A Gardening Journal

'Sunburst' Hypericum

Hypericum-frondosum-Sunburst-073014-bees-good-640 

 

The bees vibrate with intensity as they work their way around the unusual "wreath" of yellow-to-amber stamens. The shiny ovary at the center, tipped by a pistil that seems as rigid as a toothpick, always seems to be ignored completely. And yet the shrub does set seed, forming reddish-brown capsules that are modestly showy.

 

Hypericum-frondosum-Sunburst-073014-blooms-and-buds-640 

 

The swelling greenish-yellow buds are the start of a flowering season that can last nearly two months. When not in bloom, Hypericum frondosum 'Sunburst' is a pleasure thanks to its blue-green foliage. Even when not in leaf, the show doesn't quit: Older branches have exfoliating bark, and develop a windswept angularity.

 

 

Here's a look at the intriguing branch structure of 'Sunshine' in full reveal in Winter. And here's how to grow this unusually agreeable shrub:

 

Latin Name

Hypericum frondosum 'Sunburst'

Common Name

Sunburst hypericum

Family

Hypericaceae, the Hypericum family.

What kind of plant is it?

Depending on the severity of the climate, an evergreen, semi-deciduous, or deciduous shrub.

Hardiness

Zones 5 - 8

Habit

Mounding and full to the ground, with attractive cinnamon-barked branches that develop an artistic gnarliness and irregularity with age. They are fully revealed in Zones 7 to 5, where weather is cold enough to cause shedding of foliage for the Winter.

Rate of Growth

Fast.

Size in five years

'Sunburst' is reported to be more compact than the species, and matures to about three feet tall and four feet wide; my old shrub is easily four feet high and six feet wide. Shorter in Zone 6a into Zone 5—the cold end of its range, in other words—where it might incur some tip die-back even in a normal Winter.

Texture

Pleasingly full without appearing dense or heavy.

Grown for

its flowers: Bright yellow, they are somewhat larger than those of the straight species, closer to two inches across than the one- to two-inch range of the species' flowers. The stamens form a bright yellow wreath around the large shiny ovary that is tipped, like some comical form of fez, by a central spiky pistil. The bases of the stamens are amber, suggesting additional coloristic possibilities for plant partners. 

 

its attractive foliage: The leaves are in opposite pairs. They are smooth-edged, with a distinct slate-blue bloom that, alas, can become smudged when leaves in adjacent clusters brush against one another.

 

its habit: As is typical of Hypericum, 'Sunburst' is naturally mounding and bushy. Because its branches develop attractive bark as they age, as well as bending ever lower with weight, the bushes don't need to be pruned so as to enhance the density of growth near the ground. Happily, comparatively erect new growth emerges readily from new basal stems as well as from the sides of now-leaning older stems, so that there's no need to prune to enhance fullness higher up, either. 

 

its tolerance of heat: 'Sunburst' is one of the few hypericums to thrive even in the Deep South, where most others in the genus succumb to nematodes or root rot, and high heat and humidity.

 

its cultural tolerance: See "Culture," below.

 

its lack of interest for browsers: 'Sunburst' is rarely even sampled by deer, let alone seriously chewed.

 

its appeal to bees: On a hot sunny day, two or even three bees can dance around a single blossom, in a frenzy of pollen and nectar foraging.

Flowering season

This is usually listed as June into July, but flowering continues into August for me. 

Color combinations

Because the foliage is distinctly blue and the flowers are bright yellow, 'Sunburst' brings plenty of color to any setting. Introduce additional colors with caution if the result isn't to be jumpy or, simply, thoughtless. Few other "blue" colors—which are often tending to lavender or violet or purple—will collaborate with the greenish blue of the leaves even though they would probably sing next to the flowers. (In contrast, almost any other shade of yellow would be compatible.) Although white is one of the universal mixers along with green and deep burgundy, unless there's also some yellow present in the partner plant's display of white, the effect will be one merely of juxtaposition, not conversation.

 

It's safest to surround 'Sunburst' with neighbors that enliven through contrasts in texture and scale, all helped along with foliage that's colorful and sometimes variegated, rather than through addition of contrasting colors. To my eye, the only color to add that is, at once, contrasting but not clashing, is burgundy. (If you can think of another plant that features amber in its Summer foliage, fruit, or flowers, you could create a subtle tie-in with the amber bases of the stamens.) The two obvious choices for exact matches in color—roses or dahlias—would be ruled out by too-similar geometry: Like those of 'Sunburst', their flowers are also round and the most dense at the base. Are there small flowers that are borne in spikes or racemes, have amber details, and are not radially symmetric? 

Plant partners

Provide a larger horticultural context for 'Sunburst' that does not rely on flowers, or even feature them. First, remember that 'Sunburst' flowers for many weeks, which few other hardy partners could sustain. Second, there's a prevalence of rose- or daisy-like flowers in the Summer, and they will look repetitious next to those of 'Sunburst' regardless of how well their colors harmonize.

 

'Sunburst' flowers appear singly or in clusters of just a few blooms held tightly side by side. So for floral partners, look for flowers that are dramatically smaller, and that are arrayed in complex groupings of scores or even hundreds. If the individual flowers are narrowly tubular and, like pea flowers, symmetrical only across a vertical plane, so much the better. These conditions are so specific they may finally goad me into growing Phygelius aequalis 'Yellow Trumpet'. And to plant nearby the comparatively restrained native honeysuckle, Lonicera flava. As the Latin "flava" suggests, something about this plant is yellow: the flowers, of course. Besides the phygelius, other helpful "spikers" include Kniphofia 'Bressingham Sunbeam' or 'Shining Sceptre', Sinningia 'Bananas Foster', and Verbascum densiflorum. Small flowers borne in large broad or rounded groups such as umbels, panicles, and corymbs would also be fool-proof: Consider Cassia corymbosa, Cestrum 'Orange Peel',  Patrinia scabiosifolia, and Buddleja x weyeriana 'Honeycomb'.

 

Setting a pot of 'Zinfandel' oxalis near a 'Sunburst' would be an easy double-hitter: Its yellow flowers are the same hue as the hypericum's but a fraction the size. And its burgundy clover-like foliage is a strong counter to the cool blue-green of the hypericum.

 

With the range of floral temptations introduced above, it would easy to overload the garden around 'Sunburst' with flowers. In itself, a profusion of blooms is always an achievement. But inevitably, a floral focus welcomes plants deficient in extra-floral abilities such as foliage texture and color, or season-long endurance. Better to include flowers just as the icing on the cake—and only after you've ensured that the cake itself is as spicy, juicy, and sturdy as possible. Begin with a yellow-foliaged conifer, as scarily bright in high Summer as your climate will permit. For me, that's Chamaecyparis obtusa 'Fernspray Gold' as well as Cedrus deodara 'Gold Cone'. Both are semi-dwarf, not more than eight to ten feet tall. Next, the dense, small, dark-green foliage of a columnar broadleaved evergreen, Ilex crenata 'Sky Pencil', thrusting through the white-yellow foliage of Cornus alba 'Aurea'. At the front, kept just barely at bay, a relentless colony of 'Geisha', the variegated form of Lysimachia ciliata. To the side, the spreading feathery mound of Acer palmatum 'Red Pygmy'

 

Only after such a diversity of partners whose display doesn't depend a bit on flowers is it time to add a few plants for whom flowers are their peak moments. At the back of my 'Sunburst', I've planted Ligularia palmatiloba, whose large orange-yellow daisies make the flowers of 'Sunburst' seem small, and whose tropically-big, toothy, green foliage is a show in itself. To the other side, my colony of Patrinia. Next season, the yellow Lonicera—plus, set on a stand so it can billow just barely above the 'Sunburst' foliage, that pot of 'Zinfandel'. 

Where to use it in your garden

The growth habit of 'Sunburst' is full, mounding, and regular enough that the shrub can be planted en masse to produce an informal but effective large-scale groundcover. With its tolerance of heat and sun, its hardiness, and its preference for excellent drainage, 'Sunburst' should be a prime candidate for planting in larger soil pockets in south- or west-facing ledge. In such a setting, would the branches' natural tendency to attractive sprawl produce a billowing cascade? It would be a thrill year-round. Although I wouldn't attempt it in climates colder than Zone 7, these same attributes could make 'Sunburst' an easy year-round subject for large, permanent containers.

 

'Sunburst' is also a big success when growing amid shrubs and perennials. Its tolerance of occasional pruning and its opportunistic outward growth enable it to work as excellent filler around more upright and, especially, columnar companions. By the same token, 'Sunburst' could be challenging to keep in bounds around shorter or less energetic companions.    

 

See "Plant partners," above for suggestions for plant combinations that synergize with the coloring, texture, habit, and soil and exposure preferences of 'Sunburst'.

Culture

'Sunburst' is reported as preferring alkaline soil, and is well known for its tolerance of drier soils that bake in the sun, including sandy ones. But the shrub seems to thrive in regular soil of almost any pH as long as the drainage isn't outright terrible. As proof, mine is in its sixth year, and has never shown a moment's hesitation even when growing in my heavy dead-level soil that offers only sketchy Winter drainage. 

How to handle it: The Basics

Plant in Spring or Fall, ensuring enough water for establishment.  The habit is naturally full and bushy, so routine or formative pruning is necessary only if Winter was harsh enough to cause dieback. Then prune after the shrub has started into growth, so that you can easily discern which sections of which stems have been winter-killed. Anything less than outright killing won't affect that season's flowers: They develop at the tips of new growth, and the bush resprouts easily and profusely, even directly from the base.

 

Because the bark of mature branches exfoliates, and those stems assume impressive writhing and cantilevering positions, routine pruning isn't usually recommended or needed. Further, the shrub's naturally mounding habit and semi-sideways branching ensures that there are plenty of new shoots from the side buds of those branches, which, in turn, ensures plenty of flowers.  

How to handle it: Another option—or two? 

Unusually for plants in my garden, 'Sunburst' is best when allowed to grow freely. There's no benefit to cutting back in Spring, say, to delay flowering: You'll only destroy the Winter interest of mature branches. And the plant's easy fullness and naturally-angling branches don't lend themselves to either staking for extra height, or renewal-by-pruning to recapture ground-level density. It's there all on its own.

 

As the planting in my beds becomes ever denser—there are always scores of new plants to try, but only so much more planting area to be created—my only intervention with 'Sunburst' is to remove a very occasional branch right to the base, to open up a scant square foot so that yet another tall and narrow shrub or perennial can soar skyward. Year after year, 'Sunburst' has changed from a full-all-around mound to a starfish-like array of major branches, each an arm of foliage and flowers filling an ever-narrower gap between taller neighbors. 'Sunburst' being 'Sunburst', the shrub's performance seems as willing and vigorous as ever. 

Quirks and special cases

None.

Downsides

Hypericums in general don't enjoy heavy soil, or high heat and humidity. Probably because there's plenty of clay soil and high heat where 'Sunburst' is native, it is among the most easy-going and durable of hypericums in climates where hot and steamy Summer weather is the norm.     

Variants

The straight species, Hypericum frondosum, is also worth growing, especially where its somewhat larger size is an asset, as would be the case in large-scale mass plantings. I'm not aware of any named forms of this species other than 'Sunburst' that are available in North America.   

Availability

On-line as well as at retailers.

Propagation

By cuttings, by division of older clumps, and by layering. 'Sunburst' doesn't come true from seed: Progeny are reported to be inferior bloomers.

Native habitat

Hypericum frondosum is native to the south-central United States, from North Carolina west to Kentucky, and south from Georgia to Texas.

 
 
FacebookTwitterRSS Feed

Stay in touch!

 

Sign up for twice-monthly eNews, plus notification of new posts:

 

* indicates required