Tropical luxuriance with temperate ease
BY C. COLSTON BURRELL
Tropical plants lend an air of the exotic to temperate gardens, but planting them out each spring and lifting them every fall can be a lot of work.
If these chores don’t appeal to you, but tropicalismo does, try planting hardy aralias. Whether small in stature or gigantic, aralias add the bold texture you crave, minus the fuss.
The genus Aralia contains some 30 species, found throughout North America and Asia, though scarcely a dozen are grown ornamentally. Herbaceous plants as well as shrubs and small trees comprise this diverse group. The kinship is apparent in their spherical clusters of small-petaled, white, green, or yellow flowers and their dramatic, deeply lobed or compound leaves.
THE SMALLER HERBACEOUS SPECIES
Wild sarsaparilla (A. nudicaulis; hardy to USDA Zones 3-8) takes its name from its similarity to true sarsaparilla (Smilax officinalis), a Mexican native whose pungent roots were used to flavor soft drinks, ice cream, and candy. Wild sarsaparilla forms open colonies from spreading roots. Each leaf consists of a whorl of three pinnately compound segments atop a slender stalk one to one and a half feet tall. The leaves are shiny and tinged with bronze as they emerge, but fade to green when fully expanded. The golf-ball-size spherical flower clusters are also arranged in a triad. Small, yellowish flowers open in late spring or early summer, followed by blue-black berries. The foliage makes an attractive, often open groundcover, alone or in combination with ferns, grasses, and late-blooming plants such as asters and goldenrods. Sarsaparilla excels as a mass planting under shrubs and trees, especially in deep shade where other plants seldom thrive. Plant sarsaparilla in average to rich, moist soil in light to full shade. Established plants tolerate dry soil with ease.
LARGE HERBACEOUS SPECIES
My favorite aralias are found among the large herbaceous species. These understated aristocrats rise heads above their smaller cousin. Their charm comes not from gaudy flowers but from sheer girth. Though most of these large species seem little more than variations on a theme, there are discernible differences in the shape and carriage of the leaflets and in the size and spacing of the flower clusters.
Placing American spikenard (A. racemosa; Zones 3-8) at the top of the heap betrays my bias toward natives. This denizen of both deciduous and dense coniferous woodlands from the Rockies to the East Coast has a commanding presence. Though totally herbaceous, mature plants grow four to six feet tall on thick, nearly black stems, and are often mistaken for shrubs. The enormous, tropical-looking leaves are layered in overlapping tiers, and may reach three feet or more in length, with up to 27 heart-shaped leaflets. In early to midsummer, numerous small spherical clusters of up to 20 pale green flowers are collected into dense terminal clusters one to three feet long. In late summer, fleshy berries turn deep purple. The berries are an attractive addition to the garden as long as they last, but are quickly devoured by birds.
In the dense conifer forests of northern California and southern Oregon, elk clover (A. californica; Zones 4-8) replaces spikenard. I first encountered this comely species jutting out of a rock outcropping, bathed in mist from a tumbling mountain stream. The medium green leaflets are oval rather than heart-shaped, sparsely toothed, and are carried flat. Densely clustered umbels of up to 70 white flowers, followed by deep purple berries, droop attractively from the ends of the four- to six-foot stems. Though rated by references as hardy only to Zone 6, the plant thrived in my Zone 4 Minnesota garden until I tried to move it. Though I thought I took ample care, the fleshy taproot disagreed, and the plant promptly died. The moral of this sad tale is, dig deep—aralias have massive roots that may run three feet or more from the crown of the plant.
Japanese spikenard (A. cordata; Zones 4-8) is similar to our native species but more open in form, with leaves held upward at an angle. The broad, blunt-tipped, heart-shaped leaflets are held horizontally on the intricate infrastructure of the compound leaves. Erect to drooping flower clusters top each of the five-foot canes well above the leaves of this multistemmed species. The Korean species A. continentalis is also similar, but open and delicate when contrasted with the other species. The creamy flowers, borne in drooping clusters, fade to pink, and the purple berries are carried on pink-tinted pedicels, adding subtly to the autumn display.
Himalayan spikenard (A. cachemirica; Zones 4-8) garners the blue ribbon for the most elegant and gargantuan herbaceous aralia species. The stout stems four to 10 feet tall are crowned by elongated inflorescences sporting well-spaced spherical flower clusters that resemble gumballs. I love their eccentric look and their chartreuse flower color. The huge compound leaves, easily four feet long, have delicate, regularly spaced leaflets that lend an ordered air to the foliage. The autumn berry display on a full-grown clump is spectacular.
THE WOODY SPECIES
Alarming is the first word that springs to mind when describing the shrubby aralias, quickly followed by curious, elegant, and dramatic. The stems are clothed in stiff, menacing spines that have engendered such names as prickly ash, Hercules’-club, and my favorite, devil’s walking stick. The tripinnate leaves share a similar construction to the herbaceous species, though the leaflets are much smaller, usually two to three inches across, and less filmy. The spines move right up the stems and onto the girders of the four- to six-foot leaves, so care is called for when hobnobbing with these plants. Our native Hercules’-club (A. spinosa; Zones 4-9) rises to 25 feet or more, and forms large colonies from fast-spreading underground stems. Huge spherical to domed clusters of tiny round white flowers are followed by a dramatic display of purple-black berries. Despite its stunning beauty, this species is seldom employed in ornamental settings, though it excels in naturalistic settings along the edges of woodlands or as a focal point at the back of a pond, and makes a formidable barrier if you wish to exclude or confine someone or something. Birds relish the purple-black fruits.
Japanese angelica (A. elata; Zones 4-9) shares many traits with its American counterpart. The sparsely branched stems produce huge leaves artfully displayed in flat tiers. Purple-black berries hang in drooping clusters in autumn from stems up to 20 feet tall. The variegated selections of this species are deified by hortaholics and command a dear price even when small. They are beautiful in full foliage, as well as in winter, when the knobby stems resemble reindeer antlers. ‘Variegata’ is a stunning large shrub with regular white edging to the leaflets. ‘Silver Umbrella’ is a European selection with finer-textured, white-edged leaves. ‘Aureovariegata’ boasts yellow variegation fading to cream rather than pure white. These slow-growing, well-behaved selections still have spines, but the single, low-branching stems reach only 8 to 15 feet when mature. Variegated selections are grafted onto our native species, so remove the sometimes plentiful root suckers. In its wild form, this species is reportedly hardy to Zone 3, though the variegated selections perform best in Zone 5 and warmer. It should be noted that this species is invasive in some parts of the country.
Designing with Aralias
Mature aralias are huge and are best used as accents or specimens. Place these architectural gems where the sun can illuminate them from behind, revealing the intricacies of their structure. A backdrop of dense evergreens also shows them off to great advantage. Herbaceous species are late emerging in the spring, so surround the decorative, peonylike shoots with a colorful carpet of snowdrops, scillas, anemones, and other bulbs. For summer companions, choose bold male fern (Dryopteris filix-mas). golden hostas, toad lilies (Tricyrtis spp.), and carpet-forming wild gingers and epimediums. Add more tropical texture to the summer garden with lush ferns such as interrupted fern (Osmunda claytoniana), ostrich fern (Matteuccia struthiopteris), and Goldie’s fern (Dryopteris goldiana).
Woody aralias make formidable hedges and are great for wildlife plantings. Use variegated Japanese aralia in containers or in ground as a specimen or dramatic focal point where the horizontal tiers of variegated foliage add a spot of light and drama on a terrace or at the end of a walkway.—C.C.B.
When you grow the large aralias, you go all the way. These goliaths are not for the timid or indecisive gardener. Pick a spot and live with it, as established plants need a back hoe to move them because of their massive, succulent taproots. Plant herbaceous aralias in humus-rich, moist neutral or acidic soil in partial to deep shade. Plants grow well in the dense, season-long shade of mature evergreens. The woody species will grow in full sun, but variegated selections may burn in the hot sun of high summer. Set out young plants in their permanent spot. If planting more than one specimen, leave at least four feet between the plants to allow for their mature spread.
Propagate aralias from root cuttings taken in spring or fall, or sow ripe seed indoors after four weeks of cold, moist stratification, or outdoors in the fall. Plants grow quickly but take several years to reach mature size. Self-sown seedlings may appear, and I am carefully watching the nonnative species to head off any potential problems with invasiveness.
Whether woody or herbaceous, persistent or fleeting, aralias are sure to enliven the summer garden with their floral and foliage displays. So try an aralia or two. Once you discover the beauty of tropical luxuriance with temperate ease, you may find yourself replacing a few cannas and bananas. H
For sources of aralias, turn to page 79.