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.​

Have you met Evening Primrose's strange cousin – a plant that only blooms after dark?  What could be more dramatic that blooms that open in an instant, right before your eyes?   It's not time-lapse photography, just the mysterious after-dark trick of Oenothera flava (Night Blooming Primrose). 

Thunder Bay gardener Susan Renaud – a Master Gardenener in Training – shared photos and thoughts about the Oenethera flava she grew this year.  "I have one of our Master Gardeners to thank for the unique experience of watching this unusual plant perform this summer," says Susan. "I managed to snap several pictures during its bloom times and was always fascinated how quickly they disappeared when the sun warmed their faces."

Cultivating Night Blooming Primrose
The garden guide on SFGate offers good cultivation advice.  "Night-blooming evening primroses generally prefer full sun and grow best in a bright, sunny spot.  They can tolerate some light shade for a few hours each day, but deep shade compromises growth and flower production.  They tolerate all types of garden soil but prefer sandy, well-drained types.  If your soil contains clay that tends to hold water, add some fine sand at planting time to improve its drainage.  The plants need only an average amount of moisture, although once-weekly watering after setting out new plants can help them get a good start.  Once the primrose has established, avoid giving it too much moisture at the root zone."

Oenothera flava can survive in the northern garden, but low temperatures and a wet spring can be hard on this perennial.  Susan recommends checking the root early in the season.  The offshoots that appear from the root crown often survive, even if the main root dies back.  These root pieces can be potted up to start new plants.

"My NBP grew to a mound of about 8 inches high, with arching leaves and a spread of about 15 inches," Susan reports.  "The bloom stems arched up at about 10 inches. There were about 24 blooms over summer." 

Although the blooms of Oenothera flava fade equickly, there is a magic in their coming and going.  "I, for one, am happy to have had the opportunity to witness this beauty in action," Susan says.
​You can see it too, but watching this video.

Fine Gardening magazine describes Chelone obliqua as a "great mid-border plant."  This native wildflower loves moisture, growing well in partial-to-dense shade with moist soil.  It will even grow in full sun if the soil is soggy, making it a plant to chose for a bog garden.

The Missouri Botanical Garden – another go-to site for solid plant information  – describes Chelone as "a stiffly erect, clump-forming Missouri native perennial which typically grows 2-3' tall and occurs in moist woods, swampy areas and along streams.  Hooded, snapdragon-like, two-lipped, deep rose flowers appear in tight, spike-like terminal racemes from late summer into autumn.  Flowers purportedly resemble turtle heads."  Apparently the plant's name comes from "the Greek word chelone meaning tortoise, in reference to the turtlehead shape of the flowers."   The epithet (the second part of the Latin name) means "lopsided or oblique."

Chelone is, according to Todd Boland of the MUN Botanical Garden in Newfoundland, one of only a handful of ornamental plants that "are purely North American natives."   Chelone is not as well known as our other natives – Phlox, Rudbeckia and Echinacea – but this plant is becoming more popular.

In his excellent factsheet, Turtleheads–The Genus Chelone, Boland explains that there are only four species in the genus Chelone.  

Chelone glabra is the white flowered species.  Chelone obliqua and Chelone lyonii ​both have pink flowers, but vary in their leaf shape and their native range.  Boland's factsheet helped me examine the characteristics of the leaves on the Chelone in my garden and I am pretty sure it is Chelone lyonii.  A beauty by any name!

Click each map to view the US Department of Agriculture plant profile. ​

Chelone is identified as hardy to Zone 4, making it marginal in the northern garden.  My Chelone did come with a warning about hardiness, but I am hopeful that with leaf mulch and reasonable snow cover, this little turtle will come back again next year.

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.