JARS 49n4 - Rhododendrons in Newfoundland

Rhododendrons in Newfoundland
Todd Boland
St. John's, Newfoundland, Canada

In 1971, the Memorial University of Newfoundland initiated the present day Memorial University Botanical Garden. Originally, the garden had the title of Oxen Pond Botanic Park. The initial reason for developing the garden was to provide an area where both the University and general public could view and/or study our native indigenous flora. The task of developing this park was given to the recently retired curator, Mr. Bernard S. Jackson. Through Mr. Jackson's love of butterflies and particular garden interests, the "botanic park" became elevated to the status of a botanical garden. Today, the Memorial University Botanical Garden is a combination 110-acre botanical garden and managed nature reserve.

Newfoundland is the furthest north (in eastern North America) that one can cultivate Rhododendron and other associated ericaceous plants. To understand how these somewhat tender plants can grow in Newfoundland, you need to be given an overview of our climate. Contrary to popular belief, Newfoundland, particularly the eastern portion of the province, is not very cold in winter. The average January temperature is about 26°F, although at times the temperature can plummet to 0°F. Our first major snowfall does not arrive until around Christmas, but snowfalls are common well into April. However, it is also quite common for winter mild spells to reduce our snow cover to nil. Wind is a major pitfall since it always seems to be blowing. During the winter, average wind speeds are about 25 mph; hence, winter desiccation can be a serious problem for many evergreens. As if this was not bad enough, ice storms are also a regular feature of our winters.

Our spring is that grey season when winter tries to maintain a stranglehold on summer's advance. With our close proximity to the sea (the garden being within four miles of the coast), the end result is often two months of fog! The major cause of our delayed spring is the result of sea ice and icebergs that drift down from the Arctic to the Newfoundland coast via the Labrador Current. If the ice arrived in winter, it would not be so bad, but instead the ice arrives in April and May, and in some years icebergs can still be a common sight in July! Summer is fairly cool with days averaging in the low seventies, and it seems to rain about every third day.

Over the last 23 years, much of the garden's focus has been research to discover what plants can be successfully grown in Newfoundland. Over the years, the plant collection has grown to over 3,000 varieties. Early on, it was realized that Newfoundland's naturally acidic soils, cool summers and mild winters (our USDA hardiness zone is 6) should be conducive to the growing of ericaceous plants. The garden now houses 18 genera of ericaceous plants, the most notable being Erica (with 30 taxa), Calluna (with 50 taxa) and especially Rhododendron (with over 170 taxa). Since the early 1980s, trials have been conducted on these plants to determine which species and/or cultivars are suitable for growing in our rather harsh climate.

During the earlier years, the garden grew relatively few Rhododendron , concentrating instead on Calluna and Erica . Before 1980, there were only 11 taxa, eight of which were species. The collection slowly grew to 33 types by 1985. At this point, concentration was on the species types rather than hybrids. The real boom occurred during 1987 and 1990, when the collection soared to 158 varieties. Most of these were modern R. catawbiense hybrids with a scattering of lepidote species and primary hybrids. Today, the collection stands at 172.

The Rhododendron collection is grown in one of the four main beds. Originally, they were grown in the peat bed. This bed is devoted mostly to ericaceous plants, many of which are native to the Island. Obviously, Rhododendron are a natural choice for such a bed. Later, some were also planted in the woodland bed, again an ideal location since many Rhododendron naturally grow in forested areas. However, while the plants grew well enough, their flowering was rather shy. It seems that because of our often cloudy summer weather, Rhododendron actually bloom better in Newfoundland when grown in full sun. As time went by, and the collection grew, it quickly ran out of space. In anticipation of the 1990 Annual General Meeting of the Rhododendron Society of Canada, which the garden hosted, a rhododendron-heather border was constructed that contains over 60 Rhododendron taxa. The construction of extensive rock gardens allowed the garden to expand the growing area for rhododendrons. This area is ideal for the dwarf lepidote types, including our own native Rhododendron lapponicum , known locally as the Lapland Rosebay. The previous horticulturist, Dianne McLeod, was keenly interested in our native lepidote Rhododendron and did extensive research on this species. Her test plots in the garden were home to over 75 plants, about half of which now grace the rock gardens. They provide a real show-stopper in mid-May. In the summer of 1994, some of the dwarfest lepidotes, such as R. setosum , the dwarf R. mucronulatum , and 'Wren' gained a home in the newly constructed alpine house.

Many of the garden's early Rhododendron species were members of the lepidote group. Upon acquiring the first lepidote varieties, the garden was immediately attracted to their dwarf habit and floriferous display. By growing many species and hybrid lepidotes, the garden extends its rhododendron blooming season from early May through to early August. In more recent years, many of the typical large-leafed rhododendrons have been grown. While quite beautiful, they do have a tendency to bloom simultaneously from mid-June to early July. Thus, the garden does rely heavily on the lepidote group to help extend the blooming season.

There are presently 50 Rhododendron species in the garden, 31 of which belong to the lepidote group. Also some 22 hybrid lepidotes are grown. While the lepidote Rhododendron account for only about a third of the total taxa, they are among the most floriferous rhododendrons I have seen.

Our rhododendron season usually begins in early May, although this may vary by a couple of weeks depending on the spring weather. The earliest species to bloom are R. dauricum , R. mucronulatum and our native R. lapponicum . In our harsh climate, the R. dauricum group are essentially deciduous. It is not uncommon for us to have a late snowfall while these rhododendrons are in full bloom, but for the most part such snow does little damage. Quick to follow these species is the R. dauricum hybrid 'Madison Snow'. By the first week in June, many more lepidote species begin to bloom, including R. impeditum , R. telmateium , R. russatum , R. nivale ssp. boreale , R. impeditum , R. tapetiforme , R. fastigiatum and R. intricatum . The lepidote hybrids PJM Group, 'Patty Bee', 'Wren', 'Tow Head', 'Ramapo', 'Ginny Gee' and 'Dora Amateis' also join in the revelry. By early June, the earliest of our elepidote hybrids are bursting forth their first blooms. Our earliest elepidote hybrid is 'Frilled Ivory'*, and, as the name implies, its flowers are indeed very ruffled and a beautiful cream, almost the shade of parchment paper. This hybrid is quickly followed by 'Carmen' and 'Scarlet Wonder'. I am particularly taken with 'Carmen' because of its prostrate habit, deep burgundy-red blossoms and its somewhat tubular shaped flowers. Mid to late June is the peak flowering season of the typical elepidote hybrids here in the gardens. The hybrids 'Grand Pre'* and 'Vernus' always seem to draw the most attention from visitors.

Meanwhile, the lepidotes are still undergoing a succession of bloom. 'Lavendula'*, 'Jenny'*, 'Tottenham'* and R. saluenense ssp. saluenense come into their own in late June. The hybrid 'Tottenham' is the most floriferous hybrid I have ever seen, the plants literally being smothered in bright pink blossoms.

The lepidotes continue on the blooming season through early and mid-July. Early July brings the flowers of R. ferrugineum , R. campylogynum Myrtilloides Group, 'Montifan'* and 'Laetevirens' (syn. 'Wilsoni'). Other relatively late rhododendrons include 'Wyandanch Pink' and R. camtschaticum . Finally, mid to late July starts the blooming season of R. minus Carolinianum Group and R. hirsutum 'Flore Pleno'*. In a recent summer, the last rhododendron did not fade until August 11! Our botanical gardens probably hold the record for having the latest rhododendron blossoms in the northern hemisphere. In total, our rhododendron season lasts for over three months.

While rhododendrons can be grown in Newfoundland, they do require some work. The larger elepidote hybrids require the greatest care since their height places them above the snow. If grown in a sheltered location, they can reach heights of over 10 feet, even in Newfoundland. However, exposed plants may be damaged by winter desiccation. To keep damage to a minimum, we have to place windbreaks of burlap around the plants or place teepee frames of latticework over them. The dwarf elepidote hybrids, and more especially the lepidotes, are the ideal choice for growing in Newfoundland since the snow covers them, providing natural insulation.

If any of you ever get the chance to visit Newfoundland, I strongly urge you to visit the Memorial University Botanical Garden, located on Mount Scio Road in St. John's, our capital. June and early July are the best months to view the numerous rhododendrons, but any time of the growing season will show a kaleidoscope of colors from the garden's beautiful plant displays.

Todd Boland, a native of Newfoundland with a master's degree in plant biology, has been an active volunteer at the Memorial University Botanical Garden since 1989 and has grown rhododendrons, especially dwarf lepidotes, for over 12 years. Currently he is the botanist with Murray's Horticultural Services in St. John's.

* Name is not registered.