Transforming Your Septic Field into a Vibrant Prairie Meadow: A Step-by-Step Landscaping Guide (Part One)
- lesannsa
- Jul 7
- 16 min read
Updated: 7 days ago
by Leslie Ann Sadownik, July 6, 2025
Dreaming of a Prairie Meadow
The Dream
Instagram is brimming with stunning images of prairie gardens. Explore Piet Oudulf's stylized meadow in the Lurie Garden, Tom Stuart-Smith's prairie meadow, and Kelly Norris's hillside meadow. These images are inspiring to gardeners, yet also intimidating. Tom Stuart-Smith invested "several thousands of pounds sterling" in his seed mix, eradicated the grass in his 1/2 acre area with herbicide, added a 10 cm layer of sand on top, outlined a design, sowed his seeds, and meticulously weeded during the first year. He describes this initial year as "a nightmare". Now, he has a thriving prairie meadow which he calls 'low maintenance'. It seems there are many obstacles to overcome before reaching a meadow's 'low maintenance' stage.
The Reality
Despite my best efforts, my attempts to establish a meadow from seed have failed. When I sowed onto "bare soil", only grasses and weeds emerged. Clearly illustrating that I did not effectively address the dormant seed bank.
I have also tried (and failed) to introduce wildflowers like
Nodding onion (Allium cernuum),
Camas (Camassia quamash), and
Sea Blush (Plectritis congesta) into a field on the property.
I sowed Yellow-rattle (Rhinanthus minor) seeds into the same field. Dan Pearson has written about the critical role that the semi-parasitic Yellow-rattle plays in reducing the vigor of grasses so that wildflowers have a chance to establish in grass fields. Yet, I tried two years in a row, but still have not observed any Yellow-rattle plants. The grass is as vigorous as ever, and the wildflowers have disappeared.
Still, the desire to create a meadow was strong, urging me on.
Using Plants Instead of Seeds
I opted for a different approach: using plants instead of seeds. There are several advantages to using plants as starting material. By using plants rather than a seed mix, I could anticipate blooms sooner . Most native perennials will flower the year they are transplanted, whereas some native plants might take up to three years to bloom when grown from seed. Another benefit of using plants is that you can control the "design" of your meadow more easily. Using plants also makes it easier to identify and manage weed seedlings.
Finding a Suitable Site
An unused grassy site is the perfect canvas for a prairie meadow. Living in a rural area, we have a grass-covered septic field. This oval field is situated near our house in the middle of our driveway. It seemed an ideal location, but can you plant on top of a septic field?
After hours of background research into this question, I feel confident that the answer is YES; however, there are some definite do’s and don’ts about prepping, planting, and managing a meadow that are specific to septic fields. I'll walk you through these do's and don'ts as I describe the process step by step.
But before we dive right in, let's take a look at how a septic system works.
Understanding the Septic System
A septic system is an underground setup that receives, treats, and disposes of wastewater from the house. It does this in three steps.
First, wastewater flows from the house through a main drainage pipe to an underground septic tank. This wastewater settles into three different layers in the tank; scum (i.e. oil and grease), sludge (solids), and liquid. The scum floats and the sludge sinks. Both are digested by bacteria in the tank.
The "treated" wastewater is then piped from the tank to a distribution box. From there it flows through pipes into the "drain field". These perforated pipes are laid in trenches that are filled with gravel.
The wastewater flows out of these pipes into the gravel trenches and drains into the soil underneath. The soil naturally filters and purifies the effluent, removing bacteria, viruses, and nutrients before it eventually returns to the groundwater.
This is the basic system; sometimes the wastewater needs to be pumped up to a drain field, and/or holding tank, as there is no suitable site for a gravity fed drain field near the house. Sometimes there is no suitable soil available to filter the wastewater and the water will need to be treated before it drains into a purpose build septic mound.
Why is it important to understand how a septic system works?
First, it is useful to know the location of the underground equipment (tank, distribution box, pipes) before you start preparing the site. Ensure the septic tank lid is easily accessible for maintenance. The septic tank may need to be pumped out on a regular basis, and if the system stops working, you will need access to this tank.
Next, the system relies on healthy soil bacteria in the drain field to treat the wastewater. Healthy soil needs to breathe. Thus, you cannot prepare the site by covering it with impenetrable material like plastic. Nor can you solarize the soil with plastic, as this will kill the healthy bacteria.
A drain field also needs to drain. Heavy equipment, vehicles, livestock, etc., should be kept off the field. The weight will compress the soil and could crush or damage the underground structures (tank, box, pipes).
Drainage pipes may be anywhere from 15 cm (6 inches) to 60 cm (2 feet) below the surface. For this reason, trees and shrubs should not be planted within 8 m (25 feet) of the field. Plants with deep woody roots will be attracted to the water, and the roots may eventually fill up the field and even block the drainage pipes.
Finally, you do not want to overload the field's draining capacity. Therefore, you should not be adding additional water (i.e., irrigation) to the field.
Planning Your Prairie Meadow
Step 1: Assess the Site
Characteristics of the site that need to be assessed include:
local climate & hardiness zone
aspect of the site and sun exposure
soil type and soil drainage
existing vegetation
Climate & Hardiness Zone
Prairie plants are hardy and thrive in Canadian Plant Hardiness Zones 2-6. Living on one of the Southern Gulf Islands in British Columbia, we are situated in the rain shadow of the mountains of Vancouver Island. The climate is Mediterranean-like. We are in Zone 9B (hardy to -6.7 – 1.1°C). The average temperature is around 6 degrees (Celsius) in the winter and rises to an average of 21 degrees in the summer. So the temperature is suitable. The islands also receive between 60 and 100 cm of rain per year – mostly during winter. Again, that should work as ideally, a prairie meadow should receive 50-100 cm of annual precipitation.
Aspect and Sun Exposure
Meadows do best when they receive at least 6 hours of full light. Our site is south facing and receives over 6 hours of direct sunlight per day.
Soil Type and Soil Drainage
Prairie plants are adaptable, and can thrive in sandy, loamy, or clay soils. In general, most septic fields will be located in sandy or loamy soil that drains well. Clay soils, on the other hand, are "heavy" soils that have high water holding capacity and drain poorly. Prairie plants do grow well on loamy soils with a pH range of 6.0 - 7.5. The soil on my site is sandy loam, which makes it ideal for a prairie meadow.
Existing Vegetation
A planting site should be free of invasive weeds, trees, and/or shrubs. Our field was covered with native grasses/turf, but patches of dock weed, Canadian thistle, and nettle needed to be removed prior to planting. There were also several large trees located at both ends of the field, so there was a possibility of tree roots reaching into the field.
Location and Type of Septic System
If possible, you want to locate the septic system as accurately as possible. It is helpful if you have a reference drawing of the location of the tank, box, and underground pipes. The blueprints for your property may include a diagram of the septic system.
If the septic field was professionally installed, the regional health authority may have records of the septic installation. If you do not have any records, then inspect your field. We were able to locate the opening for the septic tank, and the ground over the drain pipes was marked by lush plant growth.
Step 2: Choose the Right Plants
Putting together a list of suitable plants is exciting. The success or failure of the project will depend on selecting the "right plant for the right place" and then giving that plant the "right companions."
Drought-tolerant Plants
Since you won't be irrigating your septic field, it's best to select drought-tolerant plants. The right plants for a septic field have superficial roots that penetrate only 15 cm (6 inches) or less into the soil. If your pipes are very near to the surface, and you have less than 15 cm of topsoil, you may need to increase the depth with additional soil before planting.
The best plants are herbaceous plants (perennials and grasses) with fibrous root systems. Plants with deeper roots (e.g., tap roots), or woody roots (shrubs or trees) can grow into the drainage pipes, potentially cracking or clogging the septic system. You also don't want to choose plants that like wet conditions (i.e., bog plants), as their roots will also grow deep down seeking out water.
Mix Grasses with Forbs
Your list should include a mix of native grasses (60-65%) and forbs (35-40%) to achieve a balanced meadow look. Forbs are flowering perennials. You may even want to go as high as 80% grasses and 20% forbs, or as low as 20% grasses and 80% forbs. It depends on how 'natural' you want your meadow to look. You can also add in annual wildflowers to help fill in the gaps in your meadow.
So begin your plant list with grasses. Choose bunching grasses over turf grasses. Turf grasses aggressively spread by rhizomes and can quickly take over your meadow. Grasses are categorized as "cool" or “warm” season grasses. Try to include a mix of cool and warm season grasses. Cool season grasses grow early in the season, thus providing a flush of green to the meadow when everything else is brown and dormant. They flower in early summer and then go dormant.
Warm season grasses are basically dormant in spring, will green up in summer, and flower in late summer. Warm grasses often turn lovely colours in fall.
Their late blooms and color will enhance the fall/winter garden; however, warm season grasses can be very slow to start growing in the season. It is best to test them first in your climate before you depend on them in a design.
Since grasses may make up half of your planting, they will serve as the "mortar" that will hold your design together. In small areas, you may only want to use two different grasses. In larger areas, three to four different grasses can be used. I selected a variety of grasses as I wanted to test which grasses performed the best on my site.
My list included cool-season grasses such as
Festuca roemeri
Koeleria macrantha
Deschampsia cespitosa
As well as warm-season grasses such as
Bouteloua curtipendula and
Muhlenbergia capillaris
Determine the Number of Species
You will have to decide on the total number of species you want to include in your meadow—and the relative proportion of each species. The higher the number of species, the greater the biodiversity. In the wild, a healthy natural prairie meadow may have 20-30 plant species per square meter.
However, when you limit the number of species and repeat certain species throughout the planting, you will create a better sense of rhythm and abundance in the meadow. Typically, a small designed meadow may contain 7-15 flowering species and a larger one 15-25 flowering species.
Specific Plant Choices
In regard to choosing the right drought-tolerant flowering perennials, some factors to consider include:
method of spread
plant size, shape and height
blooming time
flower form and colour
Method of Spread
Avoid thuggish plants that spread aggressively by rhizomes or seeds. For example, Heliopsis helianthoides (Oxeye Sunflower) is known to spread aggressively by seed, and Heliopsis x laetiflorus will spread aggressively by rhizomes. If you add these plants, be prepared to end up with a meadow full of sunflowers.
Plant Habits and Forms
The goal of your design is to knit plants closely together to crowd out weeds. You can plant more densely if you fit plants together by combining plants with different growing habits and different forms at maturity. Choose plants that fill out different layers in the planting. For example, plant a ground cover with leaves at the base, next to an upright plant with leaves along the stems, next to a clumping grass with arching leaves.
Blooms, Flower Form and Flower Colour
You want to create a succession of blooms by picking plants that have different bloom times. This will enhance the beauty of your meadow and help to support pollinators throughout the season. Different pollinators are attracted to different flower forms and colours. So, in order to attract a range of pollinators, choose different flower forms (e.g., daisy-like, spikes, tubular, umbrella-like) and different flower colours (e.g., hummingbirds are attracted to red, yellow, and purple).
Ecological Benefit
Finally, and perhaps most importantly, make a point of adding plants that best support wildlife. Insect populations are declining globally. This will have a catastrophic effect on all ecosystems. Plants that support wildlife by providing shelter, nesting sites, and nutrition will benefit your local ecosystem. A meadow that is alive with wildlife is a captivating sight.
Native Plants or Cultivars?
So should you choose only native plant species? Native plants have adapted to your local conditions, and local insect populations rely upon them. So a large proportion of your meadow should incorporate native grasses and flowers.
However, there may be cultivars of native plants (e.g., Agastache 'Blue Fortune') that provide similar wildlife benefits, but have better horticultural performance (disease resistance, longer bloom time, drought tolerance).
But beware, many cultivars of species plants may look pretty but do not support pollinators. For example, single-flowered Echinacea purpurea will support bees, butterflies, moths, and birds. But newer double-flowered or pom-pom Echinacea cultivars (e.g., Double Scoop Bubble Gum Echinacea hybrid) are poor substitutes—the double flower physically blocks the insects from reaching the flower's pollen and nectar.
As well, many new cultivars are often sterile and do not produce seed—so no food for birds. You can find the results of plant trials that compare different species and cultivars on the Mt. Cuba website.
Tip - The Gardener's Guide to Prairie Plants (see references) provides handy tables that list a variety of plant characteristics such as ideal soil conditions, bloom time, plant spacing, root type, plant life expectancy, plant aggressiveness, and method of spread.
Sourcing Your Plants
The planting density for a designed perennial meadow is 5-10 plants per square meter. Plants in meadows grow closer together than in gardens. For example, the recommended plant spacing for Echinacea purpurea in prairie gardens is 30 cm apart, whereas in flower beds the spacing is 60-90 cm.
For a meadow, a useful rule of thumb is to plant every 30 cm. Yes, some large plants will easily fill a square meter when mature, but if you choose the right companion plants, these plants can overlap successfully together. My area is approximately 200 square meters. So even on the lower end of plant density, this would translate into 1,000 plants.
My strategies to achieve (or come close to) this number was to
start native plants from seed months ahead of planting time
divide and transplant suitable plants already in my garden
buy plants on sale in fall and divide them into multiple plants
buy plant plugs in spring
Finding Plugs or Plants
Plugs are baby perennial plants. Some nurseries will offer plug trays which typically hold 50 plants. For example, Satin Flower offers a variety of grass and flowers in plug trays - a tray of 50 Deschampsia cespitosa is $150 or $3 per plug. This is much cheaper than 1-gallon pots that range from $5-8 at wholesale nurseries. A packet of seeds is even cheaper ($6) and often contains hundreds of seeds. So if you plan ahead, you could start your own plugs. I ordered seeds from a variety of sources the fall before planting.
Seed Mixes
As an aside, seed mixes can be much more affordable than plugs or plants. However, the mixes can vary greatly in cost. For example, Prairie Moon has a "Classic Tallgrass Prairie Mix" that will cover 1/8 of an acre (500 square meters) for $114 (US). Custom seed mixes will cost much more. Jelitto Seeds offers a J. Hitchmough Design Mix A: Steppe Prairie, which is €5.20 per gram, and the recommended seed rate is 1 gram per square meter.
Starting From Seed
Back to starting your own plants, many native plant seeds require a period of cold stratification (a process where seeds are exposed to cold, moist conditions to break dormancy and encourage germination). So it is ideal to sow these seeds in fall and let them overwinter in an unheated greenhouse. The plants will germinate in spring and can be potted up in plug trays (8 cm or greater depth). Seeds that do not need a period of cold for germination can be started in spring. If all goes well, plants will be a suitable size with a well-developed root system by early summer to fall.
Step 3: Clear and Prepare the Ground
In order to establish a meadow, you need to (1) remove all existing weeds and (2) manage the existing seed bank in the soil. Weed seeds will outcompete most perennial wildflower seedlings. So, if you decide to establish a meadow through sowing, site preparation will be critical for long-term success. Typically, the options for preparing a new site include:
mulching
solarization
tilling
removing the sod
burning
herbicides
Smothering
If you use smothering as a method to eliminate weeds, you will leave the smothering material (e.g., cardboard, plastic) in place for an extended period of time (e.g., 2-6 months) then remove it for an interval (2-4 weeks). The dormant seeds will then germinate when exposed to light. Then you will cover the soil again with the same material for another 2-6 months. On again-off again smothering cycle to exhaust the endogenous seed bank. However, covering a drain field can interfere with the function of the field - water needs to evaporate. So smothering is NOT an option for septic fields.
Solarization
As previously mentioned, solarization will destroy healthy soil bacteria, so again NOT an option for a septic field.
Manual Removal
Manual removal of existing vegetation and weeds is another option. Removing sod has challenges. If the sod/soil layer is very superficial above the tanks and pipes, removing the sod may expose these structures. You cannot use any heavy equipment to strip off the sod. If the site is small, you can use manual tools (sod cutter and square garden spade), but if the site is large, this could be onerous.
Ultimately, new soil/sand may need to be added to cover any exposed structures. The depth of your septic equipment will determine if superficial tilling is a feasible method. As tilling brings new weed seeds to the surface, tilling would need to be repeated (e.g., every six weeks) in order to exhaust the seed bank. So what does that leave?
Septic Safe Options
Methods that are suitable for septic fields include controlled burning and the application of herbicides. Given the surrounding trees, burning was not an option. All gardening is an act of intervention that has negative and positive effects on the environment. I felt converting this field to a pollinator meadow ultimately was going to improve the aesthetic beauty and ecological services provided by the converted land.
So, after reading arguments for and against using a herbicide for transforming a lawn into a meadow, and given the limitations imposed by using a septic field, I decided to proceed with the application of a herbicide only for the purpose of preparing the site. It would result in less soil disturbance, fewer weeds, and sooner yield ecological benefits.
The "Direct" Method
Some authors, like Owen Wormser, have reported success sowing and/or planting into existing turf grass with minimal site preparation. Seed can be freely broadcast into a field, or sown directly into the soil (sowing into pitchforked holes). Plugs can be planted directly into the existing turf. Fast-growing and aggressive prairie species are probably the best plants to try to introduce with this method. Also, you will not want to use this method in sites with invasive weeds (e.g., blackberry).
Enhancing Soil Quality
Most native plants are adapted to grow in lean, nutrient-free soil. Plants that are stressed for nutrients and water will develop stronger root systems. Adding compost and/or fertilizer to enhance the nutrition of the soil will likely result in weed growth and excessive vegetative growth. I chose not to enhance the fertility of the existing soil.
Summary
In Part One, we covered the initial steps to convert a septic field into a flourishing meadow. These steps are: (1) site assessment; (2) selecting appropriate plants; (3) clearing and preparing the ground. We're on a promising path! Move on to Part Two to learn about: (4) designing your meadow, (5) planting, (6) watering and maintaining your meadow. I'll also share an update on what's 'working' and 'not working' in my planted meadow!
Useful Reference Books
Diblik, R. (2014). The Know Maintenance Perennial Garden. Timber Press.
King, M. Perennial Meadows (Ebook series) accessed July 3, 2025. https://www.perennialmeadows.com/prairie-perennial-meadows-ebook/
Norris, K. D. (2021). New Naturalism: Designing and Planting a Resilient, Ecologically Vibrant Home Garden. Cool Springs Press.
Norris, K. D. (2025). Your Natural Garden: A Practical Guide to Caring for an Ecologically Vibrant Home Garden. Cool Springs Press.
Oudolf, P., & Kingsbury, N. (2013). Planting: A New Perspective. Timber Press.
Vogt, B. (2023). Prairie Up: An Introduction to Natural Garden Design. University of Illinois Press.
Wormser, O., & Thompson, K. (2020). Lawns into Meadows: Growing a Regenerative Landscape. Stone Pier Press.
Helpful Blogs
"How to Plant a Meadow" Northwest Meadowscapes
"How to Prep Your Site for a Native Seed Mix" Prairie Moon Nursery
"The Deep Middle" excellent blogs by Benjamin Vogt that cover many of the topics discussed above in greater detail. See also his book.
Interesting Websites
Plant and Seed Resources
Akene Seeds: native plant seed supplier from Quebec. https://akene.ca/en
Novus Plants Wholesale Nursery: a wholesale-only nursery serving Vancouver Island @novusplantswholesale
Northwest Meadowscapes: a native seed farm located on Whidbey Island, USA, specializing in the cultivation and sale of native grass and wildflower seeds for the Pacific Northwest region. Seeds and meadowscaping consultation. https://northwestmeadowscapes.com
Prairie Moon Nursery: a nursery in Midwest, USA, with a very large catalog of native seeds. Will ship to Canada. https://www.prairiemoon.com/meet-prairie-moon.html
Phoenix Perennial: a retail and mail-order nursery in Richmond, BC, with a large mail-order catalog featuring many West Coast native plants. https://www.phoenixperennials.com
Satinflower Nurseries: an ecological native plant nursery on Vancouver Island. Seeds, plugs, and meadowscaping consultation. https://satinflower.ca
Stellata Plants: a small nursery on Vancouver Island specializing in rare to find drought tolerant plants. Pick up only. https://stellataplants.com
West Coast Seeds: located in BC, offers a selection of native flower seeds. Westcoastseeds.com
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