How It's Done
CHERYL BRADLEY LEADS BY EXAMPLE
A dream to create a prairie urban garden has been with me for many years. Since the early 1990s my husband and I have lived in a post-war vintage house in southern Lethbridge with a large front and back yard occupied mostly by lawn. Lawn is not something we use or enjoy. Our lawn uses us as we must regularly mow the grass and water it. We resent spending valuable time and resources nurturing Kentucky bluegrass and creeping red fescue, two exotic invasive species which we often rail against in our work as prairie biologists. While I dug dandelions and creeping bellflower from the lawn, my mind would often dwell on visions of living more in harmony with the native prairie ecosystem which I enjoy.
1. Beginning with a Vision
My vision for our front yard is not of semi-arid grassland, but rather a prairie valley. The yard is shaded from May to September by two large streetside elms growing on the property of neighbours to the north and south. Elms are native to prairie valleys in Manitoba and Saskatchewan and well adapted to southern Alberta’s environments where groundwater is close to the surface. These trees will be with us for many years to come provided our city is kept free of Dutch elm disease. The sun-screening canopy, shelter from drying winds and elevated water table from urban development means our front yard is an environment more suited to native shrubs and perennial forbs than short grasses and annuals common in dry upland prairie.
A large weeping birch planted in the centre of the front lawn was removed on the advice of an arborist as it was damaged from a poor pruning job and under stress. Not well adapted to the prairie environment, its roots were constantly creeping into cracks in our tile septic drain questing for water. Having recently replaced the driveway and steps to our front door, re-insulated and re-sided our two-storey house, and replaced our leaky septic tile with plastic pipe, we realized the time had come to make our prairie urban garden a reality.
2. Creating a Design
After perusing several books on gardening, I realize that the essential first step is to translate my vision into a design. How hard can it be to map a plan for an area 170 m2 (11 metres x 15.5. metres)? Some homeowners with artistic sense, an understanding of plant structure, moisture and space requirements and knowledge of the options available for mulches and hard surfaces may find this easily doable. However, several pieces of graph paper with amateurish scribbles are tossed in the recycling bin before I come to the conclusion that I need the help of a professional.
I seek recommendations from friends and acquaintances and make a few cold calls to landscape contractors and designers listed in the yellow pages. I am surprised to discover that of several dozen companies listed only a handful employ individuals trained in design. A few interviews later, my husband and I choose to contract Earthlings Landscape Design and Construction.
Kirsten Hironaka, designer and principal in Earthlings, is eager to create a design consistent with our criteria of applying the seven principles of xeriscaping (see xeriscaping principles), using native plant species where possible, and having a yard that is low maintenance. Visiting a few of Kirsten’s previous landscaping projects affirms for me that we also shared a similar sense of beauty. There is no sense investing in a landscape that my husband and I will not appreciate and enjoy.
Kirsten and I have met a few times over the past year to refine the design. We agree that there will be a narrow flagstone pathway running diagonally through the garden with a small patio near the house. This will allow us to enjoy our garden and to watch the evening light fading to the west. It will also provide opportunities to visit more with our neighbours.
We will use shredded wood mulch over the bare soil to reduce evaporation and weeds. Over time, as the plants mature and spread, much of the wood mulch will decompose and provide structure and nutrients to the soil. Gravel is more difficult to maintain and keep free of debris and weeds. As well, it can absorb a lot of heat on hot days, increasing drought stress for plants.
We decide not to install a buried irrigation system. Instead we will choose plants that are adapted to our semi-arid climate. We will water only when needed using a hose attached to the outdoor tap or the rain barrel.
Kirsten’s design is based on consideration of form, structure, texture and colour of the plants throughout all seasons. There will be a small drought-tolerant turf area near the street backed with perennial beds and low shrubs which in turn are backed with progressively taller shrubs until the eye comes to rest on an existing columnar cedar and a new small tree to be planted near the house. There will be a mix of deciduous and evergreen shrubs; the evergreens will maintain their form and colour through the winter. Perennial beds will produce dense patches of colourful blossoms, primarily yellow, burgundy and pink although a few white ones are okay too. Some of the shrubs will have pink flowers too, or purple bark or yellow leaves. A few bunch grasses will be added for visual interest. Most species will be planted in groups of three, apparently a principle of design.
Kirsten also is mindful of the landscaping of our neighbours and seeks to create a design which has an overall pleasing visual effect. Our neighbours to the north have a yard filled with trees, shrubs and perennial beds. The garden portion of our design will blend seamlessly with theirs. The turf portion of our design will visually complement the lawn of our neighbours to the south.
Although we now have a design on paper, Kirsten makes it clear to me that it is her prerogative as the designer to tweak the plan during installation... it is part of the creative experience.
3. Choosing Plant Species
As a botanist, I find choosing the plant species for the garden one of the most enjoyable aspects of this project. My husband is less interested so these ‘small’ decisions are left to me.
I hope to use native species, but realize this part of my vision may not be realized given the design’s specifications regarding form, structure, texture and colour. As well, native plant material may be difficult to obtain. Most nurseries stock few if any native plants and digging them up in the wild is against the law.
I consult my native plant books and prepare a list of native trees and shrubs that might meet design requirements for height and form (mounded, round, columnar, arching branches, spreading branches). Kirsten brings her knowledge of non-native wood ornamentals to the conversation.
In the end we agree on Schubert chokecherry for the small tree to be planted at the back of the garden; it is a cultivar of the native chokecherry found in Lethbridge coulees, grows to five metres tall and has foliage that turns purple-red in late summer.
Surprisingly, several deciduous native shrubs also will meet design requirements. Red-osier dogwood, thorny buffaloberry and snowberry, all native to the Lethbridge river valley, will have a place in the garden. Waterton mockorange, a native of the southwest corner of Alberta, will fit; we’ll plant two more beside the one that is already there. Kirsten and I also agree on the summer-wine ninebark and spiraea. They are cultivars of species native to eastern Canada and have cousins native to montane meadows and open woods in southwestern Alberta. The summer-wine ninebark has burgundy leaves and pale pink flowers. The goldflame spiraea, as its name suggests, has yellow to reddish leaves.
The three coniferous shrubs that meet design requirements – mugo pine and dwarf junipers - are cultivars of species native to Europe and Asia. The ground juniper and creeping juniper native to southern Alberta form large, spreading mats rather than being roundish or fountain-like in form. In addition the native junipers lack the blue-green foliage of the blue tam and mint julep junipers.
I next prepare a list of native prairie forbs that have yellow, burgundy or pink flowers and that may be commercially available as plants or seeds according to the Alberta Native Plant Council source list. The design does not allow for blue or orange blossoms, but white is okay. The resulting list contains about seventy perennial species. I am hopeful that we will find the dozen or so needed to accomplish the design. However, as Kirsten and I work our way through the list, the large majority are scratched off because their foliage and blossoms are not showy enough, the blossoms fade too quickly, the plants are subject to spreading or disease, or their survivability in an urban garden is questionable. The characteristics that horticulturalists select for become abundantly clear.
In addition, Kirsten is somewhat nervous about using species that she is unfamiliar with and that may be hard to find in local nurseries. It is also clear that little horticultural work has been done with native prairie forbs. I hope this will change over the next few years.
Two bunch (tufted) grasses which will provide subtle accents in the garden finish off the plant list. Rocky Mountain fescue is native to Alberta. Feather reed grass is a drought tolerant ornamental. We will decide on the list of species for our turf grass mix later.
Of our final list of twenty plant species to be planted in the garden, half are native to the Canadian prairies (if not specifically to southern Alberta) and half are native to semi-arid environments elsewhere in North America, Europe or Asia.
4. Deconstructing the Old Landscape
A proposed late May starting date for beginning work on the re-landscaping is delayed by several weeks due to heavy late spring and early summer rainfall. On July 1, Lethbridge experiences one of its heaviest downpours ever, flooding roads and basements. Periodic heavy showers continue into mid July. It’s foolish to work in the mud. Kirsten and I are in regular touch and I realize the delays are much more frustrating to her than to me. She is juggling the needs of several clients.
The second week of July, men working for the City water utilities, gas company and telephone company come by to place different colored flags on the path of buried lines and to leave records of their findings in our mailbox. This is an indication that work will begin soon.
Finally on July 16, after a few dry days, Kirsten’s husband Clayton and a crew of young men arrive with a small, maneuverable skid-steer Bobcat (S185) and remove our lawn. The stripper blade cuts into the top soil to a depth of about 15 to 20 cm, sufficient to remove most if not all of the grass roots. Clayton is careful to remove enough of the subsoil so that the flagstone path, which is to be put on a gravel and sand base, will be at grade with the sidewalk at one end and our driveway, upslope about half a metre, at the other end. He also is mindful to grade the surface so water will not pool next to the foundation of our house.
The turf and dirt are loaded into a dump truck using the Bobcat with a bucket attached. This is hauled to a large composting site that Earthlings maintains. The large straggling juniper in front of the cedar which remains is cut down and hauled away. A two-metre-tall mountain ash is more carefully removed and transplanted to Earthlings’ acreage. A peony near the house is left in place for transplanting in the fall or spring.
Within just a few hours we are left looking out our front window at bare, brown dirt contemplating how quickly this destructive phase of our landscaping project occurred. We are glad it was not us who had to do it.
5. Laying the Flagstone Path and Patio
It rains again, which is unusual for mid-July. I accompany Kirsten to Burnco’s storage yard in West Lethbridge to choose flagstone for the path and patio. There are over a dozen types, each named according to the place of origin. I feel a tinge of guilt realizing that mountains are being torn down to create paths for people in cities. Our footprint on this earth reaches into unexpected places.
We choose two pallets of Kendall flagstone. The colour is gray with slight reddish hues and will blend with the driveway and sidewalk and complement the grey-green of our house siding. The flagstone pieces are close to two inches thick and relatively large in area which will make it durable and easier for Clayton to install. It is also relatively inexpensive.
Another week passes before the ground dries out enough to lay the flagstone path. On July 23, Clayton and his crew of young men again arrive, with a smaller Bobcat. A small load of gravel is delivered as are a few cubic metres of sand. These will form the base for the flagstone, allowing a level surface and good drainage.
With the landscape design in one hand and a can of white spray paint in the other, Clayton marks the outline of the flagstone path and patio in the dirt. I am asked and confirm that it is consistent with our plan. Under his watchful eye, Clayton’s crew levels the patio site using square shovels. Using the loader, they haul gravel to fill the outline to a depth of about 10 cm, and smooth it out with rakes. The gravel layer is topped with 5 to 10 cm of sand. Edges are smoothed and tapered. This is a solid base for the flagstone. Our design is starting to take shape.
Watching the laying of the flagstone is like watching a large jigsaw puzzle being assembled. I have a bird’s-eye view from my upstairs office window. Clayton starts against the driveway and sidewalk with large, straight-edged pieces and also lays larger stones having rounded edges along the outer edge of the patio. The crew works to match the edges of these first-laid stones as closely as possible with other stones in the pallet. Flagstones are strewn across the yard and regularly reorganized as they are tried and rejected.
Each section is assessed by Clayton who ensures the edges match closely enough to avoid large spaces and the rock pattern “flows” appropriately. At those places where a suitable match cannot be found, Clayton “cheats” by scoring the surface of a rock that almost fits to match overlapping rocks and using a special saw to cut along the line. Once the pattern is given the nod of approval the flagstones are leveled by adding or removing sand. Cracks between stones are filled with a polymeric stone dust which is hard when dry and soft when wet; it prevents ants and weeds from establishing as well as erosion. I take pleasure in watching the creation of this flagstone puzzle and admire its form and pattern when completed.
6. Preparing the Topsoil
On July 26, Vic Bzdell brings in topsoil by dump truck. This is dark brown topsoil, salvaged from development sites, that has been mixed with aged manure and straw to provide nutrients and structure. The soil is tested periodically for nutrient levels (nitrogen, phosophorous, potassium), electrical conductivity, pH and organic matter. It has been composted to kill most, if not all, weed seeds.
Clayton uses his bobcat to spread the topsoil to a depth of 10-15 cm.
Plastic board of earthen hue, about 1 cm wide and 15 cm deep, is sunk in the soil to mark the border between the area that will be garden and that which will be turf. It is meant to prevent the roots of grasses from invading the garden. The plastic is easily bent to make contours more pleasing to the eye than straight edges.
7. Planting the Garden and Mulching
Immediately after the topsoil is spread, the planting begins. Most of the plants for the garden have been grown in a southern Alberta nursery. The exception is evergreen shrubs which have been grown in a nursery in southern British Columbia. The plants have been stored in pots at Earthlings’ yard since spring. All are assessed as healthy and hardy for our semi-arid continental prairie climate.
Kirsten directs the planting, using our draft design and plant list but also using her creative discretion to modify various elements. For example, an elder takes the place of two ninebark and the three goldflame spirea are planted on the streetside of the the patio near the driveway rather than close to the house. An alpine currant is planted in a space originally designated as part of a perennial bed to provide a screen between the patio and the street. This means there is not room for wild bergamont or dotted blazing star, somewhat of a disappointment for me as these are beautiful native prairie species. A moss phlox with pink flowers is chosen over the native Hood’s phlox with white flowers. The yellow flowers of the rudbeckia or black-eyed Susan are deemed “"too bright" and replaced by the scarlet and gold flowered gaillardia or blanket flower.
A hole of suitable width and depth is dug for each plant. After planting, soil is carefully tamped around the base to leave a slight depression where moisture can accumulate. For the first week or so, the plants need regular watering with a hose, about every day or two, to help them cope with the stress of transplanting. This is soon extended to every three or four days. Watering too frequently will stimulate root growth only at the surface instead of encouraging roots to extend deeper in search of soil moisture.
A few days after planting, a dump truck load of mulch is hauled to our front yard and spread over the bare soil to a depth of ten to fifteen centimeters. Earthlings chooses to use a bark and wood mulch of Douglas fir from British Columbia, instead of the traditional cedar. Kirsten prefers this as the Douglas Fir mulch is heavier and not as prone to being carried by the wind, it does not fade to grey, and because of its lower acidity it is less likely to absorb soil nutrients during decomposition. We anticipate periodically having to replenish the mulch as the plants grow to fill in empty spaces in the garden. Because this is a new product, its longevity relative to cedar is not known; hence, this is an experimental aspect to our landscaping project.
At this point we take time to admire the new garden and find it pleasing to the eye.
8. Planting the Turf
A few weeks pass before Kirsten and I meet to decide what grass seed we will plant in the area designated as turf in our design. I do not want to use Kentucky bluegrass and creeping red fescue as these are water greedy and need regular mowing. We want something that is drought-tolerant, short (less than 20 cm leaf length) and that will fill in to have the appearance of turf. I take a trip to a demonstration site at the Agriculture Research station east of town to see a plot of sheep fescue and another plot with June grass. Bare spaces between the clumps of grass are colonized by weeds.
We have both researched what native grass seed is available. We look at images of the various species. Mixedgrass prairie reclamation seed mixes provided by Pickseed, a local company, include wheat grasses and green needle grass which grow up to 100 cm tall. In the end we decide to experiment and do a dense planting of blue grama grass (Bouteloua gracilis). Its maximum height including seedhead is about 30 cm. It is a native species adapted to semi-arid prairie. Although a bunch grass, it can develop short rhizomes especially in the northern part of its range. Furthermore, I like the appearance of the purple, toothbrush-like seed heads.
Kirsten purchases a bag of blue grama seed from Pickseed. Because the seeds germinate best in warm soil, we decide to scatter it right away, at the height of summer. This is an experiment. Kirsten scatters the seed in sufficient quantity that it is obvious to the eye. On one side of the flagstone path the soil is raked in. On the other side it is rolled. The soil is moistened with a mist of water. I repeat the misty watering twice a day for the next four days with a hope and a prayer that this experiment will yield the results we want.
And After Winter....
The blue grama seedlings did not survive the winter. During April and May 2009, I identify Kentucky bluegrass, creeping red fescue, quack grass, dandelions, creeping bellflower and weedy annuals such as flixweed on the turf area but no blue grama grass. I dig out some of these and use spot application of glyphosate to eliminate those with deep rhizomes. I am told by a prairie restoration specialist that perhaps the planting occurred too late in 2008 for deep roots to establish.
We decide to try seeding again after further researching appropriate techniques and confirming adequate viability of the remaining seed. On June 1, when we are confident soil temperature is above 10 C, we vigourously rake the entire site by hand and smooth it with a heavy water-filled roller packer. We then plant blue grama grass seed by hand, scattering about 1.5 kg over the 45 m2 (0.2 kg/m2). The seed is lightly raked in to a depth of not more than 1.5 cm, with 10-30% of the seed still on the surface. The site is roller packed again to ensure good soil to seed contact. Immediately after we irrigate with a sprinkler to the point of small ponding and continue to do so every few days for the next few months.
Within a few weeks there is sufficient seed germinated to give the ground a soft green hue. By the end of June the fine leaves have grown a few centimeters and by the end of July the grass is about ten centimeters and emerald green. I monitor for weeds regularly and pull any forbs or unwanted grasses. There is a fairly continuous cover of blue grama grass in most of the seeded area with bare patches occupy about ten percent. We may need to seed these patches of bare soil next spring if they do not fill in on their own. Alternatively, it has been suggested that mowing the blue grama grass a few times may stimulate production of short rhizomes to fill in the unoccupied spaces.