winter – The Garden Professors™

Mitchella repens … Partridge Berry … an Evergreen Native Groundcover for Shade

Partridge Berry in its Natural Setting

One of the questions that came up regularly when I was working the hotline at the local county Extension office, is a recommendation for an evergreen ground cover for shady spots. I had the same issue when I created my own shade garden … something that would have year round interest, but complement my desire to emphasize native species, although that was only one consideration.

The solution was literally right next to me, as a walk in my woods revealed with the lovely plant Partridge Berry, or Mitchella repens.

Not only is Partridge Berry (Mitchella repens ) beautiful, evergreen, shade-loving, and native to Eastern North America, but there’s also a fascinating aspect about its flowers and fruit, from a botanical, and evolutionary point of view.

According to the U.S. Forest Service Celebrating Wildflowers website, the “… genus name Mitchella was given to this plant by Linnaeus for his friend John Mitchell, a physician who developed a method of treating yellow fever. The species name repens refers to its trailing or creeping habit.”

Here’s the part I found fascinating: The plant is dimorphous, meaning “occurring in two forms”:

In late spring, two beautiful white flowers (with one calyx) each open their four petals to entice insects to collect their nectar. Each blossom has one pistil and four stamens. The pistil in one is short and the stamens are long. In the other it is just the opposite. … Because of this no flower can fertilize itself–all flowers must be cross-pollinated by insects, and both flowers must be pollinated to get a single healthy berry. A berry will stay on the vine until after the blooms appear in the spring unless a hungry bird finds it nestled among the fallen winter leaves.

How cool is that? The twin flowers produce, together, only one berry.

Here’s a closeup, where you can see residual evidence of the fusion. The berry is edible, and persists through the winter, assuming it is not consumed by “ruffed grouse, northern bobwhite, sharp-tailed grouse, and prairie chicken.

The fruit is also “frequently eaten by raccoons and red fox” and it has been reported that “partridgeberry made up 2.9 to 3.4 percent (dry weight) of the summer and fall diets of white-tailed deer.”

Here’s a picture of the two flowers in bloom.

It’s easiest to spot the plant in its natural setting while hiking in late Fall, or early Winter before snowfall, or early Spring after snowmelt.

Back to the Forest Service article:

Some gardeners consider Partridge Berry a must for winter gardens. During the cold days of late winter Partridge Berry is a treat to the eyes with its deep, dark-green leaves and occasional scarlet berries. In a garden setting this evergreen prefers shade, accepting the morning sun. Partridge Berry is extremely difficult to propagate from seed.

The best way to introduce this native into your garden is through 1 year old cuttings or by division. In the garden situation they will form a thick, substantial ground cover. Once established they are relatively trouble free with the only required maintenance of keeping garden debris from covering the mats.

As always, do not wild collect plants from public lands and only from private lands when the landowner grants permission. Partridge Berry is a commonly available plant from native plant nurseries especially those who specialize in woodland plants.

I love the symmetrical variegation in the evergreen leaves, a bright, light yellow line bisecting each leaf, and the delicate, less visible veins.

It’s a great alternative to Vinca, an introduced species from Europe that appears on invasive species lists in our area.

A Google search will reveal many potential on-line sources for buying Partridge Berry plants, or check with a local nursery, or independent gardening center in the native plant section.

A tale of two winters

I’m not sure we’ve ever been quite so ready for the calendar to turn to March. That’s assuming, of course, you live somewhere east of the Rockies. For people on the west coast, the sentiment is probably, “When are those people back East ever going to quit b-tching about their weather…” While I was dealing with 10” of snow and 25 mph winds whipping up 3’ deep drifts on Super Bowl Sunday, my friends back home in Washington state were mowing their grass. At this point I don’t even remember what my lawn looks like.

I have to confess that I thought winter 2014 was an anomaly and that we wouldn’t see weather that cold again any time soon, if ever. Boy, did I get wrong number. While winter 2015 is not exactly a carbon copy of 2014, I’m not sure most of us can tell the difference. In case dealing with sub-zero wind-chills for weeks on end wasn’t torture enough, I dug into the weather records from our automated Michigan EnviroWeather network to see how the past couple of months stacked up. To keep things simple I queried the records for the past twenty Januaries and Februaries. I just include those months since we don’t have any data for this March yet and those are the months we typically get our coldest weather, though we occasionally also get sub-zero in late December.

Over the last 20 years the past two winters have been by far the coldest, and it’s not even close. Over the previous 18 years the average daily low temperature for January and February was 17.0 deg. F. In 2014 the average low was 5.9 deg. F; this year it was 5.8 deg. F.

Daily low temperatures in Jan. and Feb. of 2014 and 2015 were more than 11 degrees below the average of the previous 18 years.

Not only was it colder on average but we’ve had more extreme cold events in the past two years as well. Between 1996 and 2013 we averaged less than one day per year with low temperatures below -10 deg. We were below -10 deg. F on eight days this winter and nine days last winter. The bottom end of our USDA Hardiness Zone 5 is -15 deg. F. We have been below that mark five times this winter, compared to twice last year and zero times in the previous 18 years.

Over the past 20 years we rarely dipped below -10 F. We've been colder than -10 seventeen times in the past two winters. — Over the past 20 years we rarely dipped below -10 F. We’ve been colder than -10 seventeen times in the past two winters.

Obviously this data is specific to mid-Michigan, but I suspect most locations in the Midwest and Northeast will have similar stories to tell. So what does all this mean? For one, our hardiness zones are what they are for a reason. Folks that like to ‘push their zones’ (you know who you are), have gotten away with it with impunity for nearly 20 years. This winter and last were time to pay the piper.

The owner of this Cedrus deodora 'Polar winter' (zone 6) had gotten away with pushing their zone for 10 years before things came to grinding halt in 2014. — The owner of this Cedrus deodora ‘Polar winter’ (zone 6) had gotten away with pushing their zone for 10 years before things came to grinding halt in 2014.

The other take home lesson is that climate doesn’t consistently move in one direction. Even if we’re in a period of general warming, extreme events will still occur. This is important to remember as we think about planning for projected future climates. We have seen the appearance of several climate-change friendly plants lists. In some cases the authors have simply looked at projected climate zones and moved plant selections northward. The problem with this approach is tree survival is based on extremes, not on averages.

You CAN grow it, but is it worth it?

As winter sets in here in Michigan, I’m seeing gardeners deploying winter protection. Like this, which I saw on a visit to Hidden Lake Gardens with some friends recently:

Well. Isn’t that attractive? Come around to the far side, and you see this:

Pinus contorta ‘Chief Joseph’ which is a stunningly beautiful conifer, green in the summer, this brilliant shade of gold in the winter. Sadly, those gold needles are also incredibly prone to turning a less brilliant shade of brown if exposed to too much winter sun and wind. Hence the ever-so-attractive sun-and-wind shade they’ve installed here.

Call me old-fashioned, but the point of a garden is to be pretty, and though you CAN wrap delicate shrubs in burlap or upend styrofoam cones over tender roses or even (yes, I’ve seen it) put little roofs over your hardy succulents to keep excess rain off of them, but is it really worth it? For me, if I have to put something ugly on my plants to keep them healthy, it isn’t worth it. In my garden, I’d lean towards something else I also saw on that visit:

Chamaecyparis obtusa ‘Crippsii’ No, it isn’t quite as stunning as the pine… but it will grow and not turn brown, with no fuss.

What about you? Are there plants you are willing to make your garden ugly to keep happy?

Don’t need a weatherman to know which way the wind blows

Posted by Bert Cregg
Yesterday afternoon I did a little fall garage clean-up and listened to former MSU Extension colleague Dean Krauskopf’s call-in gardening show on the radio. A couple callers in a man phoned the show worried about his Japanese maple tree, which had a near-death experience from this past winter’s severe cold. The man had heard this coming winter was supposed to be just as bad as last winter and he wanted to know how best to protect his struggling tree from further calamity. Dean quizzed the caller for details about the tree and the site and gave some reasonable advice to try to modify the micro-environment around the tree to limit exposure to winter wind and cold. But I wondered where the caller got his information that winter 2015 was going to be as bad as 2014. As if anyone around here needs a reminder; January-March 2014in Michigan was the coldest since 1978 and the 4th coldest on record, with most locations reporting snowfall totals well above average. Many surrounding states has similar winter weather issues.

To get some insights on predictions for the upcoming winter, I consulted with the two most trusted sources of such information: The NOAA Climate Prediction Center and the Old Farmer’s Almanac.

The Climate Prediction Center maps present probabilities of colder or warmer than average weather for a given three month period. The most recent NOAA projections available on-line are predicting near-normal temperatures for January-March 2015 for most of the eastern half of the country, above average temps for the Northwest and below average for Texas and Florida. NOAA predicts below average precipitation for the lower Great Lakes and Northwest and above average precip for much of the South.

Current NOAA temperature predictions for Jan-March 2015

Current NOAA precipitation prediction for Jan-March 2015

Apparently, however, Dean’s caller is dismissing NOAA and all of their satellites and computer models and is relying on the Old Farmer’s Almanac instead for his long-term weather outlook. The Old Farmer’s Almanac is currently predicting colder and drier than normal for most of this upcoming winter for the lower Great Lakes.

Current temperature outlook for lower Great Lakes regions from Old Farmer's Almanac. — Current temperature outlook for lower Great Lakes regions from Old Farmer’s Almanac.

So, how much stock should we place in these predictions? Let’s step inside the Wayback Machine for a moment and see what each source was saying a year ago about the then-upcoming winter of 2014. NOAA and the computers are up first.

For most of the eastern U.S., NOAA predicted a warmer than average Jan-March 2014 with normal precip. Ooh, sorry about that NOAA but we thank you for playing ‘Guess that Winter’! Please be sure to pick up your parting gifts on your way to our Loser’s Lounge.

September 2013 map of NOAA prediction for Jan-March 2014 temperatures.

September 2013 map of NOAA predictions of Jan-March 2014 precipitation.

Next up is the Old Farmer’s Almanac, which predicts winter weather based on… well, no one’s quite sure. In any event, this time last year the Almanac predicted Jan-March 2014 would be mostly warmer and drier than normal for the lower Great Lakes. Oh no, bummer Almanac. Looks like you and NOAA can commiserate in our Loser’s Lounge. And that means Old Man Winter repeats once again as our champion!

Old Farmers Almanac September 2013 weather prediction for Nov. 2013-Oct. 2014.

So, what does all this mean for Winter 2015? Even with huge datasets and sophisticated models, long term weather projections are an iffy proposition. And, as much as everyone loves to say, “See, the Old Farmer’s Almanac was the only one to get it right”, there is little evidence that it does better than chance alone. Beyond that all we can say with certainty is that NOAA and the Computers would make a really cool name for a rock band.

You and me Baby ain’t nuthin’ but mammals…

As spring slowly makes it appearance in the Midwest, homeowners and landscapers are likely to continue discovering damage from our record-breaking winter. While brutally cold temperatures and heavy snow loads took their toll in many areas, some of the most severe damage that occurred to landscape trees and shrubs this winter was caused by mammals.

Our long, harsh winter resulted in heavy feeding damage by deer, rabbits and voles, also called field mice. Depending on the age and type of plant and which animal was feeding on it, mammal damage can range from light pruning to death of a tree or shrub. Developing a strategy to deal with animal damage requires proper identification of the offender. Here are clues to identifying mammal damage.

Vole damage
Voles or field mice are small rodents that gnaw on tree and shrub stems. Voles do not hibernate and are active throughout the winter under snow, so feeding damage that occurred near ground-line when the ground was covered with snow is likely vole damage. Although they are small, voles can wreak a lot of havoc. They can easily kill small trees or branches on larger trees by girdling stems, or removing the bark around the entire circumference.

Voles (or field mice) can completely girdle trees.

Deer damage
During the winter, deer feed on the ends of many types of trees and shrubs. Evergreens, especially arborvitae, are among their favorites. In most landscapes in this area, a “browse line” is a common feature on arborvitae. Eastern white pine, maples, birch, dogwoods and viburnums are also favored trees deer browse. This winter, I received reports of deer browsing on secondary species, such as Austrian pine, reflecting the severity of the winter.

Rabbit damage
Rabbits can cause damage that may resemble feeding by either voles or deer. Like deer, rabbits will chew the ends off of deciduous trees and shrubs. A close inspection of the end point will often indicate the culprit: rabbits typically leave a clean, angled bite mark, whereas deer tear or break stems, leaving a rough edge. Like voles, rabbits can also girdle stems of trees and shrubs. In winters with heavy snow cover like this one, the height of the damage can provide a clue; vole damage will extend down to the soil surface, while rabbits work above the snow-line.

Clean, angled bite-marks: A telltale sigh of rabbit activity.

Managing mammal damage
Managing mammal damage is often difficult and multiple strategies may be needed. Excluding deer with fencing can be highly effective, but is not practical in many instances. Deer repellents can also be effective, but may wear off over time or become less effective as deer become hungrier as winter wears on. Around our place, our dogs to a good job of keeping deer and rabbits at bay, but of course require their own care and feeding.
Reducing weeds and ground cover can help to reduce damage by rodents by eliminating cover from their predators. Trapping may be effective for controlling rabbits, but is usually not practical for voles. Baiting can be used for voles, though care must be taken to avoid poisoning non-target animals. In some situations, erecting raptor perches can also be helpful in keeping rodent populations down.

Feel the burn…

One of the most obvious impacts of this winter’s winter is rapidly becoming apparent in Michigan and other parts of the Midwest: winter burn on conifers. The primary symptom of winter burn is needle browning, especially on evergreen conifers in exposed locations. Needles may be damaged by extreme cold or the browning may be associated with winter desiccation as needles lose moisture during brief warm-ups. Winter burn is one of those situations that draws a lot of attention because it can look devastating; yet it often has relatively little long-term impact on plants.

Winter burn on dwarf Alberta spruce in Michigan

The key to the lasting effects of winter damage on evergreens is the extent to which buds are damaged.
With a little practice it is relatively easy to determine the state of conifers buds. With your thumb and forefinger pull the bud scales from the top of the bud. With a good hand lens or dissecting scope you will be able to see the bud primordia. On healthy buds this will be bright green; on damaged buds the primordia with be brown or black.

Buds from conifers with severe needle browning may be alive (top) or dead (bottom).

I recently examined buds from Douglas-fir trees on campus that had severe needle browning this winter. In several cases, trees had severe needle browning but the buds were fine. These trees will likely put on a normal growth flush this spring and in a year or two it may be difficult to tell they were ever damaged – assuming we don’t have a repeat of this winter’s severe weather.

A 'snow-line' indicates the depth of snow when needle injury occured — A ‘snow-line’ indicates the depth of snow when needle injury occured

On some other trees, however, the buds had been killed by this winter extreme cold. This doesn’t mean these trees are dead – they may still form adventitious buds along the stems – but it will certainly set them back and will likely impact their form and symmetry.

How cold WAS it?

The line ‘How cold WAS it?’ has been a lead-in for stand-up comics for years; as in, “It was so cold politicians had their hands in their own pockets…” or “It was so cold the mice were playing ice hockey in the toilet bowl…” Like everyone, I’ve heard lots of discussion these days about just how cold this winter has been. We certainly know that this winter bucks a recent trend of relatively warm winters in the Midwest over the past two decades.

However a popular notion around these parts, especially among old-timers, is that “this is the way winters used to be…” I’m a relative newcomer to Michigan, currently experiencing my 15th winter here. This is, by far, the coldest winter since I’ve lived here. But could this simply reflect my lack of perspective as a newbie? To gain a little insight, I pulled the long-term weather data for Lansing, which dates back to the 1880’s. I compared the daily minimum temperatures from this winter with the long-term average low temperatures and daily record lows.

The results will come as no surprise to anyone who lives east of the Rockies. It’s been cold. How cold WAS it? Certainly well below average, especially since the Holidays. As of yesterday, 41 of the last 52 daily lows have been below average and we have been below 0 deg. F 19 times. Despite the prolonged cold, we have not broken any daily records although locations near here have.

So, are the old timers right? Are we just getting a glimpse of the way things used to be back in the day? The data suggest they are probably experiencing a bit of selective memory. If you’ve lived here long enough you’ve seen a few winters this cold and even colder. But this January will go down as one of the 10 coldest (at least) on record, so the idea that winter’s weather is like the ‘old normal’ is a bit of a stretch.

The Ice-pocalypse of 2013: Winners and losers

Power has been restored to most of the nearly 600,000 people in Michigan that lost electricity during the ice storm that hit last weekend. The storm coated trees with an ice coating an inch thick in many locations, resulting in widespread tree damage. Exceptional events such as this remarkable ice storm provide numerous opportunities to make some observations about trees and how there were impacted by the event. Here are some notes based on observing trees near my home in DeWitt, MI and driving around Lansing, East Lansing, and the MSU campus. Please note these are general trends and impressions. For nearly every item listed I’m sure someone will be happy to point out exceptions.

Conifers vs. Deciduous trees. Without a doubt the ice-storm was much harder on deciduous trees than conifers. Elms, maples, oaks, locusts, and birches were all hard hit by the storm. Conifers, for the most part, came through pretty well. The main exceptions were pines, particularly eastern white pine and Scots pine, which received widespread damage. Firs and spruces generally fared well. A big surprise (at least to me) was that there was comparatively little damage to arborvitae, which often end up splayed after heavy snow. In the current storm the ice tended to meld into a solid coating, essentially fusing branches together and reducing splayage.

Spruces were largely unaffected by the ice load

Old vs. Young. Young trees came out relatively unscathed compared to mature trees. In many cases young trees were bent over by the ice but were recovered after the thaw.
The most common damage that occurred on large trees was high crown breakage. One fortunate aspect of the storm is that there was relatively little wind while the trees were coated with ice. As a result, most of the force on braches was downward and the vast majority of the breakage was on smaller limbs (3-4” diameter). Of course there were exceptions to this, but we did not see widespread uprooting of trees or effects of shear forces that usually accompany wind-storms.

Native vs. Exotic. As one would predict, this one was pretty much a push. Silver maples, which are native to this region were among the most heavily damaged trees. Likewise native eastern white pines and oaks were also widely damaged. Among exotics, Siberian elm and Japanese pagoda tree had extensive breakage.

Almost all Japanese pagoda trees on campus has extensive branch damage

Baldcypress, an exotic in Michigan, had little ice damage

Managed vs. Unmanaged The ice-storm did reveal some cases where regular tree maintenance can pay off. The MSU campus has dozens of English oaks that have been planted over the years. At one point these were thought to be the ‘wonder tree’ that would be perfect for street and landscape planting in the Midwest. And they do have many great attributes; nice form and leaf color, moderate growth rate, tolerance of poor site conditions. Unfortunately they suffer chronic branch mortality due to two-lined chestnut borer. Just a few weeks ago our campus grounds crew came through and did some maintenance pruning on these oaks, removing lots of dead wood from each tree. Since the tree crowns had already been cleaned up, there was almost no breakage in these trees during the storm. One might argue that the net result was the same, whether the arborists took the limbs down or the storm did, but when dealing with trees it’s always preferable to take things out on your terms and timetable rather than the weather’s.

These English oaks lost very few branches during the storm thanks to recent maintenance pruning

(Not so) pretty in Pink

The weekend’s weather forecast portended some lousy conditions and, unfortunately, this time the forecasters got it right. The outlook map for the Lansing area put us squarely in the dreaded Pepto-Bismol pink ‘Icy mix’ swath from Oklahoma to Maine.

Last night and this morning was a non-stop cacophony of “Snap! Crash!” as icy limbs headed earthward. About 4:30 this morning my wife saw a bright flash burst across the street and almost immediately we heard all our of appliances stop. No power. After breakfast I negotiated a slalom course of downed tree limbs to a nearby supermarket which was operating on its emergency generator. Last minute Christmas shopping had instantly given way to stocking up on bottled water, camp-stove fuel, batteries, and Presto logs.

The short drive back and forth to a store made the immensity of the storm immediately apparent. Most people we know are without power and I suspect for most of us it will be several days if not longer before we get it back. Hats off to the men and women that are heading out to get things working again while the rest of us are staying inside and trying to keep warm.

I did get out and get a few photos around our place this morning to share, in case you’re in a location where you’re not experiencing the 2013 Ice Storm up close and personal. My alternative title for the post was “Beauty and the Beast.”

Our silver maple did what silver maples do in storm

Ice coating was over 1' thick in some cases — Ice coating was over 1′ thick in some cases

Lot of tree breakage everywhere. I'm surprised anyone has power today — Lot of tree breakage everywhere. I’m surprised anyone has power today

Long winter proves that climate change is a hoax

Just looked at the forecast for the week – Thursday’s forecast high temperature is 32 deg. F. This is a far cry from last year’s record-shattering 86 on the same date. Clearly all this blabbering about climate change is just a bunch of hysterical nonsense.

As sportscaster Lee Corso would say, “Not so fast, my friend…” While winter 2013 can’t compete with winter 2012 in terms of record-breaking warmth, this winter has continued a trend which may have profound implications for landscape and garden plant selections.

As you’ll recall, last winter saw the release of a new USDA Hardiness zone map which indicated that most areas of the US had warmed by at least one-half hardiness zone (5 deg. F) since the previous map was produced 22 years earlier. Hardiness zones are based on average minimum temperatures; in other words, what’s the coldest temperature you’re likely to see in a given winter. As it turns out, minimum temperatures have been warming faster than overall average temperatures. So much so, in fact, that one researcher declared the brand new hardiness map dead on arrival. Nir Krakauer at City College in New York noted that if we look at trends, rather than averages, many areas of the US are already another half a zone warmer than the new USDA map.

Minimum winter temperatures are warming at a much faster rate that average temperatures

Last week I gave a presentation at the Minnesota Shade Tree Shortcourse and pulled together some cold hardiness data for the Twin cities. According to the new USDA map, Minneapolis-St. Paul is now zone 4b (-25 to -20 deg. F). One way to think of this over a long enough time-span, about 1/3rd of their winters should reach a low in that range, 1/3rd should be slightly warmer, and 1/3^rd should be slightly colder.

The new USDA map indicates the Twin cities are in zone 4b

I pulled out the winter weather records for Minneapolis-St. Paul since 2000, including winter 2013. In the past 14 winters temperatures in the Twin cities have dipped to their hardiness zone level exactly once, 2004. All other minimum temps were at least 5 deg. F warmer.

Annual minimum temperatures at Minneapolis-St. Paul airport (MSP) have reached zone 4b levels only once since 2000.

Obviously a 14 year record is not sufficient to build a hardiness map. Nevertheless, if someone tries to use this winter as proof that climate change is hoax; just remember, minimum winter temperatures – the temperatures that serve as a primary limit of which plants can grow where – tell a different story.