November 2022 – The Garden Professors™

Let it snow, let it snow, let it snow?

If you follow current weather news, you have likely read the astounding story of the recent lake effect snowfall in Buffalo, New York, and other areas downwind of the Great Lakes, where over 6 feet of snow fell in just a day or two in some locations. My mom, who still lives in Grand Rapids, Michigan where I grew up, reported that in her city some areas got up to 30 inches during the same time frame. So this month I want to discuss lake effect snows and how heavy snows can affect your trees and gardens.

What is lake effect snow?

Lake effect snow is snow that is caused or enhanced by differences in the temperature of warm water in the lakes and the cold Arctic air that blows over it. Calling it “lake effect” is a bit of a misnomer, since cold, dry air blowing over a warmer ocean can cause the same effect. In the United States, it most often occurs downwind of the Great Lakes, especially in fall when the lakes are still warm and the air blowing in from the north is much colder and drier than the lake surface. It can even sometimes occur downwind of smaller lakes or reservoirs if the conditions are just right.

Diagram

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As the cold dry air crosses the warm water, copious amounts of water vapor evaporate into the air mass and once that warmer, moister air blows onshore again clouds drop huge amounts of snow in the areas downwind of the lakes. The snow usually falls in heavy bands that drop snow in areas that are highly dependent on the direction of the wind. Often the bands are just a few miles wide but if you drive through one your visibility can drop to near zero in just a short distance. When I lived in Valparaiso, IN, near the south end of Lake Michigan, winds blew straight from the north for much of the month of December 2000 dropping 32.0 inches of snow when Decembers there usually get just a few inches, thanks to the lake effect snow that occurred. (I moved to Georgia the next month, although it was not because of the snow—mostly.) As winter progresses and the lakes get colder with more ice cover, lake effect snow is reduced because of the decrease in available water vapor so fall and early winter are the prime times of year for the heaviest lake effect snow.

In this case, weather forecasters were well aware of the potential for record-breaking snow because of their knowledge of the lake temperatures plus the computer-generated forecasts of wind direction and persistence over time. Winter storm warnings and maps of predicted snowfall were produced well ahead of time. Even so, the amount of snow that was produced from this historic event is still amazing.

Source: Carolyn Thompson / AP Photo

Why did Buffalo experience such extreme snowfall amounts?

Buffalo is known for its incredible snowfalls due to its position downwind of Lake Erie, a long and shallow lake that is usually warm well into fall. The long distance of the wind blowing over the lake (called the “fetch”) allows the air to pick up tremendous amounts of water that becomes snow as it hits the land NE of the lake; the exact location of heaviest snow depends on the direction of the wind over the lake (see my poorly drawn map annotated on a screen capture of the Earth Nullschool streamline map for the day of the heaviest snowfall below). In this month’s case, the lake had temperatures well above the long-term average, and the wind across the lake was very consistent over a few days, allowing the snow to pile up dramatically. In some locations snow was falling at the rate of several inches an hour and the extended period of snowfall allowed it to build up to over six feet in some locations in just a day or two, while other areas not along the direct path of the wind received much less. The area of heaviest snowfall shifted as the winds changed direction over time.

The result of this weather event was the nearly complete shutdown of Buffalo and other areas affected by the heavy snow. Even a city that experiences as much annual snow as Buffalo does can be stopped in its tracks for a while by the sheer volume of snow that has to be removed. The weight of the snow also caused problems for a number of building roofs and caused some power outages as well. Even the professional football game between the Buffalo Bills and the Detroit Lions had to be moved from Buffalo to Detroit because of the impossibility of clearing out the open-air stadium and the roads around it for fans to get there safely (or at all).

Does climate change affect lake effect snow?

A warming climate does have some impact on the conditions that make lake effect snowfalls most likely. The lakes are generally staying warmer later into the fall, so when cold continental air does develop over Canada and move across the lakes there is more potential for large amounts of water vapor to be evaporated, increasing the chance of heavy snow. It is likely that there may be some reduction in the production of the coldest, driest air in polar regions, but it will still occur often enough for lake effect snow to continue to be a climate factor downwind of the lakes. It is more difficult to say how or if the weather patterns that determine the direction of wind flow will change as the climate gets warmer.

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Source: Dan Taylor-Watt, Commons Wikimedia

How does heavy snow affect trees and gardens?

Lake effect snow is often very wet and heavy which makes damage to trees and power lines more likely. An average snowfall may have about one inch of water equivalent in ten inches of snow, but in a lake effect snow it is often more like six inches of snow to one inch of water equivalent which means it is very dense stuff to shovel. Wet snow may weigh up to four times as much as newly fallen regular snow per square foot. No wonder most heart attacks from clearing snow occur when this very wet and heavy snow has fallen.

The weight of this much snow can easily collapse the roofs of buildings. It can also do a lot of damage to tree limbs and shrubs, especially when the wet snow sticks and freezes to either needles or leaves adding to the weight on the limbs. Trees and bush varieties that are brittle or have poor branching structure are especially vulnerable to damage from heavy snow. Snow on the ground can help insulate the plants from very cold weather, but the moisture that is left after the snow melts can cause saturated soils that can negatively impact roots. Salt added to help melt the snow from paved surfaces can also harm plants and the deep snow cover in some lake effect storms can also provide cover for voles and other critters that like to nibble on bark.

For me, lake effect snow in my Michigan winter when I was growing up was the ultimate fluffy Christmas snow, with big fat flakes drifting down like a picture postcard. But when the flakes come down fast and heavy the holiday snow becomes a problem that can affect travelers, home owners, and gardeners too. I hope that as you travel over the holidays this winter, the snow that you see, whether you stay or go, is a delight and not an obstacle to spending time with your friends and family.

“This one secret hack will save you time and money!”

I’m resorting to clickbait tactics to get your attention. Here’s another – “Warning! Graphic photos follow!”

Uncorrected roots in containers or landscapes will create chronic water stress problems for trees.

If you have failing trees on your own property or on property you manage, you need to do one simple thing before you assume that pests or disease are responsible: you need to determine whether the root system is healthy and functional.

Now, I know you can’t see underground, but you can draw some informed conclusions based on whether you can see the root flare. To find the root flare, pull away any mulch or groundcover that’s obstructing your view. Once you can see soil, you should be able to see the root flare. If your tree looks like a utility pole (meaning you can’t see the flare), then it’s been planted incorrectly. This single mistake will have myriad consequences:

No flare = no chance

It’s buried too deeply – the f lare needs to be at the surface.
If it’s buried too deeply, it’s likely the tree was planted without removing the materials surrounding the roots. Bare–rooting woody plants before planting is crucial to their survival.
Roots that are buried too deeply will not have sufficient oxygen to establish a fine root system for water and nutrient uptake, much less develop any structural roots.
Moreover, without removing the materials around the root, the roots are less likely to establish into the surrounding native soil. Neither are you able to remove poor structural roots. Check out this post for more information.
A structurally flawed root system, stressed for oxygen and encased in layers of clay (or potting media) and various combinations of burlap, twine, and wire baskets, is not going to establish quickly or well. Increasingly, it’s not able to supply sufficient water to the growing crown.
Oxygen-stressed roots will die, compounding the reduced water uptake problem.
As the crown experiences chronic water stress, it will experience dieback while opportunistic pests and disease take advantage of a tree unable to chemically defend itself.
Opportunistic pests and diseases are not the cause of tree failure – they are simply indicators of an environmental problem. Proper diagnosis is discussed here and here.

Bare-rooting plants allows you to correct defective structural roots before planting.

You should be able to confirm lack of root establishment by performing the wiggle test (that’s the secret hack). This will allow you to see whether the soil around the roots moves. If it does, that means the roots are not established. If the tree has been in the ground for more than 6 months, it’s probably not going to establish. The sooner you can dig up and correctly replant a relatively newly planted tree the better your chances that will recover and establish.

The wiggle test!

Po-TAY-to, po-TAH-to: Let’s call the whole yam thing off!

As most folks in the US prepare for a Thanksgiving meal, or at least eat more Thanksgiving-inspired fall meals, potatoes and sweet potatoes often play a major supporting role in these most delicious victuals. Whether mashed, smashed, baked, candied, or turned into casseroles or pies, these starchy vegetables are stockpiled in grocery stores and markets in the fall for shoppers to turn into those tasty treats.

But sometimes there is confusion lurking in those grocery aisles and even in the minds of unwary shoppers….enter the “yam”. Wander down the canned vegetable aisle and you’ll see canned yams. Are they the same thing as sweet potatoes? And are they related to the standard potato that you usually mash, bake, or fry? I yam going to set the set the record straight.

First things first, sweet potatoes and yams are two totally different species so they are not the same thing. They’re even in different plant families so they aren’t even closely related. And neither of them are related to the regular old potato. So those “canned yams” at the grocery store are mis-named. They are sweet potatoes. Yams are rarely consumed or sold in the US, except usually though markets that sell specifically African/Caribbean foods.

Sweet potatoes are soft when cooked, thin/soft skinned, usually pretty sweet, and usually orange. Though there are some white-fleshed, less sweet varieties available. Native to tropical regions of the Americas sweet potatoes, or Ipomoea batatas, are members of the Convolvulaceae, or bindweed, family and are closely related to morning glories many of which are in the same genus Ipomoea. These sweet veggies are part of the root structure, so they are modified storage roots that store starches and sugars produced by the plant.

Yams, on the other hand, are white with a hard skin like tree bark, and are usually pretty dry when cooked. There are three main species of yams in the Dioscorea genus, which has its own family Discoreacea. Also tropical in nature, three different species were domesticated independently in Africa (D. rotundata), Asia (D. alata), and the Americas (D. trifida). Yams are monocots, meaning they are more closely related to lilies and onions than they are to sweet potatoes. Also, unlike sweet potatoes, the edible portion of a yam is a tuber, which is structure arising from modified stem tissue.

Piles of yams…that look nothing like sweet potatoes

And just to round out the tater trifecta – the humble potato. Sometimes called a white potato or an Irish potato (which are both bad descriptors for them because they come in many different colors, and while they are a staple in Ireland they originate from the Americas), these versatile spuds, Solaunum tuberosum, are members of the Solanaceae family and are closely related to tomatoes, Solanum lycopersicum. Their morphology has similarities to those of the yam, though, as they are tubers arising from the stem vs being a root like sweet potatoes.

So where does all the confusion come from?

There are various theories on how yams and sweet potatoes got caught up in this mash-up, and I don’t pretend to be an expert here. But the most common theory that I’ve seen is that enslaved African people held in the US south called the local sweet potatoes by the names they used for yams, as the sweet potatoes reminded them of the yam that was part of the staple diet in many African countries. The word yam is derived from nyam, nyami, or nyambi, meaning “to taste” or “to eat” in certain African language dialects. Adding to the story, apparently Louisiana sweet potato growers in the 1930s used “yams” as a marketing name for a new orange-fleshed sweet potato cultivar and the name stuck.

One thing I find interesting is that yam was used to describe orange sweet potatoes when the white fleshed ones (which are less common now) would probably more resemble an actual yam, both in appearance and flavor. In fact, in my travels in Rwanda I ate many white fleshed sweet potatoes, as they are now a major staple crop in many African countries. It is also interesting to note that the refugee farmers in our urban farm programs prefer to grow the starchier, less sweet varieties of sweet potatoes, which often complicates things as they can be hard (and expensive) to find.

Whether you cook sweet potatoes or “white” potatoes for your Thanksgiving feast, now you’ll know a little bit about how each of those crops are different…and you’ll at least know that sweet potatoes aren’t yams.

Big Blog on the Block

There’s a new1 blog on the social media block—The Big Blog of Gardening (BBoG). Already it’s a heavy hitter in the gardening social media world. The question is: How may foul balls are hit?

My wife came to me recently saying “Hey! Did you know that your friend Linda Chalker-Scott changed her institution?”
“What?” I said.
“Yeah, she moved to University of Washington. It says right here on this MSNBC article.”
“It’s from the Big Blog of Gardening? What’s that?”
Turns out that the BBoG is hooked into national media and gets consistent play on the home pages of those who go to MSNBC. This is because the BBoG is “now part of the Microsoft Start Program” that places content on the MSN homepage whenever a user logs in.

The originator of the BBoG is not a scientist and in the “About” section of his web page states that he started gardening as a child (like many other of us that had school gardening programs around the country). I also started gardening as a child, volunteered at Descanso Gardens in La Canada, but in my own case I followed up my childhood experiences with a dual major in Botany and Horticulture, an MS in plant pathology, a PhD in plant pathology, and a 30-year career with Cooperative Extension advising and researching in landscape horticulture. These are the typical qualifications for the blog writers at the Garden Professors web pages. Unlike writers for the BBoG, we are the folks who actually conduct research on horticulture and gardening subjects that other people quote and cite.

For us scientists, one of the pitfalls of the BBoG is it’s not a science-based blog. In a blog on pruning, the title proposes to inform how to prune any landscape plant. When you read that article, it just directs you to a link to Amazon.com to purchase a publication of the American Horticultural Society (which is not a science-based organization even though it sounds very much like the American Society for Horticultural Science – the oldest horticultural science society in the US). Rather than cite current research or address the blog title’s topic, the article leads to a product you have to buy to get your information. BBoG posts are full of of links to products available online or to “paid for links” for non-scientific and misleading garden books or other resources.

Broad strokes are used in titles of the blog. For example: “Staking a tree is almost never the right thing to do”. In some ideal world where nurseries grow trees w/o stakes and landscapes don’t require protection from damaging elements this may be true, but this is not the world we live in. Trees grown in nurseries are often staked to facilitate production and shipping. Staking can be used as a protection process on trees that may suffer impact from moving vehicles (these stakes have no attachment to the tree but serve as protective bollards). Titles in some other posts are merely attention getting or serve to promote products – not to reflect accurate horticultural science.

The BBoG often cites Dr. Linda Chalker-Scott, quotes her published work, provides links to her white papers, but doesn’t actually email or otherwise contact the original author. The problem is that often there are peer-reviewed sources by the same author containing this newer information (e.g., WSU Extension publications). BBoG often seems to miss the actual scientific or peer reviewed work but focuses on popular sources such as Fine Gardening or, even worse, Consumer Reports. Consumer Reports is not a legitimate resource for science-based information. (link to Jeff Gilman’s blog post)

Beware the comments at the end of articles on the BBoG as there can be pseudo-scientific information there (using gypsum to create drainage in soils) that goes unrefuted by the article authors. It is important that site administrators approve comments before they are listed, or at least address the misconceptions in a response.

When BBoG stories hit the mainstream media (like MSN) the blog owner does not always mention the original sources of their stories, or the scientists who developed the information: they take credit and reap the rewards of increased eyeballs on their posts and clicks on their advertising links. Wouldn’t it be nice if members of the media could dig a little deeper and find the science-based gardening sites and give them some well-deserved publicity?