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.​

What can provide more pleasure, early in the season, than making the rounds of the nurseries and big-box stores to source out new plant varieties and old favourites.  Time and time again, however, I find myself asking the same two questions:
Why are we seeing the same clematis varieties year after year?
Why are so many offered which are not guaranteed to survive in our Zone 3 gardens?

Group B (2) Clematis

• large-flowered hybrids, single and double
• bloom in early summer and occasionally re-bloom in late summer
• flower on previous year's growth

This group is the least reliable and should be avoided.  Some examples are:

• 'Duchess of Edinborouqh'
• 'Multi Blue'
• 'Dr. Ruppel'
• 'Henryi'
• 'The President'
• 'Elsa Spath'
• 'Niobe'
• 'Nelly Moser'
• 'H.F. Young'

You will recognize several of the above selections since they regularly appear of big-box stores and some nurseries. Do not be tempted!

Want to learn more?
Most of the cultivars mentioned are profiled on the Royal Horticultural Society online plant guide.  It is an excellent compendium of plant information, but always confirm the Canadian hardiness of plants to be sure of success in our colder zone.

I admit it.  I've changed into a vegetable gardener. 

Oh don't get me wrong  – I still love to grow flowering perennials and I couldn't be without my pots of sunny dahlias, petunias and fancy coleus.  But this planting season, the 'Call of the Edibles' was stronger then ever. 

In the garden centre, I found myself gravitating to the vegetable starts;  I kept my ears open for 'giveaway ' vegetable plants from friends and neighbours.  These are all signs of 'The Change'.

I am like many gardeners who are interested in the potential of urban agriculture.  I want to see what can grow in a city yard – given enough sunshine, water and attention.  In June I felt real excitement when I set up my carefully-stored straw bales for another season of this alternative growing method.

Yes, typically you have to replace the bales each season.  Since farmers make straw in the late summer and it's hard to find in the spring, I bought straw bales last fall and covered them with a tarp to keep it dry over winter.

Now, the conditioning process is key to straw bale success,  Once again I followed the regimen of fertilizer inputs to get the bales 'cooking'.  This decomposition within the bales gives off heat and supports great veggie growth. (See the Straw Bale Gardening page) 

But there were challenges. 

It rained and rained.  It stayed cold.  It rained some more.  I wondered if the the fertilizer was just washing out of the bales; I worried that the bales would not heat up properly.  I wondered when I could plant my tomatoes and cucumbers – both heat-loving crops – in the bales. 

Like every gardener, I had to make a call and get those plants in!  I was nervous the bales weren't ready, but when I saw mushrooms on the sides of the bales, I knew all would be well.  As straw bale guru Joel Karsten says, the conditioning always works out in the end.

Here we are a good 3-4 weeks later and the tomatoes are growing tall, setting blossoms and fruit.  They are doing well.

In fact, the weather this season was typical of the cool, protracted spring that climate change has dealt our part of the northern hemisphere.  Planting out comes late in our region.  I have to hope mild fall weather will hold as it has in other years – another feature of our shifting growing conditions.  After all, vine-ripened tomatoes is the goal.

What I've learned this year...
Healthy tomato starts can have a good-sized root mass.  To ease the plant into the bale without damaging those tender roots, I learned you can create a cavity by pulling out some straw, working until you have a generous hole.  I added potting soil and  10-10-10 fertilizer to the hole before planting.  (Thanks to Master Gardener Hazel B for demonstrating this trick.)

Metal fence posts are useful for holding the bale row together and for running additional wire to support tomato plants.  Wire fencing makes a good trellis for cucumbers.

A bale garden is essentially a raised bed.  When we had intense rains and my backyard flooded overnight, my tomato plants were high above the water.  The same wouldn't be true had they been planted in a conventional garden.  I read about this benefit; now I believe it.

So there you have it – Season 2 of the straw bale garden.  So far so good.

In the world of horticulture, there have been many giants – landscape designers, plant breeders and teachers.   I am grateful for meeting my 'giant' in horticulture – Dr. Linda Chalker-Scott – during her April visit to Thunder Bay.   As I've worked in my garden this season, I've reflected on and applied the advice she shared with gardeners in my community.

I want to report on a technique that Dr. Chalker-Scott champions – the bare root transplanting of shrubs and trees.  

Many landscapers will consider this controversial, but I think it is beneficial.  I've tried it with newly-purchased potted shrubs and with a shrub that needed to be moved.  From what I can see, these plants are doing well, thanks to lots of rain, cool days and this transplanting method.

I needed to relocate my dwarf willow (Salix integra ‘Hakuro-nishiki Dappled Willow’) to a shadier, more moist location.  I dug up the willow and was shocked to see the root ball looked exactly the same as it did when I planted it a year ago.  The root mass was the shape of the pot it had come in; they had not spread into the soil at all.  How I wish I had a picture to share!  

Here's how I used the bare root transplanting method to remedy the situation. 

I placed the shrub in my wheelbarrow and gently washed the soil from the roots.  I checked the roots for structure and health.  I pruned away some of the bound up roots and untangled the rest.  I dug a shallow hole in the new location, and without amending the soil at all, I arranged the shrub with its roots radiating out like the spokes on a wheel.  I covered everything with soil, taking care that the shrub was planted at the same level as before, then watered well. 

To my amazement, the willow has shown no signs of stress; instead, there is plenty of new growth.  I know that below ground, my willow is well-supported and its roots have ample opportunity to draw nutrients from the soil.  I am keen to see how it progresses this season and beyond.

On to the planting of newly-purchased shrubs. 

My neighbour asked me to help with the placement of three new shrubs.  Armed with my new experience, I felt pretty confident we should use the bare root method.  As we removed the purple-leaf sand cherry (Prunus × cistena) from its pot, I could see that the roots had already begun to curl and harden within the pot – not a good sign.  Left as is, the woody, curled root would likely continue to grow in a circular direction around the root ball.  This is how shrubs and trees can be girdled by their own roots. 

I pruned back this circling root and proceeded as before – planting in a shallow hole, watering in with the water left from the root baring process, and covering over with soil to the correct depth.  Voila, a happy shrub!

You can review the bare root method in more
detail in Dr. Chalker-Scott's excellent slideshare,
"Take It All Off" (file download below).

Dr. Chalker-Scott, the Extension Urban Horticulturist at Washington State University, was a delightful guest.  We toured some of our northern sights. 

Fortunately for gardeners this talented teacher shares her advice freely on her website, The Informed Gardener, and in her books.  As well, you can find her among the horticulturists at The Garden Professors.  Her useful perspective on landscape plants will get you doing things differently.  There's still time to plant a shrub or two this season.

Gardeners in the northwest are gathering this weekend – not to plant, but to listen and learn.  Dr. Linda Chalker-Scott – one of horticulture's best 'myth busters' – will be speaking in Thunder Bay  this Saturday, April 30.

Dr. Chalker-Scott, Associate Professor of Horticulture at Washington State University (WSU), is a champion of the real science behind good gardening practices.  And in explaining the science, she busts a lot of myths about fertilizers, mulches, planting practices and how plants work.  There are dozens of gardening topics and the associated myths listed on her webpage, Horticultural Myths, at WSU.  Each short article will leave you wiser for the reading.

For example, The Myth of Wilting Leaves, addresses the commonly-held belief that leaf wilt is "an indicator to increase water application."   In reality, says Dr. Chalker-Scott, watering wilted plants can make things worse "if lack of soil moisture is not the underlying cause of wilt." 

Stands to reason, right?  But why?

The fact is, reports Dr. Chalker-Scott, "Leaf wilt can result from a number of stresses in the soil environment, many of which lead directly or indirectly to water deficits in the leaf.  A common cause of leaf wilt in urban environments, especially sites with compacted, poorly drained soils, is root anoxia.  Soils without sufficient pore space are deficient in oxygen which severely impacts root function.  Roots, like any other living tissues, require oxygen for survival; since they are not photosynthetic they rely on oxygen from the soil or from above-ground parts of the plant. Excess water will fill soil pores and eliminate gas exchange.  Without enough oxygen, root function shuts down and water uptake ceases.  Leaf transpiration, however, continues and eventually leaves will wilt as their water content decreases. Ironically, the leaves suffer from drought stress even though soil moisture is more than adequate!"  I encourage you to read more detail in the article. 

I love the way this scientist ends her articles with "The Bottom Line" – a summary that gives the remedy and/or practical advice.  For wiliting leaves in plants, trees and shrubs, the summary points include:

• Be sure to assess soil conditions before irrigating wilted plants.
• If soil is wet, try to aerate through the root zone.
• If soil is chronically wet, consider installing a French drain or other passive means of drainage. [A French drain is a trench filled with gravel or rock or containing a perforated pipe that redirects surface water and groundwater away from an area.]
• Alternatively, select trees and shrubs adapted to wet conditions.

There's another "bottom line", I'd say. The science behind good gardening practices should guide our gardening efforts.  Fortunately for us, explaining the science is Dr. Chalker-Scott’s passion.