I've mulched with leaves for many years.  I discovered their value when I gardened on a steep south-facing slope where the soil would warm enough to thaw, and then freeze again. This can spell certain death to many shallow-rooted plants.  I've come to think of leaf mulch as my secret weapon.  

In the north, our winters seem to be characterized by more frequent temperature fluctuation. I believe this is a marker of climate change. Applying leaves as a mulch provides a layer of insulation while allowing plants to breathe. Under the leaves, the soil temperature remains even and soil heaving is reduced.

Have you noticed how hosta leaves slide into a soft brown skirt that gracefully covers the plant's crown? This is nature's leaf mulch.  I top up this covering with more small or deeply-lobed leaves.  Manitoba maple leaves – which are abundant in my neighbourhood – are ideal.  ​​​

When should you mulch?
It's best to mulch after the soil freezes. The goal is to keep the soil frozen longer, allowing plants to slumber on for the whole winter with their roots frozen and resting, even during  thawing periods.  I always wait for a hard freeze before I mulch, but weather conditions dictate when this fall chore is best done.  It's not much fun to be outside in the freezing rain mulching garden beds.  If light snow has fallen, you can still mulch. Work leaves around the plants and in wind-swept areas, anchor them with spent plant stalks or evergreen boughs.  When the snow comes – or even a crisping frost – everything will be held in place.

About getting leaves ...
I live in a treed neighbourhood.  Leaves are everywhere.  This year, as my neighbours raked, I asked them to save their leaves for me. 'No need to bag them,' I said. 'I want them for my gardens.' One brought me a huge tarp full. Another leaned a mattress bag full of beautiful dry leaves by my front steps. Marvelous.

Come spring, the leaf mulch will find its way, a little at a time, into my composter.  With luck, they will also go into a bin for fine shredding with a weed-whacker, only to return as a finer, weed-blocking mulch for summer.  Yes, leaves are definitely my secret weapon.​

I remember the day in May I dug up all the perennials in a 30 foot bed in my country garden.  Even as a relatively new gardener, I knew the soil in the bed was too sandy.  The plants were struggling and would never be their best without more nutrients.  I remember the hard work of shovelling wheelbarrow loads of sand out of the bed and replacing it with load after load of composted sheep manure and peat moss.  By supper time, the plants in place. 

Looking back, the biggest lesson I took from that gardening effort was to never take soil for granted.  It needs care and protection, just like all other things in the garden.  It's a lesson I am thinking about today.

As the Food and Agriculture Organization of the United Nations declares that "soils have been neglected for too long.  We fail to connect soil with our food, water, climate, biodiversity and life.  We must invert this tendency and take up some preserving and restoring actions."

The UN initiative Global Soil Partnership has taken on the task of activating concern about soil. 

They remind us that soil is "the reservoir for at least a quarter of global biodiversity, and therefore requires the same attention as above-ground biodiversity.  Soils play a key role in the supply of clean water and resilience to floods and droughts.  The largest store of terrestrial carbon is in the soil so that its preservation may contribute to climate change adaptation and mitigation.  The maintenance or enhancement of global soil resources is essential if humanity’s need for food, water, and energy security is to be
met.

While the Global Soil Partnership pursues soil research and education, what can we as individual gardeners do? 

We can start by learning more about the soil we depend on.  We can understand its composition and what it takes to keep it healthy  – right in our own backyards.

And the very best resource I know is an excellent documentary directed by Deborah Koons Garcia, called Symphony of the Soil.

This beautiful film will change how you see soil.

• View segments of the documentary
• Watch the full documentary on Farming Secrets

World Soil Day closes 2015 as the UN International Year of Soil – officially – but for each of us, it is a beginning.  A chance to think about the soil in our gardens and under our feet.

I think DaVinci had it right.  We understand little about the soil of the earth, the essential substance on which we all depend.  Or at best, we take the earth beneath our feet for granted.  Nothing will underscore this more than viewing the newly-released documentary, Symphony of the Soil. 

This compelling and positive film was featured as part of the Docs on Bay film series in Thunder Bay earlier this month.  The film's maker, Deborah Koons Garcia, attended and discussed the film's message of stewardship .  As a gardener committed to composting and organic methods, I couldn't help but find Garcia's perspective engaging.

If you have not seen the film, find a way to do so; you will be moved and encouraged.  The DVD (available online) is a worthwhile purchase.  Take a moment to view the trailer...

“Unfolding with gentle joy and an unexpected beauty, this ode to the miracle of the Earth’s topmost layer gives us a newfound respect for the ground beneath our feet.”
― New York Times Critics Pick

At the Thunder Bay screening, Garcia explained pieces of video not included in the final cut were too valuable to lose.  She in sharing them online  as 'Grace Notes'  and 'Sonatas of the Soil' (to continue the musical metaphor).

One of my favorite 'Grace Notes" is the piece with Dr. Vandana Shiva, a physicist-turned-activist in India.  Her wisdom about fertility gives us something important to ponder as we step towards another growing season.

If you are reading this post as an email message, you're missing the video clips.  Come to The Blog Bouquet to view them.

I am about to do something radical. I'm going to plant seeds now – in the middle of winter – and place them in the snow to germinate. It's called winter sowing and, after listening to local gardener Lois Kennelly explain the basics, I'm convinced it's worth a try.

The goal, Lois explains, is to create mini greenhouses from plastic containers saved from fruits and salad greens. The containers are filled with moistened potting soil mixed with perlite or with a commercial seeding mix. (Do not use a purchased soil mix that contains fertilizer or a water retention product.) Seeds are sown into each container and covered with soil to the required depth.

Labeling the seed type is important; duct tape marked with a permanent marker works well. With covers securely in place, the containers are placed in the snow under Mother Nature's care.

The winter sowing method is simple and low cost.  It requires no grow lights or expenditure on extra hydro.  It is ideal for those of us with little indoor space to spare for seed starts.  And it's a positive way to leverage our long northern winters!

Why does winter sowing work? 
Many seeds only become viable after exposure to chilling temperatures. The winter months naturally provide this vernalization, this necessary cold-temperature treatment that promotes flowering.

Winter sowing is an ideal germination method for perennial and hardy annual seeds.  It is especially effective for herbs such as parsley and oregano, cold germinating vegetables like spinach, chard and kale, alpine species and biennials like hollyhocks which need two seasons to produce flowers.

What seeds should you choose?
Trudi Davidoff, who is credited with discovering winter sowing, offers advice on how to read the clues given in seed catalogs. Terms such as "Needs Pre-chilling (freeze seeds, refrigerate seeds, stratify for x amount of days or weeks), Needs Stratification, Will Colonize, Self-Sows, Sow outdoors in early Autumn, Sow outdoors in early Spring while nights are still cool ..." are all clues that the seed type is appropriate for winter sowing.  You can find much more advice about seed selection at the excellent website, WinterSown.org.  Do remember to consider your hardiness zone when choosing seeds. 

For easy-to-follow steps and illustrations, I recommend reading Kevin Lee Jacobs' Winter Sowing 101. You'll note that Kevin uses plastic milk jugs as mini greenhouses.  Many plastic containers will work, as long as the plastic is sturdy enough to support the weight of soil and plants. Lois recommends only using clear plastic containers to allow maximum light to reach the seedlings.

Winter sowing does require a little organization; not all plants need to be sown at the same time. Kevin's updated post on A Garden for the House offers good advice on the best time to sow specific plants.

Winter sowing is definitely something new for me.  Like any new gardening approach, it calls for a little research and a little experimentation.  The USDA describes this method as a way "to foster a naturally timed, high percentage germination of climate tolerant seedlings."  What could be better for our northern gardens?  Why not give it a try?

Visit WinterSown.org for comprehensive lists of perennials, hardy annuals and vegetables suitable for winter sowing.
Browse or post a question on the Canadian Winter Sowing forum on GardenWeb.com.
What is your experience with winter sowing?  Please share in a comment.

In 2000, the map was updated, using more recent climate data from across Canada.  Plant survival data for indicator trees and indicator shrubs (the northern and southern extremes where selected species can survive and reproduce successfully), the effect of elevation, and climate-change models were also used.

What emerges is a new distribution of zones.  According to the Canadian Forest Service, "the hardiness index has declined or remained stable in eastern Canada and has increased in western areas."

You can view the interactive map at Environment Canada to gain insight on your zone.

How do zone changes affect the way we garden?
Here are a few thoughts ...

• More than ever, it's important to investigate the known hardiness of perennials, trees and shrubs before you buy.
  
• Try to buy cultivars that have been grown in northern temperatures. Divisions from a friend's garden may be more hardy than an imported plant.
  
• Explore the micro-climate options in your own garden. Do you have sheltered places where you can plant cultivars that may be tender?
• Start a plant nursery. While they take time to mature, you can start many perennials from seed. The plants you grow yourself in a corner of your garden will be tough, ready to take on the things our zone can throw at them.