|Yard & Garden Line News
Volume 5 Number 18 December 1, 2003
Mums and More--Flower Breeding Update, Part 1
Beth Jarvis, Yard & Garden Line
Neil Anderson always hopes for at least one winter night of -50° F. No, he's not a masochist; he's a plant breeder. Mild winters are "non test winters" according to Neil, who works extensively in creating new, winter hardy perennials. When you're breeding for hardiness, you'd like to be sure they'll make it through a normal winter.
He's carrying on the chrysanthemum breeding work started in the 1920s in the Department of Horticultural Science at the University of Minnesota. The program has not always focused on plant hardiness; the U has released "florist" mums, as well, that are annuals.
Now, Neil and his grad students are looking at a number of perennial plants and even an annual or two!
What's new in the mum fields?
Neil and his research assistant, Esther Gesick, have discovered a rapid selection method that enables the breeders to screen for winter hardiness.
Growing points are
They found a strong correlation (>80%) between the number of visible chrysanthemum growing points persisting after a hard frost and a plant's winter hardiness.
The more growing points visible, the hardier the plant. (This may be due to the increased amount of food reserves found in the subterranean rhizomes.) The best thing is, they can make evaluations by simply walking the test field--they don't have to dig the plants up to count the rhizomes! This discovery will speed new selections to market by possibly as much as 10 years.
It takes a lot of work to determine cold tolerances. To prove the rapid selection method works, this is what they did:
They raised known hardy mums and known marginal mums in field trials. They dug representative samples of each clone in mid-October of the two test years. They washed the soil from the roots and weighed the plants. They counted emerged growing points and those that had not yet emerged. They measured the five longest rhizomes. Then, they dried the plants, in paper bags in an oven at 88°C (194°F) for 168 hours. Then, they recorded the dry weight. (Fresh vs. dry weights are numbers dearly loved by plant people as a means of evaluating size of plants.)
To confirm the hardiness, they conducted freezer trials on both excised rhizomes that were put in tubes filled with vermiculite and frozen as well as on field dug crowns. The one year old clumps were dug and planted in field soil into large containers then acclimated to 2°C (35.6°F). Entire containers were then subjected to the freezer.
Non-hardy mum (top)
Hardy mum (bottom)
Freezer timers adjust temperatures to those specified for the desired duration.The mums were frozen to 0°C (32F), -6°C, (21.2°F) -10°C (14°F) and -12°C (10.4°F).
While 10.4°F sounds warm, remember that soil temperatures are relatively warmer in winter than air temperatures would indicate. Plant breeders talk of LT50s, for Lethal Temperature at which 50% of the plants in a study die. The LT50 for a lot of plants is -12°C.
Soil moisture also plays a role in winter survival so mulching is recommended to preserve soil moisture as well as minimize frost heaves in winters with little snow. Plants that have been in the ground long enough to becomes established and start acclimating for winter also have an edge.
But what about new mums??
So what's new in the mum world? Prostrate mums--horizontal growers that have one main stem but don't root adventitiously, along the stem are the next new thing. They're calling them "wave" (as in petunia). Neil says they have "all the colors".
The prostrate mum research was funded by the Richard Widmer Research and Education Fund. The money is a voluntary ˝ % "tax" on greenhouses collected by wholesalers to fund research. (Dr. Widmer was an early leader of the mum project.)
There are 5 of the "My Favorite" mums out and "many more in the pipeline". To read more about the five new "My Favorite" mums click here:
To learn more about the mum breeding project: click on:
Next Month: Truly hardy Gaura. Lillies from seed that bloom all season. Dwarf, fragrant gladiolus.
"Chestnuts roasting on an open fire…"
Janna Beckerman, Extension Plant Pathologist
Most people know at least the opening lyrics of "The Christmas Song." However, not everyone knows why most of us don't actually roast chestnuts (even in the oven), or, that if you actually do roast them, that you are roasting the inferior-tasting Chinese chestnut. So, to paraphrase another song, "Where have all the Chestnuts gone?"
The chestnut blight fungus, introduced at the end of the 19th century, has virtually eliminated the American chestnut as a commercial species from the eastern hardwood forests. The American chestnut had an important role in American life. This huge, majestic tree, with a very straight stem was dubbed "the redwood of the East." The wood, similar in many ways to oak but with incredible rot resistance, was said to follow a person from cradle to grave. Log cabins built in the late 1700's are still standing today-testimony to the rot resistance of the wood. The nuts were used to feed everything from hogs to humans. The American chestnut was Americana.
The disease, caused by the fungus Cryphonectria parasitica, was introduced into New York and spread quickly. As an introduced pathogen, resistance to this disease in the American chestnut population never evolved. This disease resulted in the virtual destruction of the American chestnut in the hardwood ecosystems from Maine to Mississippi. What was once the premier tree in the forest canopy was reduced to insignificance. A study in Pennsylvania in 1911 estimated the state loss at over $250 million dollars. In the succeeding 40 years, 4 billion trees were estimated to be killed.
Will the blight end the chestnut?
The farmers rather guess not,
It keeps smoldering at the roots
And sending up new shoots
Till another parasite
Shall come to end the blight.
- Robert Frost
A prolific sprouter, roots from trees cut or killed many years ago continue to produce sprouts that survive to the sapling stage before being killed. A few sprouts have managed to achieve heights of 40' before succumbing to the blight.
In the 1950's, an Italian scientist noticed a reduction in canker growth in infected European chestnuts. This was the first report of hypovirulence (reduced virulence) in the natural population of the fungus. Hypovirulence is the reduction of fungal virulence due to infection by mycoviruses (viruses that infect fungi). Was this the parasite that Robert Frost had hoped for?
In 1976, the first case of natural hypovirulence in North America was reported in Michigan. Other states where the chestnut once reigned found these isolates as well. For the most part, these hypovirulent fungi lack the orange pigment found in virulent strains and have fewer pycnidia, making it readily recognizable in the field. Because the pathogen is infected by a virus, it grows more slowly. This reduction in growth provides a sufficient window to permit the tree to compartmentalize it by producing callus tissue.
As promising as this sounds, there are two major problems in using hypovirulence to manage the disease. First, hypovirulent strains suffer a reduction in sporulation, making them less fit than their virulent counterpart. This reduces the likelihood of their spread, and contact with virulent strains in nature. Most successes using hypovirulent isolates to control disease have required human help.
Despite the fact that there are many people who would volunteer to spread hypovirulent isolates, there is a second issue as well. In order to transmit the virus from a hypovirulent isolate to a virulent isolate requires hyphal fusion. Many fungi, including Cryphonectria, have natural barriers to prevent hyphal fusion between strains of the fungus. When hyphae can fuse and exchange material, they are said to be vegetatively compatible, and in the same vegetative compatibility group. In North America, unfortunately, we have many vegetative compatibility groups, making the spread of hypovirulence difficult.
Plant pathologists love disease, but it has to be a fair fight between co-evolving organisms. There is nothing "fair" about Chestnut blight. Although the Chestnut persists, the loss of such a dominant component to the ecosystem is a tragedy. To date, work continues to develop blight resistant chestnuts. In time, the American chestnut may become more than a distant memory, and 'The Christmas Song' may be more merry than poignant.
Indoor Plants Bring Cheer in Darkest Winter
Deborah Brown, Extension Horticulturist
As Minnesotans, we're only too aware that December, with its short days and long nights, lives up to its reputation as the darkest month of the year. Even when weather is clear and sunny, many of us get up in the dark and come home in the dark. To make our homes more welcoming, we rely on lively indoor plants, especially as the holiday season approaches. Contributing both color and beauty, they're also a tangible reminder of the natural world at a time when most outdoor greenery is covered with snow.
Flowering plants and tropical foliage plants make wonderful holiday gifts, too, provided a few precautions are taken to deal with cold temperatures. You needn't worry about plants that are delivered by florists or garden centers. Those firms use heated vans or trucks, and wrap plants thoroughly for the short trip from their vehicle to the recipient's home. If you are delivering a plant yourself, though, be sure to warm your car or van first. Then make certain the plant is wrapped or even double-wrapped, with a large plastic bag trapping air around it to provide insulation.
When choosing flowering plants, keep in mind that some will hold their blooms much longer than others. Poinsettias and orchids, for example, can be expected to look good for months, given the right care and location. Depending on bud count, cyclamen may bloom for months, also. Bromeliads don't produce what we think of as "typical flowers," but their flowering spikes have been known to last six months or more.
Other plants will get you through the holiday season, but not much longer. Chrysanthemums should last three weeks or so; azaleas, about the same – if you have a relatively cool place to display them. Christmas cactus only bloom for two to three weeks, but may be kept and made to re-bloom for years to come.
If at all possible, buy flowering plants with only some of their buds wide open and others still beginning to open. Then you – or the person you give them to – can enjoy watching the blooms expand. A plant with all its flowers fully open may be showier at first, but generally won't last as long. Of course, if you don't have a bright place for the plant, flowers from buds that open in your home may be smaller and less colorful than those that grew in the greenhouse.
Here's a rundown on choosing and caring for a few of the most popular holiday plants. Your favorite florist's shop or garden center will have many additional selections, and can often supply care sheets for them.
Greenhouse growers have poinsettia production down to a science, and it shows in the final product. Not only are there new and more beautiful varieties each year, they seem better adapted to growing under ordinary home conditions.
To keep a poinsettia looking good for a long time, begin with a robust plant; one with an abundance of large, well-colored bracts or "petals" surrounding the odd little gold flower at the tip of each stem. Once in your home, be sure the foliage receives some direct sunlight every day. Don't display your poinsettia in a dark location for more than a day or two at a time. Water it thoroughly whenever the soil surface begins to dry; leaves will curl and yellow if you allow the plant to wilt repeatedly. After about six weeks, begin a very light fertilizer regime. If you're up to the challenge you can put the plant outdoors after frost, then bring it indoors in early autumn and force it into bloom again.
It's amazing how many Christmas cactuses are passed down from one generation of gardeners to the next. Anyone who's seen a large Christmas cactus loaded with buds and jewel-like blossoms will find it hard to resist smaller versions so commonly available this time of year. Each holds the promise of turning into an "heirloom" plant of great beauty. And they're not difficult to grow.
Understanding that Christmas cactuses -- unlike most other cactuses -- are not desert natives, but hail from the humid environs of tropical and sub-tropical forests, gives us clues as to their care. When blooming, place them in bright filtered light rather than a sunny, south-facing window. Keep the soil relatively moist at all times, fertilizing it lightly every two to three weeks. Buds will hang on better and open flowers will last longer if warm daytime temperatures drop to 60 - 65 degrees at night. Once flowers fade, allow the soil to dry more between watering.
Put these plants in a porch or outdoors in the partial shade of a tree once frost danger has passed. It's easy to get blooms each year by exposing Christmas cactuses to cool night temperatures in autumn or making sure they receive artificially short days after you bring them back indoors.
Florist's cyclamen are available in an array of stunning colors ranging from pure white to pinks, reds, and fuchsias. Don't base your choice solely on the handful of blooms you see held high above the foliage, though. You need to be snoopy when you pick a cyclamen. Gently move a few leaves apart to look for lots of developing flower buds beneath them. The more buds you see, the more potential for prolonged bloom time. As older flowers fade they'll be replaced with new ones.
Two important environmental factors must be in place to keep cyclamen blooming well. They need good bright light during the day, followed by cool temperatures at night. Ideally, night temperatures should fall between 50 and 60 degrees, but even a drop to 62 or 65 will help. Water and fertilize as described for poinsettias. Getting cyclamen to bloom again is possible, but difficult. Most people just toss the plants once they begin to look shabby.
Few holiday plants rival azaleas for visual impact, with their masses of brilliantly colored blooms. Because they're propagated from cuttings, even tiny plants are covered with flowers. These plants are perfect for anyone who keeps their home on the cool side, growing best when daytime temperatures don't exceed 68 degrees.
Night temperatures are even more critical. The ideal is someplace in the low to mid 50's – or as close to that range as possible. (Set them on the floor in an entry hall, on stairs to the attic, or directly next to a patio door each night.) When temperatures are too high, particularly at night, their flowers just won't last as long.
Keep azaleas consistently moist while they're blooming. Be sure, though, to cut a hole in the decorative sleeve covering the growing pot, so excess moisture may be discarded. Since most people just toss these plants once their flowers fade, it's not critical to keep them in a bright location. If, however, you want to try to force another round of blooms from your azalea next fall, you must put it in a sunny window and fertilize with plant food made for acid-loving plants, before moving it outdoors into dappled shade for summer.
A Final Minnesota Gardening Calendar Reminder
Deborah Brown, Extension Horticulturist
If you're looking for the perfect last-minute gift for anyone who enjoys gardening, pick up one of our Minnesota Gardening calendars. They're available through local county extension offices, U of M bookstores, and by mail, directly from the U. This year's calendar features a page about growing hardy fruit trees, many of which were developed by U of M plant breeders specifically to withstand our harsh climate.
2004 Garden Calendar
The calendar, our fourteenth, contains frost and hardiness zone maps along with information about the many Minnesota institutions and organizations that serve the gardening public. Minnesota Gardening calendars are best known, however, for their monthly garden and landscape tips written specifically for people who live in challenging, cold climates such as ours.
If you want to save some of the hassle of shopping, you can make credit card purchases of the calendars on-line at http://www.extension.umn.edu/distribution/horticulture/DG7754.html or by calling Extension's distribution center, directly. Their phone number is 612-624-4900 in the Metro calling area, or toll-free, 1-800-876-8636, in greater Minnesota.
Jeff Hahn, Assistant Extension Entomologist
When people see small-sized flies in their home, their first thought is that they must be fruit flies. However, there are a handful of other kinds of small flies that may also be found in homes. One common type is the phorid (FOUR-id) fly also know as humpbacked fly, coffin fly, and scuttle fly.
This fly is about 1/8 inch long, tannish to dark brown and has a hump-shaped thorax. Under magnification, you can see the characteristic pattern of veins in their wings comprised of two strong veins at the top of the wings with three or four parallel veins radiating out from there.
Fruit flies and phorid look similar and can be easily confused. The easiest way to distinguish between them is the eyes. While fruit flies usually have red eyes, phorid flies lack this and have dark colored eyes. Phorid flies also move characteristically in a rapid, jerky motion. Although they can fly, they often prefer to walk or run on counters, walls and other surfaces. Fruit flies (as well as other small sized flies) more commonly fly.
Phorid flies are found in many types of moist decaying organic material. They can be found in drains, especially in bathroom sinks and showers, food residues in trash containers, rotting food, infrequently used garbage disposals, dirty mops and old dish rags, potting soil, organic material on the bottom of pet cages, and sewage from broken sewer lines. They are also common in schools and other buildings with a food service area in the cracks of kitchen equipment or underneath them. They have even been know to infest mausoleums and feed on human corpses!
These flies can occur in large numbers and become a significant nuisance. Phorid flies can potentially be a mechanical vector of disease organisms because they visit rotting foods and generally unclean areas. Although this can happen, they are generally not considered to be a medical problem.
The most effective control of phorid flies to locate and remove the moist organic material that the larvae develop in. However, finding the food source may be easier said than done and often requires detective work to locate the infestation. Remember that this could be found in a variety of different places. Be flexible in your thinking as the problem could occur in unexpected sites. The keys are moist, organic material.
Despite this work it takes to find the source, it is worth the extra effort and will result in a long-term solution to the problem. It may be tempting to spray the adult flies with an insecticide to control the problem. However, as long as there is a food source, the phorid flies will continue to occur.
Get the low down on this month's insect pests at
In October I visited Finland and took the boat to Tallin, Estonia for a day. This gate was in the old town section of the city.
Gate in Tallinn,
My fall garden-dug amaryllis are going dormant as bare bulbs. I was reminded of a call I took about overwintering amaryllis when I worked for the then Dial U Clinic. My client asked why the pots of overwintering anaryllis are placed on their sides. I'd never heard about that and ask Deb B about it. There's no physiological reason for doing it; it's just sometimes done as a reminder to not water them!
Next issue I'll wrap up the story of Neil, Esther and grad students and the perennials. In February, we'll hear from Pete Moe, Mn. Landscapae Arboretum. We'll learn all about a day in the life of the arb.
This winter, we'll visit the North Central Research and Outreach Center, formerly the NC Experiment Station, in Grand Rapids.
In a couple of months, Dave Ragsdale will expound on the changing face of insecticides. Scientists are finding new insecticides that are more narrowly focused to target specific pests. The general purpose, broad specturm, ecologically harmful insecticides may one day be a thing of the past.
In the future, you'll also get to meet Dr. Tim Kurtti, who does deer tick research.
And before long, it will be spring.
Please feel free to cut and paste any of the articles for use in your own newsletters. All we ask is that you give our authors credit.
Back issues Yard & Garden Line News are on the Yard & Garden Line home page at www.extension.umn.edu/yardandgarden/. Our home page has clickable links to most of the components of the Yard & Garden Line, such as Bell Museum of Natural History, INFO U and the Soil Testing Lab.
Deb Brown answers gardening questions on Minnesota Public Radio's (MPR) "Midmorning" program on the first Thursday of every month at 10 a.m. Katherine Lanpher hosts the program that is broadcast on KNOW 91.1 FM, and available state-wide on the MPR news radio stations.
The Yard & Garden Clinic will close December 12 due to budget cuts. Calls from the general public will no longer be accepted. Samples will not be accepted.
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