drill attachment.  As with cleaning, make sure to wear eye protection if using a high-speed grinder.

If using a grinder made for this purpose, as some do with lawn mower blades, it is easy to get carried away.  If the metal heats up too much it can lose its “temper”, meaning it won’t hold an edge well again.  If grinding, keep the metal from heating by dipping in cold water.  It should remain cool to the touch.  Improper sharpening of mower blades can make them out of balance, which can harm the mower motor as it turns at high speeds.

For finer tools such as pruners and loppers, an oil stone or honing stone is what many gardeners use.  I spend a bit more for a good quality handfile, such as with cut diamond or carbon surface, to make the job go much better and more quickly.

Whatever sharpener you use, follow any directions so they work properly.  If using a stone, slide the blade along the stone in one direction, doing so repeatedly until sharper.  If using a file, such as “mill file” from a hardware store, get one with a handle so you can maneuver it more easily.  Draw the cutting teeth of the blade along the edge of the tool in one direction.  Keep the file at an angle to the edge of the tool surface you’re sharpening.

So how sharp is enough?  Anything of course helps.  Tools such as shovels and hoes don’t need to be as sharp, and pruners should be more sharp.  You can feel the sharpness with fingers (be careful if sharp knives or pruners), or just look at the “bevel” and angle.  The bevel is the sharpened edge, the angle is between the two edges or bevels.  Duller tools have a shorter edge or bevel, and generally wider angle—perhaps 30 degrees between the sides or bevels.  Sharper tools have a longer bevel, and more narrow angle between each side—perhaps 15 degrees or so.

Many tools now have plastic handles, but if you have one with wood, treat it as well for longest life.  Rub wooden handles with a rag, slightly moistened with linseed oil or other wood protection oil product.

Once tools are cleaned and sharpened, store them properly in a closet, garage, or shed out of the weather.  Keeping them off the floor helps prevent any moisture and rust, and dulling.  I like to hang mine by the handles.  If straight handles, I hang upside down with ten-penny nails used to hold the tool itself.  When buying new tools consider stainless steel ones, if available, that are easier to keep clean.

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New England Asters

Dr. Leonard Perry, Extension Professor
University of Vermont

Asters are a hardy, easy-to-grow and colorful group of fall-blooming perennials. New England asters are tall perennials that not only are hardy and low maintenance, but also provide vibrant displays of reds, pinks, purples and white in the fall. At a time when most other perennials have finished blooming, asters provide needed flowers for bees, butterflies, and other pollinators. They combine well with ornamental grasses, rudbeckia, and coneflowers.

Although this species of aster is termed “New England”, it is native to most areas of the eastern U.S., except some southern states. It is hardy in U.S.D.A zones 4 (minimum temperatures in the -20’s in winter) to 8. You can find it planted and growing well even in many western states. Plants generally grow 4 to 6 feet tall, but can be lower, and 3 to 4 feet wide.

In the wild, New England aster is typically found in areas with moist soils, although many have escaped from gardens and naturalized in fields and along roads. It will tolerate clay soils, and some drought once established. Growing in moist soils makes this plant a good candidate for rain gardens, in addition to borders and naturalistic gardens.

New England aster really needs full sun (6 or more hours a day of direct sun) to grow and bloom well. Depending on area, blooms begin in August or September (usual in the north), last for several weeks, and colors vary with the cultivar (cultivated variety). If you want to have even later blooms on some plants or prolong the bloom season, cut some plants back in June by about one-half to one-third. This will make them bushy, shorter, and bloom several weeks later.

There are few serious pests or problems on New England asters. They can get a rust disease, with small rust-colored raised spots on leaves. In some areas, some cultivars may get a white powdery mildew on leaves. Both of these are mostly an aesthetic disease, and plants should grow and bloom yearly in spite of such problems.

Although various common pests may be found on New England asters, as with the diseases, seldom if ever are these a serious problem. Two of the more common, that cause pale leaves with a stippled appearance, are spider mites and lace bugs.

Since New England asters are vigorous growers, some cultivars may need staking. This is particularly the case in rich soils that cause abundant growth, or in part shade. For such plants and conditions, pruning plants back in June as noted for the later blooms will keep them stockier with no need to stake. Especially in areas with longer growing seasons, you may need to cut off spent flower heads after bloom to prevent them from forming seeds that self-sow, if this could be a problem in managed landscapes.

If plants have fewer blooms and open centers after a few years, they may need dividing in the spring. You can either divide the plant in half, or pieces off from the original with a spade; or dig the whole plant, divide it into sections (an old pruning saw or hatchet work well), and replant.

New England aster is in the aster or composite family— Asteraceae— that of sunflowers, daisies, and similar flowers. The asters all used to be grouped together into one “genus” (Aster), but thanks to recent botanical research they’ve been regrouped with names more suited to botanists than gardeners. So, although the New England aster genus is now changed (Symphyotrichum), the species name has remained the same (novae-angliae).

This species of aster was introduced to England in 1710, and over the years cultivars have been bred there and in Europe, and reintroduced here. Since it and the related New York aster bloom in England around the time of St. Michaelmas day (September 29), these may be seen in some references and catalogs as Michaelmas daisies.

In perennial trials at the Chicago Botanic Gardens, 119 asters were evaluated over six years. This evaluation included many other aster species and cultivars beside just those of the New England aster, of which there were 12 cultivars in addition to the native species.

Although none of the New England asters were among the few excellent rated asters in the Chicago trials, two popular pink cultivars rated good, with four stars. ‘Harrington’s Pink’ has rosy-pink flowers mid-season from early September to mid October. It, and other cultivars mentioned, unless noted otherwise, had excellent flowering. In these trials, ‘Harrington’s Pink’ reached about 5 feet high and about 4 feet wide. It had fair resistance to powdery mildew and excellent resistance to rust, as did the following unless noted otherwise.

The other top cultivar of New England aster was ‘Honeysong Pink’, with deep pink flowers the same time as ‘Harrington’s Pink’. It was about the same height, but under 4 feet wide. Another popular pink cultivar, ‘Alma Potschke’ with it’s cherry-pink flowers, rated fair with three starts. In Chicago it has a long bloom period, from early August to late October. Only reaching about 3 feet high, it spread about 5 feet wide.

For a white cultivar, you might consider the popular ‘Wedding Lace’. Rating fair, it had a long bloom period similar to ‘Alma Potschke’, and excellent rust resistance but poor powdery mildew resistance. It reached a bit over 5 feet high, and a little under 5 feet wide.

There were 3 purple cultivars in the Chicago trials that rated fair. The native species grew a bit over 5 feet high, and 5 feet wide, blooming late—from late September to mid-November. ‘Mrs. S.T. Wright’ had only good, not excellent, flowering and poor powdery mildew resistance. It bloomed over a long period similar to ‘Alma Potschke’, only reaching about 4 feet high and wide. ‘Treasure’ had a similar bloom period to the latter, but reached about 5 feet high and about 3 feet wide. It, too, had poor powdery mildew resistance.

One of the more recent introductions has been ‘Purple Dome’, from the Mt. Cuba Center and gardens in Delaware. It is a popular, violet-purple, low cultivar only growing to about 16 inches high and about 2 feet wide. This makes it a good choice for fronts of borders, along walks, massed, or even containers. It bloomed over two months in Chicago, from early September to early November. ‘Vibrant Dome’ is a bright pink sport of this compact cultivar, not in these trials but popular and available.

‘Purple Dome’ is a good example of how resistance to diseases can vary by site. Often considered to have excellent resistance to powdery mildew, in the Chicago trials this cultivar was only rated as fair.

A popular purple-blue cultivar that rated fair was ‘Barr’s Blue’. It has mid-season flowering, reaching a little under 5 feet high with wider spread. ‘Hella Lacey’ is a popular cultivar with light violet-blue flowers, but it rated poor in the Chicago trials. There it bloomed late, had poor flowering, and very poor powdery mildew resistance. September Ruby or ‘Septemberrubin’ is purple-red, and was the only red cultivar in these trials. With only fair blooming mid-season, and reaching about 4 feet high and wide, it too had very poor powdery mildew resistance.

More on the many other asters, including the similar but generally lower New York asters, as well as other perennial evaluations can be found in the reports from Richard Hawke and his Chicago Botanic Garden trials (www.chicagobotanic.org/research/plant_evaluation).

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Perennials for Late Season Color

Dr. Leonard Perry, Extension Professor
University of Vermont
Resist the temptation to cut all those perennials back in fall just to look tidy and be ready for spring.  Of course you’ll want to cut back any that are unsightly, flopped over (“lodged”), diseased, or lack vigor from summer stresses.  But leave some perennials for their attractive fall foliage colors and seedheads.  Those with seeds provide food for birds in preparation for winter. A few may even provide some late flower color.
For fall interest, lower plants will suffice.  But for winter with its usual snow cover, you’ll want to consider leaving some taller perennials.  Many ornamental grasses are a great late-season choice for either their foliage color or texture, or both.  Some provide seeds to birds, too.
Some choices for blue foliage include a few of these ornamental grasses.  ‘Elijah Blue’ fescue makes a nice bluish mound, under a foot high.  Similar in color and habit, only much larger, mounding 2 feet high and wide, is the blue oat grass (Helictotrichon).  More upright and open in habit, its bluish summer leaves turning quite tan in late fall, is little bluestem (Schizachyrium) and its cultivars (cultivated varieties).  Another good low choice, other than grasses but still with narrow leaves, is the pinks or dianthus.
For a more upright effect, consider some of the switchgrasses (Panicum) with bluish leaves, such as the tall ‘Cloud Nine’ (6 feet or more tall), a bit shorter ‘Dallas Blues’ or ‘Prairie Sky’, or even shorter (4 to 5 feet tall) ‘Dewey Blue’ or ‘Heavy Metal’.  Seeds of switchgrasses are attractive to small birds. Results of my trials in Vermont on both little bluestem and switchgrasses, as part of a larger national trial program, are online (perrysperennials.info).
Don’t overlook the blue and purple flowers of the late-blooming New England aster.  If you prune these back by a third to half in June, they’ll be more branched, dense, and will bloom even later into the fall.
Contrasting nicely with bluish colors are plants with burgundy to purple leaves.  Once again there are some 3 to 5-foot high switchgrasses to chose from, the best including Ruby Ribbons and ‘Hanse Herms’.  Several others have some red leaves mixed among the green.  In trials of little bluestem grass cultivars in Vermont, a new one from Minnesota— Blue Heaven— has very attractive dark red fall color on plants just over 2 feet high. 
There are several 4 to 5-foot high cultivars of dark purple-leaved bugbanes (Actaea, formerly Cimicifuga) such as ‘Hillside Black Beauty’, ‘Brunette’, and ‘Black Negligee’.  ‘Firecracker’ hairy loosestrife (Lysimachia ciliata) is a clumping, non-spreading species, 3 to 4-feet high with dark reddish leaves, as is the ‘Chocolate’ cultivar of white snakeroot (Eupatorium).  The latter is best in warmer regions (USDA zone 5b, average minimum of -10 to -15 degrees F in winter).
Lower at under 2 feet high are some dark-leaved perennial geraniums, such as ‘Espresso’, ‘Midnight Reiter’, and ‘Elizabeth Ann’.  Similar in height but more upright and less mounded is ‘Bressingham Purple’ Jacob’s ladder (Polemonium).  Many such purple-leaved perennials will have less color, being more green, when grown in part shade rather than full sun.  One that does hold its reddish-purple leaf color well through fall is the upright relatively new sedum ‘Postman’s Pride’.  ‘Lady in Red’ painted fern (Athyrium) has bright red stems in mid-fall. ‘Bonfire’ cushion spurge (Euphorbia) has bright red fall leaf color, but needs a warmer climate (USDA zone 5b) or reliable snow cover to survive.
For even lower red to purple-leaved perennials, about a foot high, are the many dark-leaved coralbells (Heuchera). These include some of the top-rated in our Vermont trials (see the above  research website) including ‘Blackout’, ‘Dark Secret’, and ‘Frosted Violet’.
While not perennial, the kale and cabbages are worth mentioning as they provide some of the best blue to dark red and purple leaves into late fall—often until Thanksgiving or after.  Some are lower, a foot high, while others such as scarlet kale and crane bicolor kale reach two feet—the former with dark red fringed leaves, the latter columnar with pink to white coloring at the top.
There is a flower to mention too in this reddish color spectrum. ‘Sheffield Pink’ is a hardy chrysanthemum cultivar, blooming salmon pink in mid to late fall and one of the last plants to bloom.  While it often survives in colder areas, the season may be too short for it to actually bloom.
For golden to yellow leaves, perennials are mainly the lower ones under a foot high.  For taller gold leaves, you may need to use shrubs such as golden-leaved evergreens or conifers. You can get nice golden color from bluestars (Amsonia), growing two feet or more high and resembling a shrub.  Or try Osmunda ferns for their upright golden long leaves, contrasting nicely with their brown “seed” stalks.
Some of the lower golden to yellow perennials for fall include ‘Angelina’ sedum, the golden creeping Jenny (Lysimachia), golden oregano, ‘Aztec Gold’ speedwell (Veronica), ‘Dickson’s Gold’ bellflower (Campanula), ‘Gold Bullion’ bluet (Centaurea), and ‘Illumination’ perennial periwinkle (Vinca).  Golden hakone grass (Hakonechloa) is good in sun or part shade in warmer sites (USDA zone 5b). Some golden perennials, such as the bluet, the golden ‘Sweet Kate’ spiderwort (Tradescantia), or those with gold variegation, often revert to green leaves.  To keep them golden or variegated you’ll need to cut off, or out, any such green shoots.
Then there are those with white or silvery leaves, often during the season and lasting through fall until they die back or are covered with snow.  Most are low, under a foot high, such as the lungworts (Pulmonaria) with their silvery to silver-spotted leaves, or the popular compact ‘Silver Mound’ mugwort (Artemisia).  There are a couple of taller silver mugworts too, such as ‘Silver King’, that can spread aggressively by their roots. There are a couple silvery cultivars of Siberian bugloss (Brunnera) such as ‘Jack Frost’ and ‘Looking Glass’.  The white dead nettles (Lamium) are a spreading groundcover, some with quite white or silvery leaves.
Marginally hardy in cold areas, better in USDA zone 5, are the toad lilies. These Asian imports have very attractive white flowers, often speckled lilac, in mid fall just over a foot tall.  For taller white flowers in fall are some asters, such as the heath aster (Symphotrichum ericoides), and the false chamomile ‘Snowbank’ (Boltonia asteroides), reaching 3 feet or more high.  
One of the best for a shimmering silver effect through fall, from its 6 to 8 foot high flower plumes, is the silver banner grass (Miscanthus sacchariflorus).  Be careful with this one and place in a bed by itself, as it is quite root invasive and will overpower most any other plant.  I keep threatening to try and remove mine, but each fall the plumes redeem themselves for yet another season, particularly with backlighting from the low afternoon sun. 
Keep the fall effect of your perennials in mind, both with fall pruning and with choosing plants for an extended season of color.

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