A Gardening Journal

The Best Season Ever: 'Palmgold' Chinese Plumbago

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Unique among plumbagos, the leaves of 'Palmgold' emerge pale yellow, and mute only moderately during the Summer. Slender burgundy stems provide plenty of contrast in themselves; the sky-blue flowers that appear late Summer into Fall are either a bonus or, for purists, a distraction from the more sophisticated and season-long interplay of the leaves and stems.

 

Spring into Summer, Ceratostigma willmottianum 'Palmgold' is "just" a foliage plant. In the picture below, the shrub is receiving only partial sun. The foliage is as bright as if the sun were full, but the stems are much paler: milky pink at best. 

 

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In full sun, the stems darken to honest burgundy. The five-petaled blue flowers—dead ringers in size and coloring for those of phlox, despite its being a member of an altogether unrelated botanical family—are almost a step too far. Besides bringing to the party a third color, blue, they hog our attention just by being flowers. Yes, they are blue (a color that's always in short supply) and, yes, they appear in late Summer (when flowers of any color can become scarce).

 

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But most plumbago flowers are blue, whereas only this one cultivar has leaves anything other than green. Better, then, to keep the focus on what's really fantastic about 'Palmgold': Foliage, not flowers.

 

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I'm keeping at least one shrub of 'Palmgold' in a pot; the plant isn't reliably hardy below Zone 7, although it's worth the effort to succeed with it in Zone 6. (See "Quirks," below.) By late Summer, the pairing of the gold foliage and burgundy stems finally suggested two worthy partners in the picture above: the tub of purple-leaved rice, a thrilling and easy aquatic annual; and the potted lemon bush, a eucalyptus cousin with shockingly fragrant leaves and—more to the point of any association with 'Palmgold'—slender stems that are also dusty burgundy.

 

Here's how to grow this uniquely colorful plumbago:

 

Latin Name

Ceratostigma willmottianum 'Palmgold'; also sold as 'My Love' and 'Desert Skies'

Common Name

Palmgold Chinese plumbago

Family

Plumbaginaceae, the Plumbago family.

What kind of plant is it?

Deciduous shrub.

Hardiness

Zones 7 - 10, possibly into Zone 6 with exceptional drainage and careful handling. See "Quirks and special cases." 

Habit

Multi-stemmed, self-branching, and clumping. Woodier than C. plumbaginoides, and without the latter's propensity to spread stoloniferously.  

Rate of Growth

Medium to fast.

Size in ten years

Size is dependent on culture and climate. Individuals growing in-ground in full sun and in a frost-free climate, or when planted permanently in a conservatory bed, will grow faster and larger than those in containers, or growing in-ground in less congenial circumstances. Ultimately, two feet tall and three to four feet wide; wider if stems are layered so that the bush can spread. 

Texture

Dense and leafy enough that 'Palmgold' can function as groundcover where hardy. See "Culture," both "How to handle it" boxes, and "Quirks and special cases" for tactics.

Grown for

its foliage, which is colorful throughout its Spring-to-Fall season: Emerging leaves are even brighter than mature ones; in full sun the portion flanking the central vein is nearly white. Mature leaves are pure gold, softening only slightly to chartreuse as they become shaded by newer growth. Unlike foliage of the straight species, that of 'Palmgold' isn't an early adopter of Fall coloring: Instead of turning to a (beautiful) burgundy, the leaves remain gold as the blue flowers emerge in late Summer and Fall. The muted burgundy of the bark of the new stems is a terrific contrast, but not so showy that you'd grow 'Palmgold' specifically for the stems. 

 

its flowers: Pale blue, and the size and form of those of phlox, the blossoms of 'Palmgold' are highlighted by the surrounding gold foliage. Each petal has a faint pink-burgundy vein that nicely echoes the shrub's burgundy stems.

 

its season-long show: 'Palmgold' is handsome and lively from the moment new foliage emerges in Spring to Fall's hard frosts, which halt the flowering as well as encouraging the shedding of the leaves for the Winter.

Flowering season

Unusually late. Flowers appear at the tips of new growth, which needs several months to become mature enough for their production. In milder climates with correspondingly longer growing seasons, flowering might begin in July or August. Here in southern New England, flowers aren't likely to appear before September. 

Color combinations

Because 'Palmgold' is, at once, colorful (as in, brightly colored) as well as full of colors (as in, "Wow, there's a lot going on there"), the plant has a surprising level of aesthetic self-sufficiency. The coloristic and textural interplay of the gold foliage with the burgundy stems is, in itself, so satisfying that the addition of the blue flowers is almost an overload. It's a mistake, then, to think of each of this shrub's colors as an invitation to explore further into that particular shade's "affinity group." Just because indigo goes with sky blue, and sky-blue goes with yellow and burgundy, it doesn't follow that all four of them all go together. The same is true for chrome yellow and saturated burgundy.

 

Instead, it's the very congeniality of the diverse colors of 'Palmgold' (gold, soft burgundy, and sky blue) that precludes addition of other colors. Other than neutral green, then, don't look further. 

Plant partners

Take advantage of the surprising lack of flexibility in the yellow-burgundy-blue palette of 'Palmgold' to explore how wildly neighboring plants can flaunt their differences in texture, habit, type, and overall size. The more diligently you hew to the hues, so to speak, the farther afield you can romp with everything else. 

 

When growing 'Palmgold' in-ground where it's reliably hardy, the first choice will probably be to use it as a mound of brightness amid neighbors that are darker, such as Aeonium arboreum 'Zwartkop'. Because the leaves of 'Palmgold' are fairly even in their gold tones, it's possible to choose neighboring plants with variegated foliage as long as they incorporate only colors from the 'Palmgold' palette. See my mention of Yucca and Phormium, below.     

 

If you have the opportunity in terms of climate, available space, and your own style, consider using 'Palmgold' as a large-scale underplanting for taller plants with a small footprint. What about surrounding an informal grove of narrow verticals, such as Ilex crenata 'Sky Pencil' or Cupressus sempervirens 'Stricta' with as large a sweep of 'Palmgold' as you can muster? A grid or a line-up of coniferous or broadleaf standards? Or eruptions of spiky-leaved choices of Yucca or Phormium? Both of these latter offer many options for foliage that is striped with at least one of the "permitted" 'Palmgold' colors. Phormium brings the additional option of cultivars whose leaves are solidly tinted just the right shade of dusty burgundy.   

 

When attempting to grow 'Palmgold' in-ground where it's not reliably hardy (see "Quirks and special cases," below), siting it a foot or so back from the edge of a raised bed is a help, as is providing all possible sun and heat in what, for the Ceratostigma, is going to be experienced as a chillier climate with weaker sun. Neighboring plants to the east, south, and west of the clump of 'Palmgold' should be shorter, so as not to reduce sun-fall on 'Palmgold' itself. I'm going to try pairing 'Palmgold' with the shrubby forms of Euphorbia, which can be had with burgundy or variegated leaves in addition to their yellow flowers. Maybe I'll try both 'Nothowlee' (purple leaves and yellow flowers) and 'Ascot Rainbow' (yellow-variegated leaves), with some prickly-pear cacti at the front and a clump of Crocosmia 'Solfaterre' at the side: Its bronze foliage and yellow flowers would fit right in.

 

When including 'Palmgold' in a mixed container planting just for the warm months, the sky's the limit: The assemblage is temporary, and there's no need to restrict the soil to the lean and well-drained stuff needed to maximize Winter hardiness. What about this combination of high drama among foliage shapes and coloring, plus some added pale-yellow flowers: 'Palmgold', a rooted cutting of Ficus carica, Hibiscus acetosella, Bulbine frutescens, and Lantana 'Chapel Hill Yellow'?

 

'Palmgold' that's grown year-round as a containered specimen can be relocated to take advantage of the seasonal peaks of your horticulture as well as your inspiration. In the pictures above, I didn't think of putting my pots of 'Palmgold', purple-leaved rice, and lemon bush next to one another until August. Earlier that season, I had moved my 'Palmgold' container near my 'Color Guard' yucca, to take advantage of its bright and yellow-striped sword leaves. Then, warming to all three themes—yellow, stripes, and swords—I moved it nearer my pot of 'Yellow Stripe' Dianella. Another Summer, the pot of 'Palmgold' found itself amid a group of yellow-flowered crown-of-thorns.

Where to use it in your garden

'Palmgold' can grace your garden many ways. In-ground, use it as a colorful accent at the front of a bed or, planted en masse, as a striking groundcover. It tolerates part shade (although foliage color may mute), so can groundcover beneath and at the front of taller leggy neighbors.

 

This hardy plumbago is even slower to break dormancy than is usual for a family of plants notable for snoozing well into Spring; this delay makes all forms of Ceratostigma excellent companions for interplanted Spring bulbs. 

 

'Palmgold' grows fairly fast, and also flowers on first-year growth. On both counts, then, it succeeds when used as an annual, as colorful filler in a mixed container just for the warm months. 'Palmgold' is also worth growing year-round as I do, as a solo specimen in its own container.

 

See "Plant partners," above, for suggestions for including 'Palmgold' in such diverse contexts.

Culture

Best in sun. When growing in-ground with the hope of establishing the shrub for the long term, good drainage in Winter is essential, even if it is achieved at the expense of a reduced proportion of organic matter. In contrast, when used as part of a container planting intended only for the warm months, rich moist soil produces the lushest growth. When grown in a container year-round, soil can also be rich and moisture retentive as long as it is allowed to become drier during the plant's cool-season dormancy. 

How to handle it: The Basics.

Plant in Spring. As is typical for hardy plumbagos, 'Palmgold' is naturally bushy, so it isn't necessary to pinch soft growth for additional stems and flowers the way you'd do for, say, salvias or asters. Through the warm months, allow to grow and flower ab libitum. In milder climates—Zone 8 and warmer—you could cut all stems back to an inch or two in Fall, but in Zone 7 and colder, wait to do this until Spring. If interplanted with Winter- or Spring-flowering bulbs, cut 'Palmgold' back before the quickly-emerging growth of the bulbs makes access awkward. 

How to handle: Another option—or two!

'Palmgold' is easy in a container. The shrub is so hard working that it's worth growing it as large as possible. If grown as a solo, in a container that is brought into shelter as needed for Winter survival, grow in rich soil. Spring through Fall, water to keep the soil reasonably moist; if needed, repot in a larger container in Spring or early Summer to ease the watering needed to keep a pot-bound 'Palmgold' actively growing. Bring into shelter in Fall; if you wait until the plant experiences mild frosts, you'll be less likely to bring bugs into shelter, too. Reduce watering so that the soil dries out somewhat between waterings. Increase watering when new foliage begins to emerge in late Winter. If (lucky you) your 'Palmgold' is as large as you could ever want, this is the time to cut back all stems by half, or even more. Otherwise, just let the shrub grow freely. Place outside after danger of frost is past; water and fertilize generously to encourage maximal growth.

 

'Palmgold' grows quickly enough that it can be used as a component of a mixed warm-weather container. (See "Plant partners," above.) Plant the container in Spring, with rich soil and "Soil Moist" granules, which will help encourage lush growth as well as less-frequent watering. Ceratostigma growth is self-branching, so there's no need to pinch it to encourage bushiness. Plant right at the front of the container, where 'Palmgold' can spill over the edge with its typical grace, and also enjoy the most sun.

Quirks and special cases

'Palmgold' is so useful when growing in-ground that it's worth trying to establish it in climates somewhat colder than Zone 7. As usual when attempting to expand a plant's range into a colder climate, protecting 'Palmgold' from excess water is even more important than protection from cold. Incorporate as many of the tactics below as you can.

 

Plant on a slope, no matter how slight, so that surface water is more likely to pass on by rather than soak in.

 

Planting in a raised bed always helps drainage—as long as you don't plant 'Palmgold' right at the edge. Cold penetrates into beds that are at ground-level only from above, but can also penetrate into the soil of a raised bed from the sides. A raised bed for 'Palmgold', then, is probably more effective if this horizontal penetration is minimized by raising the bed only a couple of inches above its surroundings. The height of a raised bed intended for species that are otherwise quite hardy but succumb to Winter only because of excess moisture—cacti, say—can be as lofty as you want. 

 

Reduce the amount of organic matter in the soil, which will also reduce the soil's ability to retain water; it's usually easiest to do this by mixing in plenty of builder's sand or small gravel.

 

Plant (in Spring) more deeply than usual, so that there are below-ground portions of stems from which the shrub can resprout even if killed back to the ground.

 

After the weather has become cold enough for the shrub to have dropped its leaves—to have, in other words, become fully dormant—bury the base of the shrub under three or four inches of chunky dry mulch. (This is the time and place to use that bag of clunky mulch nuggets that you bought by mistake.) If you don't mind the look, then lay a sheet of cardboard over the shrub, bending down its flexible exposed branches in the process. Crease the cardboard at the high point, as if you were creating the roof of a split-level house. Anchor the cardboard by placing atop it a few bricks, stones, heavy branches, or (what I do) logs from the Winter's stack of split firewood. The cardboard will prevent Winter precipitation from reaching the shrub, and will also reduce or even eliminate wind chill.

 

Remove the cardboard "roof" when Spring is in the air; scuffle back the mulch a couple of weeks later. Wait until you see signs of emerging new foliage to cut back any stems.  

Downsides

If only 'Palmgold' were a zone or two hardier—and less attractive to browsers.

Variants

The flowers of Ceratostigma willmottianium 'Forest Blue', also known as 'Lice', would seem to be somewhat darker—although I couldn't find a nursery description that came right out and said so. The foliage is typical for the species: green becoming burgundy as flowers emerge.

 

Ceratostigma griffithii is shorter—to about 15"—but with flowers, habit, hardiness, and foliage that are similar to those of the straight species of C. willmottianum. The flowers of C. griffithii 'Snow Flurries' are white. In contrast to the reduced size and vigor that can sometimes typify white-flowered forms of otherwise-colorful plants, this one is reported to be a fast-moving giant, maturing to three feet tall and eight feet across in a year. Even in a hot climate that would facilitate such prodigious growth, flowering doesn't begin until late October.

 

C. plumbaginoides is the hardiest and hardest-working of the hardy plumbagos. When provided with good drainage, it can survive climates as cold as Zone 5. This is probably because its slender stems originate deeply underground, which also ensures that this stoloniferous species can spread indefinitely. The clear-blue flowers emerge in late Summer (sometimes as early as mid-August for me, but always by September), just when the green leaves enter their strikingly long season of burgundy Fall coloring.

Availability

On-line as well as at retailers.

Propagation

By semi-ripe cuttings—i.e., those taken in late Summer, where the tip of the cutting is soft new growth, but the base has already hardened—and by layering.    

Native habitat

Ceratostigma willmottianum is native to western China and Tibet. 'Palmgold' was bred at the Palmstead Nursery in the United Kingdom.

 
 
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