JARS v50n4 - Evergreen Azaleas in Southern Ontario

Evergreen Azaleas in Southern Ontario
Nancy H. Traill
York University
Toronto, Ontario Canada

A bias in favour of evergreen azaleas is nothing to be ashamed of, nor is the conviction that they deserve more testing in Southern Ontario. Well selected and properly sited, they belie their reputation for tenderness and put on a spectacular show from April to July. Thanks to several breeders there is a good selection of fine plants bred for cold hardiness.
As things are, evergreen azaleas are underused in Southern Ontario. Some of the reasons are obvious - conservative landscape designers, conservative growers, institutions who rely on both, and horticulturists who are not yet acquainted with the needs of these plants. And, as in many other places, people do not always know their own growing conditions.
The part of Southern Ontario that I can speak about with confidence lies in the Great Lakes basin, stretching west from Toronto to Lake Huron. It is commonly called the "Carolinian" zone of Canada and ranges from 41 to 43 degrees north latitude, with Toronto at 43 degrees 45 minutes north latitude. In spite of the intensive farming in this area, one can still find the native southern hardwoods for which it is named: Cornus fiorida , Cercis canadensis , Liriodendron tulipifera , Magnolia acuminata and so on.
The area covers USDA Zones 5 to 7, with adequate to plentiful rainfall, though with occasional drought in the summer. My own experience is confined to a part of the city of Toronto along the shore of Lake Ontario, where USDA Zone 6/7 conditions prevail. The extremely deep waters of the Great Lakes, which almost entirely surround Southern Ontario, are a great climate modifier; they do not freeze in winter (except for the shallow Lake Erie) and act as heat basins, warming the surrounding land. For instance, in Toronto there is only a 17 percent probability that the January low will reach into USDA Zone 6a; there is a 70 percent chance that the winter will lie in the range of Zone 6b to 8a, with 6b having the highest probability.

Azalea grouping at the 
Toronto home of Laura Grant.
Azalea grouping at the Toronto home of Laura Grant
Photo by Laura Grant

But I know others who have grown evergreen azaleas with fair success in Orono, Ontario (Zone 5b), and even in Zone 5a, in Orleans, near Ottawa, and within Ottawa itself (the Dominion Arboretum) in spite of severe minimum temperatures during the 1993-94 winter. Anyone who would like more specific information about our conditions, to see if they are comparable to their own, is welcome to contact me directly.
The soils of Southern Ontario are mostly rich tills, ranging in structure from sandy and well-drained, north of Lake Erie, to the poorly drained gleysols of the Niagara, to the varied sand and clay of Toronto. They are usually neutral to slightly alkaline, but some are acidic. In any case, drainage, texture and acidity in one's garden can be gradually altered, if necessary, by the addition of humus, peat and sulfur.
A few specialists are beginning to experiment with evergreen azaleas, but because they are not widely grown here, generalizations are tricky. I will be specific, then, about my own experiences and hope they will encourage others to grow them outside the traditional "azalea belt" of the U.S. South.
My garden lies on a ravine near the Scarborough Bluffs, in Toronto. The native soil is a silty loam with a pH of 6.4 to 6.9. Only part of the garden was amended with mushroom compost (which I do not recommend because it can be saline), pine bark and peat. Though some of my rhododendrons are slightly chlorotic, the evergreen azaleas, with the exception of 'Elsie Lee', seem content. However, I now fertilize twice a year - in the spring and early summer - with a high nitrogen fertilizer because of the greedy roots of nearby maples. In another part of the garden where azaleas are grown, they prove their resilience in a different way: the spot is visited nightly by raccoons and is part of squirrels' run to their feeding box. Not only are the azaleas not bothered, they thrive in a soil that has by now been compacted by their countless comings and goings.
Winter exposure is perhaps greater than optimal; in bad winters, like '93-94 (cold) and '95-'96 (dry), evergreen azaleas can drop some leaves or become burnt. If sheltered from the wind, they tolerate some winter sun.
The features of evergreen azaleas that make them special, to me at least, are easily summarized:
1.  They are forgiving of summer heat and humidity, and the flowers are less prone to wilting than deciduous azaleas. At 86°F/30°C the summer blooming 'Balsaminiflorum' and 'Tachisene'* still look fresh.
2.  The leaves to not mildew, unlike those of deciduous azaleas.
3.  Plants can be selected to have flowers from spring to mid-summer, into late July or early August. Coupled with the heat tolerance of the flowers, this is a great asset.
4.  Many of them thrive in a fairly wide range of soil pH, 4.5 to 7.0.
5.  Their leaves are beautiful winter and summer.
6.  The flowers virtually smother the plants.
7.  The colour range is very large, with only yellow and blue excluded. Hues can be pastel, or they can be saturated, and whites are pristine. If you hanker after the colour peach, yet find rhododendrons with peach flowers too tender, you can have it anyway, by looking to the evergreen azaleas.
8.  There seems to be less of a discrepancy between plant and bud hardiness than one finds among rhododendrons. If it is cold enough to damage a rhododendron's leaves or wood, you are not likely to see flowers in the spring (though it can happen, and did after the '95-'96 winter). But even if an azalea drops leaves, it will generally go on to bloom.
9.  Squirrels seem to be uninterested in their buds, which are no larger than pips throughout the winter and (so my squirrel friends tell me) about as appealing.
Among the breeders' names one should watch for are Shammarello (Ohio), Gable (Pennsylvania) and Girard (Ohio); these men have worked to develop azaleas that will withstand temperatures of -20°F/-29°C. Some Glenn Dale (Washington, D.C.) hybrids are also good choices, and I have great hopes so far for 'Festive', which has white flowers, striped and sectored with dull rose.
The following is a list of the evergreen azaleas I have been growing long enough to make notes about their performance; except where another city is indicated, the azaleas are grown in my Toronto garden. Synonymous cultivar names are given in brackets; in parentheses are the breeders' names or, where this is not known, the hybrid group (e.g., Satsuki). Bloom times vary by as much as 2-3 weeks depending (of course) on weather. A warm spring will advance the times I give, which are derived from observations over the past few years when the springs have been unusually cool.
'Balsaminiflorum' ( R. indicum ). Three lovely specimens, all blooming very late (mid-June through July). They can drop some leaves if there's no snow cover, but they always bloom. Rosebud-like coral blossoms on a low plant.
'Ben Morrison' Two specimens: one, under a dripping eaves, was killed in the '93-'94 winter; the other, in an un-amended area, is cutting size and fine. The buds are more tender than the plant, but the colour is so exciting (white and salmon flaked, with a red speckled throat) it is worth the effort.
'Blaauw's Pink' (Kurume). Brilliant pink with a coral tinge, hardy, floriferous. Leaves tinged bronze in the winter. Blooms late May through June. Some desiccation after the '95-'96 winter, but the plant recovered well after a shearing (which prevented flowering this year, of course).

R. 'Blaauw's Pink'
Azalea 'Blaauw's Pink'
Photo by Laura Grant

'Bruce Hancock' ['Coral Cascade'] (azaleodendron, R. 'White Gumpo' x R. keiskei ) (Harris). A dud. Survived the '93-'94 winter under snow, didn't bloom, lost all its leaves in the mildish '94-'95 winter, didn't bloom. Chucked it.
'Cascade' (Shammarello). A popular white, with medium sized starry flowers that smother the plant in late May to early June. Hardy, a good-doer for many in Southern Ontario.
'Kirin' ['Coral Bells'] (Domoto; Kurume, one of Wilson's 50). A delightful surprise, one of the most exquisite with small, hose-in-hose coral-pink bells in great masses. Needs shelter (I put Christmas tree branches on it in January) and excellent drainage. It may lose some leaves but blooms reliably, though it probably cannot be counted on to be permanent. I find it slow growing.
'Corsage' (Gable). In Orono, Ontario, this plant is semi-evergreen, and has survived an absolute minimum of -33°F/-36°C. Flowers are an orchid purple.
'Dayspring' (Glenn Dale). I originally considered this plant, with its apple blossom pink flowers, neither hardy nor special. That was when it was sited with full exposure to winter sun and wind. It was since moved to full, high shade, in the squirrels' path, and is a treat. No desiccation after the '95-'96 winter and smothered in blossoms.
'Delaware Valley White' (a mucronatum selection or hybrid, classified among the Southern Indian hybrids). Hardy, incredibly floriferous, with white flowers smothering the plant. At its peak by the 1st of June for me, earlier if the spring is warm. A good-doer. It's only flaw is that the dead blossoms hang on as a flaccid reminder of past glory.
'Delicatissimum' (Domoto; old Kurume from Japan). Profuse white-centered blooms, flushed at the edge with soft mauve-pink. Shows colour in bud in early May, blooms from mid to late May into June. Rather slow-growing and not tremendously leafy; a good-doer none the less.
'Frank Arsen' (Gartrell). Pink with pale yellowish pink throat. Very beautiful and floriferous, but not heavy in leaf at any season.
'Girard's Karen'* (Girard). Rose, semi-double. Nice, but the lush foliage rather obscures the flowers. Probably destined to be a good-doer.
'Girard's Kathy'* (Girard). White, foliage covers the flowers a bit. Possibly another good-doer.
'Gumpo Pink' (Satsuki). A cutting that died during the '94-'95 winter. Probably worth trying again.
'Helen Curtis' (Shammarello). Always reliable with masses of white, frilly flowers in early to mid-June. Definitely a good-doer, leafy, unfussy, and with plant-smothering blossoms.
'Herbert' (Gable). A bright reddish-purple, fully evergreen in Toronto. It dies out eventually in Orono, Ontario.
'Hinode Giri' (Kurume). Though I have not grown this, it is reputed to be reliable, and I did see it in an Ottawa garden and at the Montreal Botanical Gardens in Quebec where, however, there is considerable snow cover.
'I'll Be Damned'* (Hager). Pastel pink semi-double ruffled flowers, very late (July). The flowers are very large, reminiscent of the Deep South, but so are the leaves. Some years, strangely, the leaves interfere with the flowers, other years the flowers stand out impressively.
'Kaempo'* (Fowle; R. kaempferi x 'Gumpo'). Luminous pink, reliable, flat-topped. Blooms mid June. A good-doer.
'King's Luminous Pink'* (King; an American Kurume). Bright pink with a lighter, star-shaped centre. Like 'Dayspring', did badly in winter sun and wind, but very well after its move into high shade.
'Marie's Choice' (Shammarello). Reliable white flowers in the colder climate (Zone 5b) of Orono, Ontario.
'May Belle' (Shammarello). Semi-double deep reddish pink flowers. Very much a good-doer in Southern Ontario; it withstood the bitter '93-'94 winter (coldest in 75 years, reaching -15°F/-26°C), and though the leaves were desiccated after the dry '95-'96 winter, it bloomed well and recovered very quickly. In Orono, Ontario, I am informed that the plant has survived for 15 years, but struggles.

R. 'May Belle'
Azalea 'May Belle'
Photo by Laura Grant

'Nancy of Robinhill' (Robin Hill). A June bloomer with hose-in-hose soft, clear pink flowers and a darker flare in the throat. Quite a beauty. I have found it hardy and reliable, though it died on someone else in Toronto.
'Pale Lilac' (Gable/Pride). Flowers reliably in Orono, Ontario, and has persistent (evergreen to semi-evergreen) leaves.
'Pink Pancake' (North Tisbury). Blooms late June to July. It loses leaves if exposed in the winter in my garden. In Orleans, Ontario, it survives with snow cover, as a semi-evergreen. The plant is almost a ground-cover. Flower colour is a difficult, dull, pink, brick-red. Or was, because I tossed it out.
'Rosebud' (Gable). Very bright medium-pink flowers like roses, blooms in June with Meconopsis grandis . Both of my specimens have been hardy and reliable. They have been neither for the plantsman in Orono, Ontario.
'Shinnyo-no-tsuki' (Satsuki). A July bloomer, if it feels like it, which in my garden it mostly does not. Huge flowers, white-centered with a purple picotee edge. Very low and must be covered with branches in the winter (but worth trying in areas with reliable snow cover). The buds are tenderer than the plant.
'Snow' (Kurume). Not a good-doer. Just tender enough to have its perfection spoiled (a little branch dieback), though mostly it blooms. I have found it better in shade. White hose-in-hose flowers are to my mind less beautifully shaped and positioned on the plant than 'Snowball'.
'Snowball'* (Kurume). A self-cleaning favourite of mine and a good-doer. A June bloomer, after 'Delaware Valley White'. Hose-in-hose white and profuse.
'Stewartstonian' (Gable). A bright red, new in my garden, but reliable for other people in Southern Ontario. Dies out in Orono, Ontario; is currently being tested in Orleans, Ontario.
'Tachisene'* (a double form of R. kaempferi ). Very late, blooming from late June or July into August. A few flowers can even be found in September. Flowers are salmon-orange, small and double like roses, and although the dead flowers stay on the plant until removed, they are bunched up neatly. This is a handsome azalea, if not quite as elegant as 'Balsaminiflorum'.

1.  Percentages are based on 76-year extremes for January for the city of Toronto.
2.  For information about the species, cultivars and needs of azaleas, one could not do better than to consult the revised and enlarged edition of Fred Galle's Azaleas (Portland: Timber Press).

The author thanks Mr. David Hinton, Orono, Ont., and Mr. Paul Boult, Orleans, Ont., for their valuable comments about the azaleas they have grown. Thanks are also given to Ms. Laura Grant, Toronto, for the generous loan of her slides.

Nancy Traill, a member of the RSC Toronto Chapter, is a professor of humanities at York University in Toronto.