Northern Shade Gardening

The perennials in my garden with semi-evergreen leaves are still looking good, despite the below freezing temperatures,  but the – 35°  C (-31 ° F) temperatures that will come later this winter will test their cold hardiness. Alternating cold and warming spells  can stress perennials, with the freeze thaw cycle.  We usually get consistent snow cover from December to April, which helps to insulate the plants. I’ve found that adding a layer of deciduous leaves over them also helps insulate the perennials from a cold zone 3 winter.

Just before the snow comes, the leaves from the trees overhead cover the garden. The trees do a pretty good job, and I assist by helping to fill in the garden sections that are missed, covering the perennials up with the fallen leaves. All of the perennial crowns benefit from the winter leaf mulch, and the plants still holding onto their leaves will appreciate the above ground protection too.

Helleborus Ivory Prince leaves before covering

Here is the fantastic foliage of Helleborus ‘Ivory Prince’. These are semi-evergreen, and will stay on the plants until spring, but that means that the severe temperatures, and drying winds can damage these leaves. Last year, the leaf cover kept the Helleborus in excellent shape until April, as well as protecting the crowns.

Helleborus Ivory Prince under fall leaves

A thick leaf pile collects under the willow tree, and here it is on top of the Helleborus. I threw some  extra armfuls over them. The slender willow branches placed over top help keep the leaves in place when the wind blows.

Heuchera 'Mint Frost' in fall leaves

Heuchera (coral bells) can heave out of the ground over winter, but the extra leaf layer helps to insulate them. I had no heaving of these perennials last winter.

Heuchera 'Plum Pudding' under fall leaves

The Heuchera ‘Plum Pudding’ (coral bells) contrast with the deciduous leaves. You can see the wonderful burgundy coloured stem on these perennials, while the purple and silver colour of the leaves is even stronger from the cold temperatures.

Campanula under fall leaves

In the above photo, the Campanula (bellflowers) are partially covered with leaves. Most of the bellflowers I grow are very hardy in zone 3, and survive fine without leaf cover, but the extra layer in the garden won’t hurt them.

When the snow melts in spring, and the temperatures get warm, I remove the protective leaf cover from the garden beds. This is the fun part of spring gardening, pulling back the leaf mulch to see what is growing underneath. Some of the leaves have broken into small pieces, and will decompose into the garden soil, forming part of the mulch. The rest is set aside to decompose and be added back later. The perennials will use the good nutrients in the leaves.

Although we’ve had  a few nice weeks, the temperatures are consistently below freezing at night. The willow tree, which hangs on the longest, is losing the last of  its leaves. While the intricate pattern of branches is outlined overhead, underneath the fallen leaves will blanket the garden, and help protect the perennials.

The tall flower wands of Actaea are very dramatic as they open in the fall garden. They rise above the other plants and look very fresh as many other perennials are going into decline.  Actaea (used to be Cimicifuga) (bugbane) are a great solution if you need a tall plant for a shady border. I have four groups of these around the garden, and the showy flowers at eye height or above add rhythm and beauty to the garden.

These perennials used to be classified as the genus Cimicifuga, but now they are grouped with the other short Actaea. Beyond the genus change, I find the classifications a little confusing, as many of the cultivars such as ‘Atropurpurea’ are listed under different species. Also, A. ramosa seems very similar to A. racemosa.

Actaea ramosa (bugbane) flower buds

The flower wands of these tall Actaea ramosa are long and thin, with many buds. The initial buds have a purple colour, and are attractive before they even open. In my zone 3 garden, these flamboyant perennials start flowering towards the end of September. I have some that flower with only an hour or so of direct sun a day.

Actaea racemosa (bugbane) flower buds with conifer

Here are the buds of Actaea racemosa. These plants are  over 2 metres (6 ft) tall, so I was shooting up as I took the photo, and they are displayed against the green conifer background.

Actaea racemosa flowering

The open Actaea racemosa flower wand is whipping around in the wind. Because it is so tall, it was swaying a metre (3 ft) to either side. That little guy hung on to the tip the whole time. You can see as they open, that the flowers are fluffy white. The central stalk has opened first, and the side wands are still in the bud stage. Although they are tall, the stems don’t need staking. Even after swaying in the wind, the 2 m (6ft) stems are upright, although the flowers on top can have a natural curve.

Actaea racemosa (bugbane) flower stars

Actaea racemosa has a sweet scent. Some Actaea have an unpleasant smell, so I was pleased when this one bloomed. The pleasant scent actually carries for a few metres, even from just one bloom. In the above closeup, you can see how they form starry clusters on the ends of the wand. The long, thin flower clusters add emphasis above the foliage, like exclamations marks in the garden.

Actaea (bugbane) leaf with purple edge

The foliage of these forms of bugbane makes an attractive backdrop for other perennials. The leaves have a purple tinge to the edges. There are other varieties that have an even stronger all over purple colour to the leaves. I especially like how the leaves come out in layers. It reminds me of the cloud pruning of an evergreen. The central stalk has a distinct purple colour too.

Bugbanes like moisture, but in the shade they seem to do fine. I would be careful planting it in sun, as I had one  in a pot waiting to be planted that dried out very quickly, with the leaves turning crispy.

I have some Actaea simplex that are also tall, but the plants have a different form, and they bloom later. A. simplex bloom too late for zone 3, as the frost gets them before the flower wands open.

Actaea are an excellent plant for the back of the shade garden. They have good looking leaves, a dramatic form, and eye catching towers of flowers in the fall. As most perennials grow tired and start to fade back, these plants will put on a great final show.

Phlox paniculata 'David's Lavender'

The flowers of Phlox paniculata ‘David’s Lavender’ are a pinkish lavender color with a white eye. I planted some of these tall phlox in spring, and the plants started flowering at the end of August. The blooms on this perennial are very attractive, and perk up the part shade garden area of blues and whites.

These are supposed to be as mildew resistant as the white Phlox paniculata ‘David’. I don’t have many problems with my phlox, but mildew resistance is a great trait, and so far these  seem healthy. It will be a better comparison next year, when they’ve grown in my garden for a season. It’s hard to tell exactly how a perennial is going to do, when it just came out of a pot at the beginning of the year.

Phlox paniculata 'David's Lavender' morning light

The flower colour looks great. It is midway between a lavender and the phlox magenta. In the morning when I look out of my bedroom window, they appear more lavender coloured, just like the second photo. During the brightest light of the day, they have more of the phlox magenta showing, like the first photo. I have them planted next to some white Phlox paniculata ‘David’ and behind some Campanula ‘Summertime Blues’, which have purplish blue bells. A white flowered Hydrangea will be going in behind them, replacing a Viburnum that was planted too close to the house.

My David  in this area opened shortly after  David’s Lavender. Since I planted the new phlox this season, I won’t know until next year what the natural bloom time of David’s Lavender will be. David flowers late in my garden usually starting about the middle of August, but this year it started at the end of August.

This is a part shade garden bed,  so phlox does well here. The  colour of David’s Lavender brightens up the white and blue flowers. In the photo below, You can see how each set of petals on David’s Lavender stand out because of the white eye, compared to David on the right. I’ll be adding more David’s Lavender to this group next year. These are a showy perennial that look good with the late summer flowers.

Phlox paniculata 'David's Lavender' and 'David'