Thinking About Snow

“Now the snow can blow,” said Glenn as he came in from doing the last of the chores. He tucked away all the breakable containers and puts plastic bags over some because he uses them to weigh down his pool cover.

Glenn has the breakable pots tucked into black garbage bags to keep them from getting wet and going through the damaging freeze-thaw cycle.

It’s a grey November day, the only colour a blaze of orange from the pretty summertime lime Berberis thunbergii ‘Aurea Nana’ in my front yard. This is the beauty that never gets more than a couple of feet tall and can be trimmed, if you are of a mind, into a well-behaved ball that stands out incandescently in the garden. I have three of these barberries. The largest is about seven years old. The other two are at least three years old and still very small, under 12 inches – they seem to take a long time to establish here in Manitoba. I can’t wait until they are all big enough to be showstoppers in the garden in summer and in fall.

The brilliant little barberry that blazes in the grey November day.

It always makes me happy to see them, although I have never seen them bloom or produce berries. But their smiling foliage is enough.

Snow Days

The other morning, as I left the house to go to my office, I noticed a scattering of white marbles all over the lawn. It looked as though we had been visited by a herd of albino bunnies over night, but it was just hard little lumps of hail. It keeps trying to snow, to do its natural thing here, but not just yet.

I read the other day that, before a cloud can produce rain or snow it must produce ice. The ice droplet forms around a nucleator (a particle that becomes the nucleus of a group of water molecules, in this case). Sometimes the nucleator is a speck of dust or a mineral, such as salt, but now it is believed that, more often, the nucleator is biological in origin, often a bacterium called Pseudomonas syringae, a plant pathogen the causes bacterial speck, a nasty disease, on tomato plants.  It can also attack canola and other plants.

Dust and salt particles work as nucleators at very cold temperatures whereas the biological catalysts do their job about around or just below 0 degrees C. Nucleation is also what allows a frog to freeze into a “frogcicle” (see Ten Neat Things, November 4, 2011) and it’s the same thing that causes a diet cola to explode when combined with Mentos candies).

Many of the bacterial nucleators are pathogenic in nature and falling to earth can break the walls of the plant cells they feed upon. In addition to tomato speck, Pseudomonas syringae can also cause frost damage to plants. On the other hand, a little scientific manipulation can also make the bacteria useful in protecting citrus crops from frost damage.

Bacteria may be implicated in drought

Without the biological vectors, rain has to get as cold as -40 C before it falls. The bacteria, however, cause ice to form at a much higher temperature so that rain can fall in temperate and even hot regions.

A woman named Cindy Morris, an Agriculture Plant Pathologist at the French National Research Institute, has proven that bacteria are good at making water freeze. She cooled a tube of water to about -6 degrees Celsius, without freezing it. When she dropped some bacterial culture into the tube, the water froze completely in less than two seconds.

Some scientists postulate that a lack of bacteria can create drought. If land is too closely grazed, for example, there is no host for the bacteria and hence no rain.

This hypothesis about bacteria and rain has been around for about 25 years, but it has only recently that there has been a renewal of interest and study on the topic of what is now being called bioprecipitation.

It is part of the wonder of gardening and biological life that never ceases to capture my imagination.

November 6, 2011


8 thoughts on “Thinking About Snow

  1. Fascinating article & I love the colour of the Barberry leaves – nice contrast to the many green leaves that one usually finds on plants.

  2. Granny says:

    I second that. Fascinating article. I read this and I think of balance: The plants that naturally inspire a new take on holding down the pool cover when swimming season is over; and on a larger scale, the impact of yet another space, the land, on the changing seasons and precipitation. It all balances out.

  3. beth says:

    Lovely, Dorothy — color speaks to the soul, doesn’t it?

  4. minervasgardenwriter says:

    We don’t have snow yet, but we did have our first somewhat killing frost of the fall, and I went out before and covered containers and salad greens beds.

    Thank you for stopping by my blog and liking my post–it is much appreciated! (I went to school up in Alberta!)

  5. […] We certainly ran the gamut as far as weather was concerned this past week here in Calgary – we went from extremely damaging high winds and balmy plus-teen temperatures to a raging, snow-filled winter storm all within 72 hours.  A skiff of pebbly snow and ice is now firmly encrusted on the ground, caking over the slumbering (and probably dessicated)  forms of my perennials and shrubs.  A timely article by the The Gardening Canuck, Dorothy Dobbie, has got me thinking about how snow (and rain) is formed:  apparently, the process may be linked to another bacterium, this one called Pseudomonas syringae.  Along with dust particles, P. syringae acts as a nucleator around which the rain drops or snow flakes are constructed – and researchers are realizing that they may be able to manipulate the bacterium to relieve drought, for example, or to reduce the potential for frost damage on tender food crops.  (A known plant pathogen, P. syringae can be a bit of a nasty beast as well, so extra study and care must be undertaken to keep it from harming plants instead of helping them grow).   Read Dorothy’s post about bioprecipitation and its implications here. […]

  6. […] Thinking About Snow ( […]

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