Planting a Swale on the Alberta Prairie

Image showing blue flax flowers in a drainage swale

According to, a swale is “a shallow, trough-like depression that carries water mainly during rainstorms or snow melts.”

Another accurate definition by “Bioswales are vegetated, shallow, landscaped depressions designed to capture, treat, and infiltrate stormwater runoff as it moves downstream.”

Why to plant a swale

The purpose of a swale is to allow water to infiltrate the soil rather than running off or pooling in undesirable areas. It may be a gentle slope to ensure water doesn’t pool at a home’s foundation (such is the case with our swale).

A swale slows runoff and can help manage storm water. Water is filtered by plants and soil as it seeps into the earth and recharges the groundwater.

A swale can add beauty to landscapes and can be highly beneficial to native wildlife (depending on your choice of native grasses and forbs).

When to plant

You have a choice! You can plant in the fall or the spring. It depends somewhat on the species you choose to plant as well as if you choose plugs or seeds.

Warm season grasses generally prefer to be seeded in spring, while cool season grasses may prefer fall or winter seeding.

Some forb seeds need a period of cold stratification in order to grow, and therefore would benefit from a fall or winter sowing. It’s really important to check this for each type of flower seed you want to sow. However, if you haven’t gotten around to seeding in the fall when you should have, it is possible to imitate a natural cold stratification by using this refrigerator method.

Prepare the site

Assuming your swale is already formed and ready to go, your first step is to ensure the soil is as weed free as possible. (If you don’t have a swale yet but think it would benefit your landscape, check out this video for a detailed guide).

If possible, prepare the site for a full year before planting. This way you can really conquer the weeds, which will reduce your workload immensely following seeding (or planting plugs).

Ideally, choke the weeds using a large sheet of dark plastic such as silage plastic, or a tarp. Alternatively, overlapping sheets of cardboard could work well. In a very windy area like ours, you will need to make sure your plastic or cardboard is weighed down with heavy objects (I use large rocks).

To also eliminate late season weeds, you may wish to uncover the area later in the season to allow any of those weeds to germinate, and then cover again. (Depending on moisture levels, you may need to water the area when it is uncovered so that the seeds will have what they need to germinate.)

Other methods include using herbicides (which I do not recommend because of the many downsides of herbicide application) and solarization.

Solarization uses plastic to trap heat and moisture in order to kill weeds and seeds as well as insects, bacteria, fungi, etc. I am not convinced that it’s wise to use this method for weed control for our purposes either, since we know that soil organisms are essential to good plant growth.

Some people choose to till a few times to try get rid of weeds, but again this may not be the best option. First, you’re severely damaging the soil structure, and secondly, each time you till there is a high likelihood of additional weed seeds being brought to the surface.

If time is not a concern, it could be a great idea to plant a cover crop or two in preparation. These crops will build soil health and structure (as well as adding organic matter) while choking out weeds.

Order seeds or plugs

Honestly, at first I found it very difficult to get my hands on native grass and flower seeds! I emailed and called around to multiple seed companies, but most did not seem interested (small fish, maybe?).

Gold Medal Seeds

Then I contacted Gold Medal Seeds in Brooks, Alberta, who claim they are the largest suppliers of reclamation grasses in Southern Alberta. Eric made helpful recommendations regarding which grass seeds were best for my situation.

We settled on Purple Prairie Clover, Junegrass, Blue Grama Grass, and Blue Flax for the outside edges of the swale, which is generally a dry area. Then for the bottom of the swale which is often more moist, I went with Ticklegrass, Tufted Hairgrass, and Purple Prairie Clover (which may or may not work there; online info is conflicting. I’ll keep you posted!)

Update January 2023: Purple Prairie Clover has done very well in the bottom of the swale, maybe better than the sides. Apparently the additional moisture was beneficial!

Update January 2023: Another interesting development…the blue flax did really well the first year, but was hardly noticeable the second summer. I’m not sure why. We’ll see how it looks this coming summer!

Blazing Star Wildflower Seed Company

I had to source the remainder of the wildflower seeds elsewhere, as Gold Medal Seeds doesn’t carry them. I ordered some online from Blazing Star Wildflower Seed Company– Smooth Aster, Slender Beardtongue, Prairie Coneflower, Gaillardia, Dotted Blazingstar, and Black-eyed Susan. It was $90 even for 5 packets of each. They are very tiny packets, I realized after I received them!  

Wild About Flowers

After I had placed that order, I finally heard back from Wild About Flowers, whom I had emailed earlier with questions. They apparently were swamped during the spring and having a hard time keeping up with emails (it seems everyone is growing wildflower gardens during this pandemic?).

Arden was super helpful and gave feedback regarding each kind of seed I was considering. After a bit of back and forth, I did settle on a few different varieties: Wild Chive, Nuttalls Larkspur, Fireweed, Wild Strawberry, Wild Mint.

I did not love the process/website. If you’re anything like me, you like to browse, add items to the the cart, sometimes take them out and add different ones. Then you leave them until the next day to consider or research, or you just get distracted by your children and forget to place the order.

This cart didn’t save anything past about an hour or so! So that was unsettling and discouraging and I had to redo everything more than once before I was ready to place my order.

Then, my order was basically emailed to them to check if everything was in stock and only then would they email an invoice which had to be paid by a certain date. Following payment, they would ship out your order. So all in all, not a totally seamless online purchase.

However, during the summer I made a trip with my sister and visited Wild About Flowers in person. What a beautiful, organized sales area!

And each of the tiny plugs I purchased there (from $5-7.50 each) grew and flourished well this summer, and some of them even provided many seeds this first year! I would highly, highly recommend going the route of plugs if at all possible.

ALCLA Native Plants

Four trays of native plant and grass plugs from ALCLA Native Seeds in Calgary, Alberta

We also visited ALCLA Native Plants. While their physical sales area was definitely not as organized as Wild About Flowers, it was enjoyable to browse. (I’ve meanwhile ordered plugs from here for next year and will keep you updated about that!)

I purchased some plugs from here also, which grew equally as well as my Wild About Flowers plugs.

For online purchases, they require an emailed list of species to purchase, after which they will send a SquareSpace link where you can conveniently pay for your order.

Plant seeds or plugs

As I stated earlier, I would absolutely recommend planting plugs if your budget permits (and the installation will of course require more effort). Since I have not yet planted a large area with plugs, I can’t speak more to that, but I hope to have a detailed post about it in Spring 2022!

But it’s completely reasonable to go the seed route if that’s what your budget and time allow! Especially grass seed is fairly easy to get established from seed, and then you could plant islands of forb plugs.

If you spread your seed mixture by hand, use about half of your seed mixture first and go over the area. That way you won’t be overzealous about the seeding and run out, like I did 🙂

Check out Prairie Moon’s excellent guide to planting native seed. I came across this resource while writing this post and wish I’d seen it sooner.

Water, water, water

The end goal is to have a lush area that doesn’t need supplemental watering, except in the event of an extended drought. However, to get to that point…seeds do need water to germinate and grow! As do freshly planted plugs.

Unless you live in an area that gets regular precipitation, you WILL NEED TO WATER your newly planted area for the first season of growth. Even for those plants that will be drought tolerant once established!

Mow if necessary

If you’re noticing a lot of weeds during the first season of growth, you will want to mow the area with the mower set as high as possible. Definitely do this before weeds go to seed.

This will not harm the new native seedlings, and may in fact encourage stronger root growth. You may need to mow a few times in the first season of growth, and possibly in the second season as well.

Enjoy the fruits of your labor

Not only will you be able to enjoy the beauty of native vegetation and flowers, but the hum and activity of bees, butterflies, birds and other creatures will keep you smiling.

Happy Gardening!