Phenology of UBC Botanical Garden plant collections's Journal

For summer blooms, few plants are as diverse, yet instantly recognizable as members of the sunflower or daisy family, Asteraceae. With some 300 different types in the Botanical Garden, the family represents the greatest diversity of any group in our collections. There are annuals, perennials, biennials, shrubs and subshrubs, and they hail from every region of the world. This monthly dispatch could become the longest on record if I were to mention even a fraction of those that flower in the summer, so I’ll try to contain myself.

The sunflower itself, Helianthus annuus, is both an important crop plant and a common summer ornamental. This year, because of the sudden decline of the Koelreuteria paniculata (golden rain tree) and its removal at the front entrance last year, horticulturist Scott Ferguson elected to fill the space with large-growing annuals, including a raft of sunflowers. Though probably not ripening their seeds until later in September, these sunflowers should be expanding their impressive sun-following flower heads in August. Note that most plants in this family share the same morphology (form, shape, structure). The flowers are always gathered together into compact, usually flattened heads with the appearance of single flowers. Individual flowers are tiny and generally of two types, which is why plants in the family are traditionally called composites; i.e., composed of more than one flower type. So-called “ray flowers” are most often arranged around the perimeter of the head and have an expanded strap-like petal that radiates outward (like the rays of the sun), while flowers in the centre of the head have petals that are symmetrical but tiny. These central blooms are known as disc flowers because their numbers make up the flattened disc of the flower head. There are exceptions to this basic arrangement in the family, but the disc-and-ray pattern is common, especially among the ornamentals.

Close to the boardwalk (behind the welcome sign) is a planting of an exuberant sneezeweed, Helenium ‘Moerheim Beauty’. Despite the common name, Helenium pollen is transported by bees, and too heavy to be wind-blown. The name sneezeweed apparently arose because ragweed pollen, which is highly allergenic, is dispersed at the same time.  Although the David C. Lam Asian Garden holds relatively few composites compared with other sites in the Botanical Garden that have more sunshine, there are several of note here. For example, this year was one of the best ever for the July-flowering Inula magnifica (showy elecampane), and in the Physic Garden, Inula helenium (elecampane). We can expect the same from the early-August-flowering, low, fuzzy-leaved, Inula hookeri (Himalayan elecampane) (Farrer Trail and Lower Asian Way), and a tall selection of another Asian Inula species, the monumental Inula racemosa ‘Sonnenspeer‘(giant elecampane) (Upper Asian Way and Decaisne Trail, near the Asian Garden entrance). A close look at the any of these beautiful golden flowerheads reveals their classic composite construction.

Two composites dominate the Garry Oak Meadow Garden at this time of year: the near-ubiquitous Achillea millefolium (yarrow) and Grindelia hirsutula (hairy gumweed). The yarrow’s white flower heads are composed of tiny ray and disc flowers that have a musty smell, but they are important for beneficial insects. Gumweeds, too, attract a wide variety of insect pollinators. They are exceptionally drought tolerant, with sticky, bright yellow, rayed flower heads. Note also the curved, rubbery green bracts (a bract is a leaf-like organ associated with a flower stem) situated at the base of the flower head. Composites all have them: a set of bracts that protects the individual developing flower heads, then serves as a receptacle for the maturing seeds. The number of bracts and their various morphologies is often diagnostic for distinguishing between groups within the family.

While there are few composites on display in the Pacific Slope Garden, there is one in particular—western coneflower, Rudbeckia occidentalis—that deserves a second look. Rudbeckias are known for their often-substantial, brown, cone-like flower heads. Disc flowers are situated on the cone, and most species also have ray flowers around the base, but western coneflower has no rays. What it does have is a set of green, petal-like bracts at the base, where you’d expect the rays to be. A ring of yellow pollen-bearing anthers indicates the open flowers. The individual flowers are tiny, but popular with bees and butterflies.

The Food Garden hosts a wide variety of plants in the sunflower family (not least, sunflowers), but perhaps less obviously, lettuce (Lactuca sativa) and endive (Chicorium endivia), which are harvested prior to flowering—so, not particularly obvious members of the family. Calendula officinalis (pot marigold), a common Food Garden plant, definitely is recognizable as a sunflower relative. The bright orange ray petals are edible and the flowers attractive to beneficial insects. The wild-type of the species has daisy-shaped flowers, but most cultivated calendulas have “double flowers” with extra ray flowers produced where there are normally only disc flowers. So much the better for salad making. From the Food Garden, it’s only a few steps to the south-facing deck of the Garden Pavilion where a spectacular pale-purple display of Eurybia x herveyi (Hervey’s aster) awaits. Head over to the Carolinian Forest and the south-facing side of Lawson Grove to see an ever-expanding patch of Symphyotrichum novae-angliae (Michaelmas daisy). Michaelmas, a Christian festival, is celebrated on September 29^th, but our plants clearly don’t follow the liturgical calendar; they start to flower in late August. Both Eurybia and Symphyotrichum were originally classified in the genus Aster.

Renaming in composites is an all-too-common occurrence. The summer-flowering Pentanema ensifolium (sword-leaved elecampane), for example, was originally named Inula ensifolia. It looks as much, with its large, sunny flowers displaying numerous, slender rays, but the plants are more diminutive. Look for it in the bed to the west of the Roseline Sturdy Amphitheatre facing Deborah Butterfield’s Columbia (the horse), and along the path toward the Sanctuary Garden. Also on this path are plantings of cotton-lavender, Santolina pinnata subsp. neapolitana, an evergreen subshrub from Italy. Like all our cultivated santolinas, these form billowy mounds and are smothered in musty-smelling, button-like flower heads in summer. Ours is an English selection, ‘Edward Bowles’, which has attractively dissected leaves and pale sulfur-yellow, ray-less flowers. There is another planting of this cultivar behind the bulb frame in the E. H. Lohbrunner Alpine Garden, and a vibrant-green-leaved, yellow-flowered, Santolina rosmarinifolia subsp. rosmarinifolia (green cotton lavender or holy flax) in the European section, and which is visible from the ‘Edward Bowles’ planting above the Amphitheatre.

Across the Service Road from the Asian Section of the Alpine Garden (part of the Contemporary Garden’s plantings) are several substantial groupings of the globe thistle, Echinops ritro ‘ Platinum Blue‘. Particularly attractive to bumblebees, its ray-less flowers are imbedded in chaffy, ice-blue spherical heads. The smaller-growing, but more formidably-spiny, thistle-leaved daisy, Berkheya cirsiifolia, will be in bloom well into August. Likewise, the yellow daisies of the false gerbera, Haplocarpha scaposa. Both are in the African Section of the Alpine Garden.

There are some 136 different composites in the Alpine Garden, a collection dwarfing the numbers in other parts of the Garden. Here is a (very restrained) sampling: Look in the North American section for the pink-turning-white daisies of the delightfully airy Mexican fleabane, Erigeron karvinskianus, the delicate New Zealand mountain daisy, Celmisia gracilenta in the Australasian section, and the furry, dissected foliage of the prostrate silver tansy, Tanacetum haradjanii, in Asia Minor and the Trough Courtyard. The tansy deserves close inspection, whether or not it has its flattened, yellow-button-flowerheads. I suspect that visitors will be able to check off many more composites that I haven’t mentioned on this or any route through the Garden, as well as see hundreds of other summer bloomers along the way.

By Douglas Justice, Associate Director, Horticulture and Collections

https://botanicalgarden.ubc.ca/august-in-the-garden-2024/ 

A summertime visit to the Botanical Garden is a singular pleasure. When the temperatures finally rise to something resembling summer heat (hopefully this will happen in July), the forested paths of the woodland areas of the Garden beckon visitors to enjoy a cool respite from the sun. It’s easy to while away the hours sitting on a bench by a pond watching the antics of birds and dragonflies. In the shade of the David C. Lam Asian Garden, cranesbills (Geranium), astilbes (Astilbe), rodgersias (Rodgersia) and fairy wings (Epimedium) fill gaps between rhododendrons, deciduous trees and tall conifers. Rhododendrons are seldom thought of as summer bloomers, but the Garden has a number of July-flowering species, including the iconic Rhododendron auriculatum, with its long leaves, auriculate (ear-like) leaf bases, and sticky, fabulously-sweetly-scented, white or pink trumpet-like flowers that emerge in late July (south end of Wharton Glade). Somewhat earlier is another Chinese species, the equally impressive and even more tree-like Rhododendron glanduliferum (scattered plantings along Lower Asian Way from Purdom Trail to Kingdon Ward Way) with its oil-of-wintergreen-scented flowers.

Hydrangeas, much valued for their summer-borne blooms, are in evidence in the Carolinian Forest Garden, Contemporary Garden and Asian Garden. The Botanical Garden has some 160 different hydrangeas and hydrangea relatives in its collections. The family, Hydrangeaceae, which includes trees, shrubs, climbers and herbaceous perennials, is characterized by shade tolerant plants, though there are a few notable exceptions. The bush anemone, Carpenteria californica, a prominent shrub in the North American section of the E. H. Lohbrunner Alpine Garden, for example, displays its huge pure white blooms in late June and July at UBC.

The Contemporary Garden is home to a significant collection of Hydrangea macrophylla (common hydrangea) cultivars on the north side of the Arbor. Prominent among them is the ever-popular Hydrangea macrophylla ‘Mariesii Perfecta’ (blue wave hydrangea). Although still small, a good number of newer additions are starting to flower. Some 50 different, primarily “mop-head” cultivars—a gift of the local hydrangea nursery, Heritage Hydrangeas, in memory of its owner, Barry Roberts—will provide summer colour for years to come.

Climbers assigned to the genus Hydrangea include both evergreen and deciduous species—most of them white-flowered, but all of them handsome (notwithstanding the recent freeze damage to a couple of evergreen species). The “wood vamp,” Hydrangea barbara (previously known as Decumaria barbara), is an eastern North American “self-sticking” deciduous climber that produces its flowers in July. Look for it on trees throughout the Carolinian Forest plantings, though the largest is plastered to the north side of a black walnut, Juglans nigra, in Catesby Grove. Plantings of the oakleaf hydrangea, Hydrangea quercifolia and silverleaf hydrangea, Hydrangea radiata are in the Carolinian, as well, and blooming at either end of Fraser Grove. At a somewhat grander scale, Hydrangea hydrangeoides (formerly Schizophragma hydrangeoides) ascends trees in the Asian Garden and also blooms in July. There are several plantings throughout the Garden, but the specimen on Upper Asian Way near Wharton Trail is truly impressive.

Herbaceous hydrangeas include species previously known under the name Dienanthe. A lovely patch of the low, pale-blue-flowered Hydrangea caerulea can be found in the Asian woodland section of the Alpine Garden. The closely related Hydrangea bifida, with lighter-coloured flowers, is given somewhat more space in the Asian Garden (around where Straley crosses Campbell Trail). Both are readily recognized by their unusual-looking bilobed leaves. The most impressive of the herbaceous hydrangea relatives is arguably the East Asian Kirengeshoma palmata. Japanese seedlings grow to about 1.5 m (5 feet), while our more robust Korean collections top out at more than 2.5 m (8 feet). Two plantings (the Japanese and Korean) face each other across Upper Asian Way just short of Straley Trail. The stems on both types carry opposite pairs of broad, jagged-edged leaves and are surmounted by waxy, tubular yellow flowers that dangle on wire-like stems. The flowers and are visited by all manner of bees, butterflies and hummingbirds, and admired by all who see them.

By Douglas Justice, Associate Director, Horticulture and Collections

https://botanicalgarden.ubc.ca/july-in-the-garden-2024/ 

I should start this month’s despatch by correcting a mistake from the May 2024 in the Garden entry, which stated that Rhododendron decorum subspecies diaprepes ‘Gargantua’ “started flowering in mid-April,” which it did not. As is its normal habit, it will be in glorious bloom in June. Mea culpa. In my defence, I was still jet-lagged and fuzzy-headed after my return from Japan. Anyway, I should know better, as my father named a particularly floriferous diaprepes seedling in his garden ‘June Wedding’. Two closely related species, Rhododendron glanduliferum and Rhododendron serotinum (examples of both species along Lower Asian Way between Kingdon Ward Way and Purdom Trail) will similarly extend the season for large, fragrant, white-flowered rhododendrons. Rhododendron glanduliferum is named for the conspicuous stalked sticky glands that clothe its new growth, and R. serotinum for its late-emerging flowers (serotinus = late).

There are several more June-flowering rhododendrons in the Asian Garden, including an array of evergreen azaleas. Most are Japanese cultivars of Rhododendron indicum (satsuki azalea) and are located at the highest point on Fortune Trail. In the E. H. Lohbrunner Alpine Garden, azalea diversity is even more evident. Although the majority of azaleas will have bloomed prior to this month, a few are later flowering and are all Asian species or cultivars—hence, located in the Asian Woodland. Rhododendron nakaharae is a Taiwanese native azalea that typically produces flowers from June to August, sprinkling its low creeping stems with an exuberance of large vermillion to cadmium-red flowers. Why this is not a more popular ground-cover is a bit of a mystery, as it was introduced into North America more than 60 years ago. The unusual satsuki azalea Rhododendron ‘Yodo-no-hikari’ forms a dense mound of grass-green foliage that partially obscures its tiny white flowers. This is an azalea for people who want to steer clear of overt expressions of floral exuberance. The flowers have a vaguely honeysuckle-like appearance, and the cultivar is not without charm. More-unusual still is Rhododendron tsusiophyllum, a true dwarf azalea from Japan, that in June produces miniature, white tubular flowers no more than about 10 mm long.

The Carolinian Forest Garden boasts several late-flowering American deciduous azaleas. Although well adapted to garden culture, most are not common in gardens. Nearly all the North American azaleas are native to the Appalachian Mountains or the eastern US. Flame azalea, Rhododendron calendulaceum, produces its brilliant yellow-orange to orange flowers from late May to late June, depending on the preceding weather conditions. The species is planted along pathways throughout the Carolinian Forest Garden, so it’s not difficult to find when flowering. While the flame azalea is among the most eye-catching of the Appalachian species, the flowers have little or no fragrance. In contrast, the white-flowered Rhododendron arborescens (sweet or smooth azalea) is highly fragrant, the flowers smelling of cinnamon. The stature and form of the species, while not exactly arborescent (tree-like), is tall and attractively layered. There are plantings of this elegant species in Lawson, Marshall, Rafinesque and Tradescant Groves. The closely-related Rhododendron viscosum (clammy or swamp azalea) blooms around the same time, with pink-budded, long-tubed, sticky white flowers. Unlike the sweet azalea, which produces abundant displays of flowers every year, our clammy azaleas have been exceptionally shy to flower (the reason there are no images of same). Perhaps this year will finally bring them into their own, so that we can enjoy their strong clove fragrance wafting through the Garden in June. Look for it in Fraser, Lawson and Rafinesque Groves.  As I’ve mentioned previously, many later-flowering plants are blooming earlier than normal this year, and these azaleas may well be past flowering by early June. But take heart—there will undoubtedly be something to catch your eye in the Garden.

By Douglas Justice, Associate Director, Horticulture and Collections

https://botanicalgarden.ubc.ca/june-in-the-garden-2024/

Although April is the peak of rhododendron bloom in the David C. Lam Asian Garden, there are plenty more to come in May. The Azalea Glade, which is reached off of Henry and Fortune Trails, east of Upper Asian Way, holds a few treasures in this regard.  At least two forms of Rhododendron campylogynum should be flowering there in May: Rhododendron campylogynum Myrtilloides Group (very dwarf plants) and Rhododendron campylogynum Charopoeum Group (plants with larger flowers). The white-flowered Rhododendron ‘Leucanthum’ was once considered another variant of the species, but it has been deemed a hybrid.  Rhododendron oreotrephes is the picture of elegant understatement with its aromatic, small bluish leaves and lavender-mauve flowers. This species is in the same group as the flashier and more familiar R. augustinii. Steps away, the full-bodied orange flowers of the deciduous azalea, Rhododendron molle subsp. japonicum, command attention (whether orange is your thing or not). Along Upper Asian Way look out for the richly purple-flowered Rhododendron trichanthum, which is one of the later-flowering species in the R. augustinii alliance (technically, section Rhododendron subsection Triflora, which also includes R. oreotrephes).

The white- to rosy-pink-flowered Rhododendron qiaojiaense (“cheow-jee-en-see”) was only named scientifically in 2016, though plant explorers have known it as early as the 1990s in the wild in Yunnan, China. The phenomenal bud-set this year will translate into an outstanding floral display in May. There is a pair of small plants on Delavay Trail, west of Kingdon Ward Way and several larger ones along Hu Trail east of Sargent Trail, though the latter are still labeled as R. decorum subsp. cordatum (an early, provisional name). Described scientifically in 2008, Rhododendron qiaojiaense is a close relative of the larger-growing, Rhododendron decorum subsp. decorum. The finest of our “decorums” is located on Ludlow Trail, just above Lower Asian Way. The subspecies diaprepes is more tree like, and usually later to bloom, but ours, Rhododendron decorum subsp. diaprepes ‘Gargantua’ (a particularly arborescent, large-flowered selection), started flowering in mid-April. There are two plants, one north of Siebold Trail between Rock and Decaisne Trails, and an even taller one where Handel-Mazzetti Trail crosses Tschonoski Trail.

Several more in this stalwart group (subsection Fortunea) flower in May, with a few species normally opening their blooms as late as June or July. Rhododendron fortunei subsp. discolor may still have a few left in early May, but Rhododendron fortunei subsp. fortunei flowers are often emerging a week or so later. One of the finest selections of this species ‘Sir Charles Butler’, with palest pink flowers, is on Siebold Trail at Stearn Trail. All bets are off regarding flowering times after the winter we just experienced, but we can be sure that at least some of our magnificent Rhododendron glanduliferum (normally June-flowering with large white to pale pink, wintergreen-scented blooms), will produce a few good trusses in May. Multiple specimens are located along Lower Asian Way below Wharton Glade as well as on the west side of the path closer to Kingdon Ward Way.

Further to the south and east is Rhododendron maoerense, another tough, tree-like rhododendron. As with R. glanduliferum, there are conspicuous glands on the flower stalks, but the stalks in R. maoerense are longer and the trusses more open and upright. The flowers are larger and a strong rosy pink. Look for this species on Lower Asian Way at the west end of Soulie Loop and where Handel-Mazzetti Trail meets Meyer Glade. While visiting this part of the Garden, note that there are two deciduous magnolias here that regularly bloom in May. Magnolia sieboldii has nodding, cup-shaped flowers, while the closely-related Magnolia wilsonii has larger, more pendant blooms. Both smell deliciously of lemon blossom. The two are located next to each other, below Lower Asian Way south of Little Tsangpo Creek. They have multi-stemmed spreading crowns and broad leaves that hint at their tolerance for shaded spaces.

By Douglas Justice, Associate Director, Horticulture and Collections

https://botanicalgarden.ubc.ca/may-in-the-garden-2024/

2024 will go down as an exceptional year for ornamental cherries, but one of the least predictable for timing. For example, the flowering schedule outlined in the handbook Ornamental Cherries in Vancouver, published in 2014 after several years of careful phenological observations, has been mostly turned on its head.

Early cherries, like Prunus ‘Accolade’, are still blooming now (in the first week of April), when they typically flower in late February or March. This is a cherry that announces itself with confidence. Its delicate branching and wide spreading crown add considerably to its charm, but people are primarily attracted to the pizzazz of its semi-double, unapologetically bright pink flowers. ‘Accolade’ is a “modern” (i.e., 20th century) cross between the spring cherry, Prunus itosakura, and another Japanese species, Prunus sargentii, which is known in Japan as O-yama-zakura (big mountain cherry—for its large stature). There is a single specimen at the northwest corner of the Reception Centre. Prunus sargentii is normally a reliable bloomer in mid-April, but its flowers have been out for weeks. A group of three is located where Stearn Trail diverges from Upper Asian Way in the Asian Garden. Visitors may be able to see a few lingering flowers from these trees at the normal time, but don’t delay too long. Similarly, Prunus ‘Pandora’ usually opens its soft pink blossoms in mid-April—but not this year. This English hybrid was developed in 1939 by the famous cherry breeder Collingwood “Cherry” Ingram. ‘Pandora’ can be recognized now by its fine, twiggy stems and low-branched, upright form (and maybe still, a few soft-pink flowers).

Luckily, the rarely cultivated and mostly underappreciated cultivars, ‘Mikuruma-gaeshi’ and ‘Ichiyo’ are right next to ‘Pandora’, amongst the daffodils, north of the entrance roundabout. Both are known as sato-zakura or “village cherries” (so named because their origins are obscured by long cultivation around Japanese villages). ‘Ichiyo’ usually flowers in late April, but this year it will be in perfect form before the middle of the month. This ancient cultivar boasts robust growth and sublimely beautiful, soft pink, fully-double flowers. In a typical year, ‘Mikuruma-gaeshi’ follows ‘Ichiyo’ by about a week; however, this year, ‘Mikuruma-gaeshi’ was in full flight on April 1st (no joke). Known by the appropriately evocative “royal carriage returns,” ‘Mikuruma-gaeshi’ has both single and semi-double flowers nearly as large as those of the famously large-flowered “great white cherry,” ‘Tai-haku’. Close up, the exquisite flowers of ‘Mikuruma-gaeshi’ might just take a viewer’s breath away, as they have done since the 15th century in Japan.

There is a row of ‘Tai-haku’, another sato-zakura, west of the entrance to UBC Botanical Garden, parallel to Marine Drive. The single white flowers, the largest of any of the cultivated cherries, emerge from soft-pink buds, and the blossoms contrast with bronzy, barely-emerging leaves. Here, they are all grafted plants, and the overly vigorous commercial rootstock is causing all sorts of havoc; they exhibit the shallow roots and extensive suckering that is all too familiar with grafted cherries. Visitors should be able to recognize that there are significant differences between the grafted and un-grafted trees, not least that the grafted ones show a congested proliferation of scaffold branches at about 175 cm (6’) above the ground, while wider-spaced, more natural-looking branching characterizes un-grafted trees. Note that all of the cherries inside the fence at the Botanical Garden are growing on their own roots, and all of the remaining grafted ‘Tai-haku’ will gradually be replaced by own-root cherries, propagated at our own nursery.

Another of Cherry Ingram’s creations, Prunus ‘Umineko’, opens its white flowers after its grass-green leaves have already started to emerge. This year, the red hearts of the aging flowers are already visible in first week of April (i.e., two weeks early). A group of three of these densely-branched, strongly-upright trees is situated at the western end of the Wharton Cherry Grove, near the corner of the parking lot. The rounded petals apparently suggested to Ingram the feathers of a gull (umineko means “seagull” in Japanese). ‘Ojochin’ (large lantern) at the other end of the Grove, is another old (late 1600s) sato-zakura, though with large, somewhat inflated, lantern-like buds. These open lazily to display opulent, five-petaled flowers (often with an extra, incomplete petal) of the lightest pink.

Like ‘Tai-haku’, ‘Ukon’—a single tree, west of the trio of ‘Ojochin’—has an upright-spreading crown, but its smaller flowers emerge from pinkish buds and open with a yellow cast, as though barely dusted with turmeric (ukon means “turmeric” in Japanese). The flowers are also mostly semi-double—that is, endowed with a few extra petals. Normally opening coincident with ‘Tai-haku’, this year ‘Ukon’ will be at peak bloom in mid-April, which is strangely normal. ‘Gyoiko’ (harlequin cherry), sits a few trees to the northwest of ‘Ukon’. Considered a close relative (it probably originated as a branch mutation of ‘Ukon’), ‘Gyoiko’ blooms about a week later. Both cultivars were known before 1780 in Japan. The harlequin cherry’s extraordinary flowers are white, coloured with prominent green stripes, and backed by a purplish calyx (the collective term for the sepals), and the heart of the flower also sometimes develops purple-red streaks. The name gyoiko refers to a purple, white and green robe worn by noblewomen at court in ancient Japan.

Finally, the cultivar ‘Pink Perfection’ is always our last cherry to flower. A modern English sato-zakura hybrid, ‘Pink Perfection’ was discovered and named in 1935. It is recognized by its abundant large, white-centred, pale-pink, double flowers, and its lax, somewhat disorganized branching habit and generally untidy appearance. There is a small planting spanning both sides of the fence west of the Panabode Building (the old Botanical Garden entrance).

Life isn’t a bowl of cherries. Indeed, in April there are also plenty of rhododendrons, camellias, magnolias, maples, staphyleas, winter hazels, epimediums and more in the Botanical Garden bowl—so come and see for yourself.

By Douglas Justice, Associate Director, Horticulture and Collections

https://botanicalgarden.ubc.ca/april-in-the-garden-2024/