The Lesser-Known Hardy Ericaceous Shrubs, Part 2: Ledum to ZenobiaBy Todd Boland (Todd_Boland)
February 11, 2012
(Editor's Note: This article was originally published on January 24, 2009. Your comments are welcome, but pleae be aware that authors of previously published articles may not be able to respond to your questions.)
In part two of this two part series on the lesser known ericaceous shrubs, I will discuss those genera from Ledum to Zenobia. As a reminder, this group generally requires organic-rich, moist, yet well drained soil that has an acidic pH. Dappled shade seems to be the best lighting conditions but there are a couple of exceptions. Many of these are broad-leaved evergreens so can provide year-round interest in the garden landscape. Florally, they have 5 fused petals which make the flowers appear bell-shaped, saucer shaped or urn-shaped.
Labrador-tea, Ledum groenlandicum and L. palustre, are now classified as a Rhododendron. However, this species is quite distinct so I will include it here. Not readily available in the trade, this evergreen is super hardy, to zone 1. They prefer full sun and evenly moist soil. They dislike hot, dry summers so are only suitable for cooler summer regions. New leaves emerge covered in a dense coating of white hairs. As the leaves mature, the upper surface becomes dark green and rugose while the lower surface retains hairs that turn cinnamon. Winter foliage is bronzy. In late spring-early summer, plants produce terminal heads of bright white, starry flowers. This plant will reach about 1 m. The foliage is very aromatic and dried leaves were used extensively as a source of tea during the American War of Independence.
Details of Ledum groenlandicum
Sand myrtle, Leiophyllum buxifolium, is native to the eastern US from New Jersey south to Florida. This species is grown primarily as a rock garden subject since they reach just 20 cm. The evergreen leaves are small, narrow and glossy, often turning bronzy in winter. Tiny clusters of pale pink, star-like flowers are prolifically produced from late spring into early summer. Sandy, peaty soil in sun to part shade is best. They are rated for zone 5.
Flower details of Leiophyllum buxifolium
Leucothoe fontanesiana or hobblebush, is native to the mountains of SE USA. This broad-leaved evergreen has elliptical to lance-shaped leaves on bushes that reach about 1.5 m. New foliage often emerges red (similar to Japanese Andromeda or Pieris) and winter foliage often turns purplish. In spring, plants produce axillary drooping clusters of white, urn-shaped flowers. This species is rated for zone 5. There are several named selections including ‘Scarletta' with exceptional red new foliage, ‘Rainbow' whose leaves are irregularly streaked in yellow, cream and pink and ‘Nana', a dwarf selection that grows to about 30 cm. Other noteworthy species to consider are L. axillaris, L. davisiae, L. catesbaei, L. racemosa and L. recurva, all North American natives hardy to zone 6. Dappled shade seems to suit them best.
Leucothoe fontanesiana 'Nana' showing spring growth, flowers and winter colour
To the left are the flowers of L. davisiae while on the right are the foliage and flowers of L. fontanesiana 'Rainbow'
Loiseleuria procumbens or alpine azalea, is an Arctic-affinity plant which extends as far south as the White Mountain of New Hampshire. Plants are completely prostrate with tiny, dark green summer leaves that turn purplish in winter. Minute pink, star-like flowers are produced in late spring. This delicate and charming member of the ericaceous family is unfortunately, very difficult to grow although some alpine growers in the UK have been successful. They require a cool, moist position with very sharp drainage. They are rated for zone 1.
Details of Loiseleuria procumbens
Lyonia is a genus very closely related to Leucothoe and in fact, some Lyonia have been classified as Leucothoe in the past. Most of the species are not hardy beyond zone 7 but L. ligustrina, called maleberry, can survive into zone 6. This species will reach 1 m or a little higher at the northern end of its range, which extends from Maine to Florida. The leaves are veiny and leathery. Upright, axillary clusters of white, urn-shaped flowers are produced in late spring. At least a half day of sun is required to maximize flower production. Leaves adopt red tones in winter.
Winter colour on Lyonia ligustrina
From southern Chile and Argentina comes Pernettya mucronata, considered Gaultheria mucronata by some authorities. This evergreen has tiny, spiny leaves not unlike a miniature holly. Plants may reach 1.5 m. Their small white, urn-shaped flowers develop into large berries which range in colour from white through pink, red and purple. There are many named cultivars, based on their fruit colour. A few of the more common are ‘Mulberry Wine' (dark purple), ‘Snow White' (white), ‘Rosalind' (carmine-pink), ‘Crimsonia' (red) and ‘Stag River' (compact, hardiest selection with pink fruit). The fruit often last through the entire winter. Full sun produces the bushiest, most fruitful plants.
Details of Pernettya mucronata 'Stagg River'
Kalmiopsis leachiana is a beautiful species found exclusively in Oregon. It is not reliably hardy beyond zone 7. However, a hybrid between it and Phyllodoce breweri, called X Phylliopsis hillieri, can look similar but is hardy to zone 5. The growth form is low (to 25 cm) and dense with heath-like growth. The terminal spikes of flowers are pink with semi-open, saucer-shaped blooms. This hybrid prefers full sun and is more tolerant to heat than most ericaceous plants. There are several named selections, all worth growing in the rockery or among a heath/heather garden. These selections include ‘Coppelia', ‘Pinocchio', ‘Sprite' and ‘Sugar Plum'.
Flowers from X Phylliopsis hillieri 'Pinocchio' and 'Sugar Plum'
There are hundreds of species of Vaccinium and even more hybrids and named selections. Many are suitable for zone 5 or 6. Many of these are grown primarily for their fruit. Rather than get into specifics, I will simply recommend both the highbush blueberry (V. corymbosum) and low sweet blueberry (V. angustifolium) for their spectacular scarlet fall foliage.
The fall colour of Vaccinium angustifolium
The last ericaceous shrub of note is Zenobia pulverulenta. This 1-2 m tall shrub is native to the coastal pine barrens of eastern USA. Their leaves are deciduous in the northern part of its range to semi-evergreen in the south. The main claim to fame are its blue-green foliage and rather prolific display of relatively large, axillary, bell-shaped white flowers in early summer. The flowers are also sweetly fragrant of anise, adding to this plants attraction. In fall, the leaves take on yellow to reddish tones. They are hardy to zone 5 and very tolerant to heat and humidity as long as the soil remains reasonably moist. 'Woodlander's Blue' has particularly good blue-green coloured foliage.
A young plant of Zenobia pulverulenta 'Woodlander's Blue'
So as you can see, in zone 6 and colder, there are a host of ericaceous, acid-loving shrubs that can be incorporated with your rhododendrons, heaths and heathers, to provide a wide diversity of plant forms, textures and flowers. Since many are evergreen and have leaves that turn bronzy, reddish or purple-tinted in cold weather, they can provide needed garden interest in the dull days of winter.
I would like to thank the following people for the use of their pictures: baccharis (Lyonia ligustrina), darius (Leucothoe 'Rainbow') and mgarr (Zenobia pulverulenta).