How to Prepare Perennial Beds for Winter in Saskatchewan

Fall can make you feel like we've got a long list of things to do before winter actually gets here. Then, where do you even start??

Should you cut everything down? Do you need to mulch every perennial? Should you keep watering after the first frost? What about all those fallen leaves?

The good news? Preparing your perennial gardens for winter is much simpler than doing a complete fall cleanup.

In fact, if you clean your beds too thoroughly, you can remove some of the natural protection that your garden needs.

Here (in Southern Saskatchewan) our perennial gardens have to handle the cold, drying winds, inconsistent snow cover, and temperatures that can fluctuate considerably (-20 to +15 in a single day). The goal of our fall garden care is not to keep your plants warm, but to help them enter dormancy healthy and protect their roots and crowns from unnecessary stress.

Here is how to prepare your perennial beds for a Saskatchewan winter.

Know Before You Start

Remember, perennials are designed to go dormant.

Dormancy is essentially the plant's winter rest period. As days get shorter and temperatures get cooler, hardy perennials naturally begin preparing themselves for winter.

You do not need to force this process.

Here (southern Saskatchewan), our first fall frost typically arrives around mid-September (although it's been known to arrive a lot earlier as well). Just because it's froze, does not mean you need to run outside the following morning and cut your entire garden to the ground.

Lots of hardy perennials tolerate frost very well.

Plants with healthy green leaves can continue producing energy whenever conditions allow. That energy is stored in the roots and crown of the plant and will help support growth the following spring.

Instead of choosing a particular date for your fall cleanup, watch the plants themselves.

When foliage has naturally yellowed, browned, collapsed, or been killed by repeated hard frosts, you can decide what should be removed and what should stay.

Step 1: Start With a Garden Health Check

Before cutting anything back, you will want to walk through your perennial beds and look closely at your plants.

Your first priority should be removing anything that could create problems next year.

Look for:

• Diseased foliage
• Heavily spotted or mildewed leaves
• Rotting plant material
  
• Damaged or broken stems
• Weeds that have gone to seed
• Annual weeds still growing between perennials

Diseased plant material should be completely removed from the garden rather than left in place. Leaving this infected plant material can give you more problems next year.

Some fungal diseases can overwinter on infected leaves and stems. Removing that material reduces the amount of disease present when conditions become favourable again next spring.

Healthy plant material is different. It does not automatically need to disappear simply because winter is coming.

Step 2: Decide What to Cut Back

One of the most common questions we hear in fall is:

"Do I cut all my perennials down?"

No.

Some perennials benefit from being cut back, while others are perfectly fine left standing until spring.

Good Candidates for Fall Cutback

Plants with foliage that becomes wet, mushy, diseased, or badly collapsed are usually good candidates for fall cleanup.

You can also remove foliage from plants that have had significant disease problems during the growing season.

When cutting back, you generally do not need to cut directly against the soil. Leaving a few inches of stem makes it easier to remember where the plant is located in spring and avoids unnecessary disturbance around the crown.

The crown is the area where the stems meet the roots. For many perennials, protecting this area is important for winter survival.

Perennials You Can Leave Standing

Many sturdy perennials can stay in the garden throughout winter. 

Plants such as ornamental grasses, coneflowers, sedums, rudbeckia and other strong-stemmed perennials can provide valuable winter structure.

Leaving some plants standing has several benefits.

Their stems can help trap snow around the garden. Snow is one of the best natural insulators available to Prairie gardeners.

Seed heads can also provide food for birds, while hollow stems and plant debris can provide habitat for beneficial insects.

And there is another benefit that is easy to overlook.

Your garden can still look beautiful in winter.

Seed heads and ornamental grasses covered with frost or snow give the garden structure during a season when most plants are dormant.

You can always complete the cleanup in spring.

Step 3: Don't Stop Watering Too Early

This is particularly important for us on the Prairies.

Even though Fall may feel cool, that does not necessarily mean the soil contains enough moisture.

Southern Saskatchewan frequently experiences dry conditions and strong winds. Plants that enter winter severely dehydrated can be more vulnerable to winter injury.

Established drought-tolerant perennials may need very little supplemental water, but pay particular attention to:

• Perennials planted this year
• Recently divided or transplanted plants
• Plants growing in exposed, windy locations
• Beds near buildings where rainfall may not reach the soil
• Gardens that have experienced a particularly dry fall

Water deeply rather than giving the surface a quick sprinkle.

Deep watering encourages moisture to reach the root zone.

Continue monitoring soil moisture until the ground begins to freeze. If the soil several centimetres below the surface is already moist, you do not need to add more water simply because it is fall.

The goal is moist soil, not soggy soil.

Step 4: Be Careful With Heavy Clay Soil

Lots of us have to deal with heavy clay soil. Don't know if you have heavy clay? Here are some guidelines:

• Does it get really sticky when it's wet (lose your boots sticky)?
• When it's dry, do cracks open up that you could fall through?
  

Clay soil is not necessarily bad soil. It can hold nutrients and moisture very well. The problem occurs when drainage is poor.

Perennial crowns sitting in cold, saturated soil can be vulnerable to rot.

If your perennial beds stay wet for long periods, adding a thick layer of material directly over the crowns can sometimes make the situation worse.

Rather than trying to dramatically change clay soil in one season, improve it gradually with organic matter such as compost.

Avoid repeatedly digging or walking on wet clay soil. Working clay when it is very wet can compact it and damage its structure.

If a particular section of your perennial bed consistently collects water, drainage may need to be addressed rather than simply adding more mulch.

Step 5: Remove Weeds Before Winter

Fall is a good time to deal with the general weed population that's established throughout the summer.

Removing perennial weeds now means fewer established plants competing with your perennials next spring. Competing weeds will steal nutrients and soil moisture from the plants you do want to show off.

Pay particular attention to weeds that are producing seeds. One weed allowed to scatter seed throughout the garden can become many weeds next year.

Remove as much of the root system as practical when dealing with perennial weeds. 

Just be careful when digging around established perennials. You do not want to damage their crowns or roots while trying to remove a weed.

Step 6: Add Compost If Your Soil Needs It

Fall can be a good time to add a light layer of compost to perennial beds.

Compost adds organic matter and will gradually help improve the soil structure (good soil structure = good plant growth).

This is particularly helpful for Prairie gardens with heavy clay soil.

You do not need a huge amount. A light layer spread over the soil surface is enough. Soil organisms and natural freeze-thaw processes will gradually incorporate organic matter into the upper soil layers.

Keep heavy piles of compost away from the crowns of plants.

More is not always better.

Step 7: Mulch at the Right Time

Mulching is one of the most misunderstood parts of winter garden preparation.

Winter mulch is not primarily intended to keep your plants warm.

Its job is to help keep soil temperatures more consistent.

This matters because repeated freezing and thawing can cause soil movement. In some situations, this can push shallow-rooted or newly planted perennials upward, exposing their roots to cold and drying.

This process is sometimes called frost heaving.

Don't Mulch Too Early

If you are using mulch specifically for winter protection, wait until the soil is cold and beginning to freeze.

Applying a heavy insulating layer while the soil is still warm can delay the natural freezing process.

For Southern Saskatchewan, the calendar date will vary considerably from year to year. Watch the weather and soil conditions rather than automatically mulching after the first frost.

What Can You Use?

Suitable winter mulch materials include:

• Clean straw
• Shredded leaves
• Loose, dry leaves
• Bark or wood mulch already used in the bed

Avoid packing a thick, wet layer directly against plant crowns.

Loose mulch works because it traps air and helps moderate changes in soil temperature.

Step 8: Give Extra Attention to Newly Planted Perennials

Perennials planted this year deserve a little extra attention.

An established perennial has had time to develop a larger root system. A plant installed late in the season may have had only a few weeks to establish itself before temperatures dropped.

Make sure newly planted perennials are well watered going into freeze-up.

After the soil begins freezing, a layer of winter mulch can also help moderate soil temperature and reduce frost heaving.

This does not mean you need to build a huge mound over each plant.

A moderate, loose layer is usually more useful than burying the plant under a heavy pile of mulch.

Step 9: Protect Marginally Hardy Plants

When choosing perennials for Saskatchewan gardens, hardiness matters.

Zone 3 plants are generally better equipped to handle our winter temperatures than plants rated only for warmer growing zones.

If you are experimenting with a perennial that is marginally hardy in your area, its location in your landscape can make a significant difference.

A plant beside a sheltered foundation may experience very different winter conditions than the same plant sitting in an exposed bed where the wind continually blows away the snow.

You can give marginal plants additional protection with mulch after the ground begins to freeze.

However, winter protection cannot make every tender perennial reliably hardy in Saskatchewan.

Sometimes experimenting works. Sometimes it doesn't.

That is part of gardening.

Step 10: Don't Fertilize for New Growth

By fall, your goal has changed.

In spring, we want plants growing.

In late summer and fall, hardy perennials need to prepare for dormancy.

Avoid applying fertilizers intended to stimulate a flush of soft new growth late in the season. New growth may not have enough time to mature before freezing temperatures arrive.

Your plants do not need to look lush in October.

They need to be ready for January.

Prairie Tip: Snow Is Your Friend

Gardeners sometimes think of snow as something their plants have to survive.

In reality, reliable snow cover can be extremely beneficial.

Snow traps air and creates insulation between the soil and extremely cold winter temperatures.

This is one reason wind exposure matters so much in Saskatchewan.

An exposed garden where snow continually blows away can experience harsher conditions at soil level than a sheltered bed where snow accumulates naturally.

Leaving sturdy perennial stems and ornamental grasses standing can help catch drifting snow.

If you have a particularly exposed perennial bed, think about winter wind when planning future plantings. Shrubs, fencing and other garden structures can sometimes create a more protected microclimate.

A microclimate is simply a small area where growing conditions are slightly different from the surrounding area.

What About Fallen Leaves? Do we remove?

You do not necessarily need to remove every leaf from your perennial beds.

Leaves are natural organic matter.

A light layer can help protect soil and eventually break down.

The problem is a thick, wet mat.

Large amounts of whole leaves can pack together, hold excessive moisture and restrict airflow around low-growing plants.

If leaves accumulate heavily, remove some or shred them before using them as mulch.

Again, moderation is the goal.

Your perennial bed does not need to look perfectly clean before winter.

Common Fall Perennial Care Mistakes

Cutting Everything Down Immediately After the First Frost

One cold night does not mean the entire garden needs to disappear.

Allow plants to naturally enter dormancy and leave useful stems and seed heads standing where appropriate.

Mulching Too Early

Winter mulch works best when applied after the soil becomes cold or begins freezing.

Forgetting to Water

Cool weather can hide how dry the soil actually is. Check the root zone, particularly around new plantings.

Overwatering Clay Soil

Winter preparation does not mean saturating already wet soil.

Fertilizing Too Late

Avoid encouraging tender new growth as winter approaches.

Piling Mulch Against Crowns

More mulch is not automatically more protection. Thick, wet material directly against the crown can create problems.

Expecting Every Perennial to Survive

Hardiness zones matter.

Even with excellent winter preparation, plants that are not sufficiently hardy may not survive a Zone 3 winter, particularly in exposed locations.

Your Saskatchewan Fall Perennial Checklist

Before winter arrives:

• Remove diseased plant material.
• Pull weeds, especially those going to seed.
• Leave healthy stems and seed heads where they provide winter value.
• Cut back collapsed or problematic foliage.
• Check soil moisture.
• Deeply water new plants if conditions are dry.
• Add a light layer of compost if needed.
• Avoid late-season growth-promoting fertilizer.
• Wait until the soil is cold before adding winter protection.
• Mulch newly planted or marginally hardy perennials where appropriate.
• Avoid burying plant crowns under wet, heavy material.
• Let sturdy plants help catch insulating snow.

Then you can leave the garden alone for winter.

Frequently Asked Questions

When should I cut back perennials in Saskatchewan?

There is no single date. Wait until plants have naturally declined or been killed back by repeated frost. Many healthy, sturdy perennials can remain standing until spring.

Should I cut all my perennials down in fall?

No. Leaving sturdy stems, grasses and seed heads can provide winter interest, wildlife habitat and help trap snow.

Remove diseased material and foliage that becomes wet, rotten or problematic.

Should I mulch all my perennials before winter?

Not necessarily.

Established, reliably hardy Zone 3 perennials may not require additional winter mulch. Newly planted, shallow-rooted or marginally hardy plants are more likely to benefit.

When should I apply winter mulch?

Wait until the soil is cold and beginning to freeze rather than applying a heavy winter layer immediately after the first fall frost.

Should I water perennials after a frost?

Yes, if the soil is dry and not frozen.

A frost does not instantly freeze the root zone. Newly planted perennials in particular should not enter winter severely dehydrated.

Can I leave leaves in my perennial beds?

Yes, in moderation.

A light layer of leaves can provide organic matter and some protection. Thick layers of wet, matted leaves should be thinned or shredded.

Should I fertilize my perennial garden in fall?

Avoid fertilizers that encourage vigorous new growth late in the season. Fall is the time for hardy perennials to transition into dormancy rather than produce tender new shoots.

What is the most important thing I can do for newly planted perennials?

Make sure they have adequate moisture before freeze-up and consider adding winter mulch after the soil begins to freeze.

A Little Less Cleanup Can Be Better for Your Garden

Preparing perennial beds for winter in Saskatchewan does not mean making every garden bed perfectly clean.

A slightly untidy garden can actually be a healthier winter garden.

Leave useful stems standing. Let seed heads feed the birds. Allow plants to catch snow. Remove disease problems, keep newly planted perennials hydrated and add winter protection where it is genuinely needed.

Most importantly, work with the natural dormancy process rather than rushing it.

Prairie winters are demanding, but properly selected Zone 3 perennials are remarkably well adapted to cold weather. Your job is mostly to help them enter winter in good condition and then let them do what hardy perennials are designed to do.

Need Help Getting Your Perennial Garden Ready?

If you are unsure whether a particular perennial should be cut back, mulched or left standing, send your questions to Riverdene Garden Centre.

We are always happy to help you figure out what makes sense for your plants and your particular growing conditions here in Southern Saskatchewan.

The goal is not a perfect fall garden.

It is a garden that comes back healthy next spring.

       Riverdene Garden Centre