NARGS- Alpine Gardening in Calgary

A Calgary Garden Through the Seasons

(Written by Rodney Shaver and Llyn Strelau for North American Rock Garden Society Bulletin)
Gardening in Calgary is a challenge. But, some of the very conditions that provide this challenge are the reasons that alpine and rock garden plants are the best and most logical choices for gardeners in this area. Sure we can grow a wide variety of annuals and herbaceous perennials. We can even vine-ripen tomatoes in a good season but in a more typical year the alpines are the reliable stars. We have lots of sun, adequate rain (or access to watering) in the summer, freshening breezes (well okay, sometimes gale-force winds), and cool nights. Our low winter precipitation means little problem with winter rotting, but this also means the lack of a reliable and persistent winter snow cover. Our frequent Chinook winds can raise the temperature by 30 degrees Celsius in a matter of hours. This can melt what snow we have accumulated and allow the intense winter sun to burn and dehydrate exposed plants or fool them into premature spring growth. (See chart for temperature and precipitation on a month-by-month basis). To protect our rock gardens from these undesirable conditions we first tried straw and evergreen boughs. One year of that was the last. Picking the remnants of straw out of alpine buns in the spring is not our idea of how to spend our time. Since then we have been using a thin insulating plastic blanket called MicroFoam that we lay down after we get a good snowfall (sometimes as late as the end of December). The trapped snow stays put until mid March or early April when the plants can look after them selves. The precocious drabas are sometimes in early bloom when we finally pull the cover off. The blankets are easy to work with and spring clean up is a breeze. We have reused the same blankets for 3 years now and should get at least another two before they need to be replaced.

Taken at CALGARY International Airport, Alberta. Elevation: 1077m

Averaged over the years: 1881 to 1990

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Temp. Daily Max (°C)	-3.6	-0.5	3.3	10.6	16.4	20.6	23.2	22.7	17.4	12.6	2.9	-2.3
Temp. Daily Min (°C)	-15.7	-12.3	-8.4	-2.4	3.0	7.4	9.5	8.6	3.8	-1.2	-9.0	-14.4
Extreme Max (°C)	16.5	18.9	22.8	29.4	32.4	35.0	36.1	35.6	33.3	29.4	22.8	19.4
Extreme Min (°C)	-44.4	-45.0	-37.2	-30.0	-16.7	-3.3	-0.6	-2.2	-13.3	-25.7	-35.0	-42.8
Precipitation(mm)	12.2	9.9	14.7	25.1	52.9	76.9	69.9	48.7	48.1	15.5	11.6	13.2
Sunshine (Hrs)	113.8	136.8	174.0	214.8	256.0	285.5	320.1	284.8	201.8	179.0	125.4	102.5

Total Precipitation: 398.8 (mm) Total Sunshine: 2394.6 Hrs

Alpines have an unexpected advantage over larger plants in Calgary as well. We live in: “hail alley… a corridor stretching across west-central Alberta that is North America’s most volatile hail zone. In an average year, about 40 major hailstorms roar down the foothills and pummel the alley, which includes Calgary…’ (Canadian Geographic, July/Aug 1998 pg68). It is a case of “the bigger they come, the harder they fall”. Delphiniums and lilies may look like they have been put through a food processor but most alpines will emerge from up to 6 inches of pea to golf ball size hail with only a few bruises.

Our soil pH averages 7.8-8.5 (higher in newer areas where subsoil is at surface) and tap water is 7.5. This alkalinity makes it very difficult to grow any acid loving plants. No matter how much peat, compost, or chemicals are thrown at the soil it quickly reverts to very alkaline conditions.

We are blessed with very few insect problems compared with more temperate areas of North America. Our low summer humidity and lack of deep winter snow cover make it a challenge for many insects to survive. We do have small slugs (introduced) that wreak havoc, and aphids, which can cause problems some years. The introduced grey squirrel can make a mess of the new growth of bulbs in the early spring or nibble, like mini-artichokes, the tender new sempervivum rosettes. In parts of the city there are problems with rabbits and deer. The most frustrating problem may be the birds! Some varieties like to pick the buns apart in the spring for lining their nests. Magpies and grackles will scatter or steal plant labels if they are visible.

We have both been avid gardeners for more than 15 years, but it has only been in the last five or six years that the ‘alpine bug’ has bitten us. In 1995 our first rock gardens was rather “forcibly” inspired by a gardening friend’s imminent retirement to the West Coast. She knew they were moving, but not when. To avoid losing any alpine treasures in an unseasonable move she decided that we should build a rock garden to house her plants until she had a new garden to put them in. We opted for a crevice style of rock garden. We had two loads of one-inch flagstone (local Rundle Shale, an attractive dark grey sedimentary rock) left over from pathway construction. We began with a mounded berm of soil excavated from the bog garden we had built that spring. Over the next two days our friend dismantled her garden and delivered the plants. We built up slabs of rock with a gritty compost of 10mm and smaller crushed shale mixed with the native soil. As the crevices were created we tucked her plants into their new home and top dressed with more of the crushed shale. The rock garden turned into a sensuously slumped and tilted berm fondly called ‘the sleeping giant’.

The berm wraps around the base of an old apple tree, with crevices facing north and west, and a south facing scree slope giving us several different exposures.

By the following spring we knew we needed another rock garden! This time we started at the west end with four large angular boulders, the heaviest weighing over one ton. Using these as a foundation we built a companion piece to our first crevice garden that mirrors it with the bog in between. This second crevice garden has the opposite orientation with the crevices facing the hot southern sun. We still needed more room so in 1997 we built third crevice garden to cover the 130cm tall knee-wall of our attached lean-to greenhouse. The south-facing section is the hottest and driest location and is a good environment for cacti and other alpines requiring full sun and well-drained soil. Where it wraps around the eastern end of the greenhouse we have a perfect spot for saxifrages and alpine primula.

It is difficult to list our favourite plants, but looking over our photographs and plant database, it seemed that each month we could find many plants in bloom. Here are some of the plants that have in the garden. We will discuss them in the order that they bloom for us in Calgary.

April

The first flowers in spring are Hepatica transsilvanica. Planted in the woodland garden their buds push up through the snow and bloom in the first week of April. When we see the large blue anemone-like flowers we know that spring is here, even though we may get several more snowstorms. The blooms of other Hepatica nobilis, acutiloba and americana and their forms quickly follow. Collecting Hepatica has become a passion and we have blue, white, pink and red plus a couple of double forms. In the rock gardens drabas provide cheerful colour in early spring. These vibrant yellow buns would be overshadowed if they bloomed later in the year but they are much appreciated first thing each spring. In very hot dry summers they go partially dormant for us but once the cool of late summer comes they revive and may even rebloom. The tight complex bun-forming species are attractive even out of flower. Among others we are growing:

Draba bruniifolia var. rigida (Ph.#16), D. olympica (Ph.#17), D. aff. Mollissima, D. cuspidata,

D. ossetica v. racemosa (one of the few with white flowers), D. ventosa, D. aizioides and D. caespitosa. Eunomia oppositifolia is equally early and its sweet honey scent is delightful. Douglasia montana (Ph.#15) A hot pink form that we received from a gardening friend, puts on a nice show in spring. Very few seedlings appear and looking for seed is like looking for the proverbial needle but it is slowly spreading around.

Saxifraga oppositifolia (Ph.#36,37,38) likes our cool spring but sulks in during the hot dry summers. We find that it does best with morning sun and afternoon shade. The form found in our mountains is not as large-flowered as some of the European varieties, but it is just as floriferous. One local grower has a small obsession with them and now has about 20 different varieties, each of them showing an amazing amount of difference in flower colour and form.

May

Who couldn’t love a gentian? The range of blues is stunning, from the smaller Gentiana verna ssp. angulosa (Ph.#19) to the almost artificial trumpets of the acaulis group. Our stock of “acaulis” is probably Gentiana angustifolia rather than true G. acaulis since it flourishes in our alkaline conditions. The friend who gave it to us had it self-sow all through her rock garden and even into her lawn until it formed carpets of blue every spring. Our alkaline soil and water makes it very difficult to grow the more acid loving fall gentians well.

Gentiana aff. acaulis, G. algida, G. bavarica, G. brachyphylla, G. dinarica, G. kurroo, G. loderi, G. paradoxa and G. septemfida are all successful.

Geraniums are not just for the perennial border. The smaller species and their varieties are wonderful tucked into crevices or at the base of larger rocks. The tuberous G. pylzowianum is quite delightful as it creeps along with its finely cut, 3cm wide, leaves and medium pink flowers that are large for such a diminutive plant. G. orientaltibeticum is a bit taller and the creamy-spotted variegation on the leaves is attractive even without it’s large white-eyed pink flowers. Geranium cinereum Ballerina grows to a better scale in a crevice than it does in the open garden. The foliage stays much tighter and the darker veined pink flowers bloom from May till frost. Geranium malviflorum is a bulbous species that blooms in the spring, goes dormant for the summer and produces leaves in the fall. Again it is compact with large flowers, and likes good drainage. Geranium sanguineum prostratum and its forms with deeply cut leaves and intensely coloured flowers are used around the edge of the rock garden and pathways.

Vitaliana primuliflora (Ph.#19) with its acid yellow flowers make a bold statement when combined with hot pink Douglasia montana and blue Gentiana verna!

Corydalis magadanica (Ph.#9) is a tiny tuberous plant that we received from Dr. Sasha Berkutenko three years ago. The curious flowers are a creamy white and last for several weeks in early spring. We have two plants in a tight crevice. One goes dormant at least three weeks before the other one, which was quite alarming the first year! It was a pleasant surprise to find it appear again the following spring. It goes to show that you should never give up on plants too soon! Having had good luck with C. solida & C. ambigua we are looking forward to growing more of these fascinating little plants.

Calgary seems to be an ideal place to grow Lewisia. Generally our dry winters keep them from rotting while dormant, although Lewisia tweedyi (Ph.#24), even when planted in a near vertical crevice, can rot during a very wet spring. Sometimes a piece of the root remains alive to regenerate once it dries out. Lewisia pygmeae can become somewhat weedy in it’s seeding around but it is easy to pull out the extra volunteers. It blooms off and on through the summer. Lewisia rediviva is stunning in a crevice with its huge flowers. It too has self-sown and we have both dark and light pink forms. Lewisia nevadensis and L. columbiana ssp. rupicola and wallowensis grow well in a climate quite unlike their native home. We are very excited with some of the Lewisia hybrids. Their compact size, lots of good size flowers over a long season, and vigour have made them favourites. Lewisia x Little Plum (Ph.#27) has narrow flat leaves with upright flowers stems holding a cluster of plum coloured flowers. Lewisia x Pinkie (Ph.#28) is similar with a pleasing soft pink flower. Lewisia x Flora’s Delight (Ph.#26) has smaller flowers but lots of them in a spray. Lewisia x cotyledon is represented in several colour forms; the Ashwood hybrids are particularly pretty and very floriferous.

The alpine Penstemons reach peak bloom here throughout May and June depending on the species. P. pinifolius is near the top of our favourite plant list. It’s delicate looking needle-like foliage survives our unpredictable winters without any damage and seems to grow best in the most difficult and exposed locations. Both the bright red of the species and the soft yellow of var. Mersea Yellow have a main flush here in June and then a generous smattering of bloom right until frost. Penstemon davidsonii var. menzii (Ph.#30) and its form microphyllus are wonderful ground and rock hugging shrubs. The huge flowers on such tiny plants always amaze visitors. Penstemon x Pink Holly (Ph.#31) is a beautiful pink variety that, like P. fruticosus, is wintergreen and prefers good snow cover for the winter. Fortunately they seem to regenerate from the crown even after a bad winter. Penstemon nitida, our prairie native, blooms and self-sows happily in dry sunny scree.

Lepidium ostleri (Ph.# 23) and L. nanum are two little gems forming hard dark green buns that are attractive even when not covered by a mass of white to cream blossoms.

We bought three plants of Clematis columbiana var. tenuiloba (Ph.# 8) three years ago. We assume that they were seedlings, because although the flowers are nearly identical in all three, there are definite differences in their growth habits. The best form is less than 6 inches tall with masses of full-size rich blue pendant bells and has a very short internodal growth. The other two are both taller and rangier. They all seem to be very vigorous in growth and if they weren’t so attractive could be accused of being invasive. They are planted at the base of two of our crevice gardens and have sent runners down and under large rocks to pop up in crevices several feet away. Clematis hirsutissima (Ph.# 7) is a much quieter plant with its feathery foliage and solitary leathery drooping bells.

June

Dianthus pavonius (Ph.#13) is one of the many dianthus that we grow and love. We enjoy the many surprises we get from the self-sown seedlings that appear in between the flagstone of our pathways. Ptilotrichum spinosum roseum (Ph.#33) is a 6-inch sub-shrub looks wonderful with its light grey-green hummocks of foliage against the dark grey of our Rundle Shale scree. The paler flower colour of the species is not as exciting as the deeper hot pink variety but the full range of a swarm of self-sown seedlings forms a beautiful tapestry.

Many Aquilegias are a bit large for the rock gardens but the more compact ones are lovely. These small plants have finely cut foliage and some have very blue-grey leaves, which contrast wonderfully with our dark grey shale. Aquilegia scopulorum (Ph.#6), Aquilegia (jonesii x saximontana), Aquilegia glandulosa and Aquilegia laramiensis have all found a home in our crevices. We have tried and killed enough A. jonesii that it is one plant that we won’t inflict ourselves on again. Yet some of the other Calgary gardeners have had very good luck in their conditions.

Jurinea moschus ssp moschus palandokan (Ph.#22), a monocarpic plant, caused an immense amount of comment this spring. The perfectly symmetrical rosette has a triffid-like presence as the leaves rapidly expand in the spring to reveal from the centre a huge stemless lavender thistle-like flower. After the central flower was spent many side growths from around the base took over, perhaps ruining the symmetry but giving a long season of bloom.

When we first bought Cytisus hirsutus demissus (Ph.#10) with its softly hairy leaves we doubted that it would be hardy in Calgary. We were pleasantly surprised when the next spring it was covered with bright golden yellow flowers. This form has been slow to spread but makes a nice carpet crawling among the rocks.

Dodecathion alpinum (Ph.#14) is only one of many shooting stars that share the garden. Most of them are in our bog or a north facing scree. We usually have to make sure to give it a little extra water in the spring to get it to flower well.

We are trying several Daphne species. Daphne arbuscula Muran (Ph.#11) has held its own in a quiet corner of a north scree, while D. cneorum fills another nook with its rich fragrance.

Ranunculus parnassiifolius (Ph.#34.35) in its pure white form now has many stems every year. It has started to sow around the mother plant so we look forward to a good colony.

Oenothera caespitosa v. marginata (Ph.#29) blooms all summer from June to hard frost in September. It is somewhat out of scale of the rock garden but the sight of 30 or 40 pristine white fragrant flowers opening in the evening is hard to resist.

Aethionema grandiflora (Ph.# 5) has very fragrant pink flowers atop glaucous blue foliage. Growing in some dry crevices we have been pruning them back to the newer more compact growth later in summer to encourage denser flowering plants next year. A. schistosum has extremely blue foliage that is a lovely contrast to our dark rock.

Acantholimons do quite well for us. They are growing in the most sunny and hot exposures and only exhibit problems if we have a prolonged wet spell. Acantholimon reflexosum (Ph.# 4) has very stiff prickly blue foliage and the large silvery bracts remain after the pink flowers fall. A. hohenackeri and A. litvinovii also have blue foliage while A. ercias is a shinier green spiky dome and all are doing well for us.

July - October

By July most of the alpines are finished their peak blooming. Several species of Calochortus will still bloom and some of the later penstemons are coming into their own. Callirhoe involucrata is just getting into full swing with its eye-catching wine coloured flowers on trailing stems. The summer colours of the sempervivums are pretty and the rock garden is all about patterns and texture. As the cool nights begin towards the end of August some of the alpines may decide to rebloom. It is also the time that the Saxifraga oppositifolia begin to look a little greener and may even put on a little bit of fresh growth. Some of the plants that will keep blooming for us till frost are Oenothera caespitosa, Erodium carvifolium, Geranium Ballerina, and Penstemon pinifolius.

As we head into September and October the nights can be very cool and some of the fall bulbs start to bloom. We have had very good luck with the earlier Colchicums like C. bornmuelleri as it has starts to bloom in early September most years. We have tried Crocus sativus, C. speciosus but they bloom too late in the season to enjoy them in all but the warmest autumns. Leucojum atumnale was a new acquisition this spring and it put on a respectable show for such a tiny plant.

As we head back into another winter and the garden is put to bed our dreams turn to the coming spring. There are so many more plants to try and holes to fill where other plants didn’t quite make it. We are very interested in pushing the boundaries of what we can grow here. We have begun collecting various dwarf conifers in the genus Picea, Tsuga, Chamaecyparis, as well as some dwarf evergreen Cotoneaster, and Buxus. Most of these need to be protected from winter sun and chinooks, but seem to be cold temperature hardy. Another group of plants that we are testing for hardiness is the Cactacea. We are presently growing various forms of Echinocereus reichenbachii, Opuntia basiliaris, O. clavata, O. fragilis, O. humifus, O. imbricata, and O. polycantha with no problems. Also the South American cactus Maihuenia poeppigii has made it through one winter with no special care.

Except for the foam blankets to help keep a good winter snow cover, we don’t coddle our plants outside. Although we live in a nominal Zone 3a climate we are successfully growing plants that are rated up to zone 6 or warmer which goes to show that most of the plants haven’t read any of the books! And we aren’t going to tell them either.

Three years after we began that first rock garden, the friend who inspired its building is revelling in her wonderful new Victoria, British Colombia garden, restocked with pieces of her treasured plants that survived our stewardship. We were fortunate to have few losses (perhaps more a testament to the hardiness of alpine plants than our emerging skills!) We still swap plants with this gardener and with many more around the world as we continue to discover the fascinating world of rock and alpine gardening.

Biographical note:

Llyn Strelau is a Calgary jewellery designer who enjoys the jewels of the plant world as much as the mineral ones. He was born on a farm in the Parklands of central Saskatchewan and fondly remembers spring hillsides covered in tufts of Anemone patens and the later-blooming Thermopsis sp. Rodney Shaver grew on a small acreage in Southern Ontario. An only child he spent many hours tramping through the bush enjoying the woodland flowers. While both of their parents gardened, they were more concerned with feeding families than with ornamental plants. Rodney and Llyn moved to Calgary and started gardening, indoors and out, once they had yards of their own. Twelve years ago they met at a meeting of the local orchid society and have consolidated their passion for plants ever since. Rodney left a computer job in the oil industry three years ago and started Rundle Wood Gardens Ltd. It is presently a small, home-based nursery that is aimed at providing a unique collection of hardy perennials for Calgary, including species and small-flowered clematis, dwarf conifers, plants for shade and woodland gardens and rock and alpine plants.