Ericas and callunas (heaths and heathers)
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Heaths (Erica) and heathers (Calluna) are superb garden plants. They are suitable for a wide range of uses and generally require little maintenance. Many have very attractive and unusual flowers, but they are not only grown for their flowers. Some have brightly coloured winter foliage or vivid new spring growth and others are superb ground covers or rockery plants that would be well worth growing even if they never flowered.
The two genera are closely related and often look very similar with tiny narrow leaves and small bell-shaped flowers. The hardy species also have similar environmental preferences and, in the wild, they often grow in close proximity. However, there are some important differences between and within the genera that have a considerable influence on their cultivation.
Erica is a genus of around 800 species but there is only one heather species: Calluna vulgaris. However, there are so many heather cultivars that at first it is hard to believe they are all derived from just one species, but they are. They are still a fairly variable lot as regards size and foliage, although they are all hardy to at least -20°C.
There are three main groups of ericas. The northern European species that come from cold winter areas, such as Britain, northern France and Scandinavia; the southern European/North African from the Iberian peninsular and the Algeria/Tunisia region; and the South African ericas, which are mainly from the Cape region with a few species found as far north as Zimbabwe.
The northern European species are all very hardy and tend to be ground covers or small shrubs. Those from southern Europe often grow into large shrubs and may be somewhat frost tender where frosts occur regularly. The South African ericas range from tiny rounded bushes to large shrubs; some are hardy to around -8°C, but most are damaged if regularly exposed to temperatures below -4°C. They do very well in mild coastal gardens.
Which heaths and heathers will grow best in your garden depends on the climate and soil conditions. In mild areas the taller, tender Erica species are often used to provide winter flower colour. In very cold winter areas the hardy heaths and heathers are used as ground covers and their spring and autumn flowers are a common sight. Ericas from drier regions will tolerate some drought a fairly wide range of soil conditions, but callunas prefer moist, acid soil.
Selection and cultivation
Most heaths and heathers have all the features that you would expect of desirable garden plants. They are compact, colourful, flower well, and generally tolerant of wind and coastal conditions. However, of the thousands planted each year, many are quickly removed because they fail to perform as the gardeners expected. This is no fault of the plants and is generally due to unrealistic expectations or a lack of experience on the part of the gardeners. Heaths and heathers are not difficult to grow, provided you choose the right plants and follow a few cultivation rules.
Flowers, foliage and growth habit
Undoubtedly, the South African ericas have the most spectacular flowers. They tend to be tubular or globe-shaped and may be very brightly coloured, as in the orange-red Erica cerinthoides, or very delicately shaded in pastel shades, such as the soft pink of Erica parkeri. South African ericas vary in their flowering season, so by planting a selection of species it is possible to have flowers through most of the year.
The flowers of European ericas are very small when compared to most of the South African species, but they often make up for this with an abundance of bloom. Their tiny bell-shaped flowers are generally white or shades of pink and a plant in full bloom may be absolutely smothered. They tend to bloom in autumn or spring and a few flower in winter.
Most callunas have flowers that are similar to those of European ericas, but a few cultivars, such as 'Alba Plena' and 'H.E. Beale', have double flowers, which make them appear to be very heavy blooming. The heathers mainly bloom in the late summer and autumn.
South African ericas usually have deep green foliage that shows little variation over the course of the year. European ericas and callunas, however, are available in a wide range of foliage colours including deep green, yellow, gold tinted red, and silver-grey. Many also intensify in colour in winter or have bright yellow or red new spring growth.
Heaths and heathers vary enormously in size. Most northern European ericas and callunas are small, not more than about 40 cm × 60 cm, but some of the southern European species are up to 4 m high. South African ericas range from about 40 cm × 40 cm to over 2 m high.
There are heaths and heather for all sizes and styles of gardens. Which you choose depends on the climatic conditions, available space and the intended use.
Soil requirements
All the plants of the erica family (Erica, Calluna, Rhododendron, Pieris, Kalmia, etc.) have very fine, hair like, roots. These roots determine their soil requirements: fine roots cannot penetrate heavy soil, they rapidly rot in wet soils and desiccate quickly in dry soil. They are not able to grow to any great depth but may form a dense mat and cover a large area.
In the wild, ericaceous plants generally grow in three main environments: woodland with a soil composed of high-humus leaf mould; moist peat based soils; or in moist alpine pockets of fairly new, gritty, mineral based soils. All of these soils tend to be rather low in nutrients, moist, well aerated, and are mildly to quite highly acidic. Ericas and callunas prefer soil in the range pH5-6, although a few are moderately lime tolerant.
Where many gardeners run into difficulties is in assuming that all plants with tiny needle-like leaves are drought tolerant. Heaths and heathers need regular summer moisture. Some may be able to withstand short periods of drought but in the main their root structure limits their drought tolerance. Moisture is important, but good drainage is also vital. Prolonged periods in wet soil will inevitably lead to the drowning of the roots or root rot.
Heaths and heathers have relatively low nutrient requirements but they will benefit from additional feeding. However, avoid concentrated chemical fertilisers because there's always a temptation to add just a little bit more and that may cause severe, even fatal, damage to the very fine roots. Mild fertilisers, such as liquid blood and bone or slow release pellets, are safe and just as effective.
None of these requirements are difficult to meet and they do not require the soil to be extensively modified. Erica roots do not go below about 50 cm so it is really only a matter of ensuring that the sub-soil drains well and providing added humus in the topsoil. This is nothing more than you would do for any broad-leafed plant, but because ericas and callunas look like they should thrive in hot, dry conditions, that is what they are often subjected to and that is where the trouble starts.
Pruning and cut flower use
Ericas are not very long lived plants. Most are past their best by about ten years old, they may struggle on for many more years but they tend to become unsightly. However, careful pruning can prolong their useful life. Trim them back by about a third to a half, depending on size, after flowering. Sometimes the smaller mound-forming plants die out in the centre. A light annual trimming will help to prevent this. Hard cutting back will sometimes rejuvenate old plants, but replacement is usually the best option.
Many ericas and a few calluna cultivars, especially 'H.E. Beale', make excellent cut flowers. Stems picked as the first buds are opening will continue to develop and may last two weeks in water. The winter flowering ericas are often grown with cut flower use in mind, but any erica or calluna may be used in floral work; simply cut the stems as required. Such trimming back will often benefit the bush by making it more dense and compact.
Container growing
Ericas and callunas are best grown in gardens but where they can't be grown outdoors, the tender ericas make excellent container plants for patios or greenhouses. They were all the rage among wealthy gardeners when first introduced into Europe in the late 18th and early 19th centuries and special greenhouses were built for growing South African ericas and other plants of the Cape.
Use the same acid potting mix that you would for potted azaleas, rhododendrons or camellias. A 10 litre pot is large enough for most ericas and should ensure adequate nutrients for the first year or so.
Ericas tend to fill a pot with a such a solid mass of fine roots that it can be difficult for water to penetrate if applied to the soil surface. Water by soaking the pot in a sink or bath for several minutes or until the soil surface becomes moist. Let the excess water drain before placing the pot back on its saucer. Add liquid fertiliser to the water to combat the leaching that occurs when the excess water is drained off.
Pests and diseases
Grown in the appropriate conditions heaths and heathers are remarkably free of pests and diseases. Scale insects or red spider mites occasionally cause damage, but their presence is generally an indication that the conditions are too hot and dry.
The only significant disease is phytophthora root rot, which is usually the result of poorly drained soil. Some fungicides will control it but the disease is not usually noticed until too late.
Propagation
Erica and callunas are usually propagated from tiny summer and autumn tip cuttings taken non-flowering stems or by removing self-layered pieces. They also respond well to dropping, which is a form of layering. In winter or early spring, prune the stock plant to encourage new growth. Prepare an area of soil nearby by adding leaf mould or peat so that it is loose and airy. Lift the plant and bury it, angled on its side with just the leaf tips exposed, in the specially prepared soil. By the following winter the plant will have produced numerous layers, which may be removed and grown on.
The species may be raised from their seed, which is very fine. Collect the seed by shaking dried seed heads over an envelope or paper bag. The seed usually germinates best on fine sphagnum moss or peat-based potting mix. It should not be covered with soil but the seed tray should have a glass cover and be kept in the shade at around 15–22°C.
Callunas
All callunas are derived from Calluna vulgaris, the only species of this genus. They thrive over most of the country, but are usually at their best where the seasons are very distinct and the summers are not too humid. The following are just a few of several hundred cultivars.
'Alba Plena'
Bright green foliage. White double flowers. 30 cm × 45 cm.
'Alportii'
Deep green foliage. Dark reddish pink flowers. 60 cm × 75 cm.
'Andrew Proudley'
Yellow foliage that develops orange and bronze tones from mid autumn. Purplish-pink flowers. 15 cm × 40 cm.
'Aurea'
Bright yellow new growth that turns to bronze in winter. Light purplish-pink flowers. 25 cm × 40 cm.
'Cuprea'
Bright green summer foliage bronze in winter and yellowish green new growth. Light pink flowers. 30 cm × 50 cm.
'David Eason'
Mid green foliage. Bright pink flowers. 20 cm × 60 cm.
'Elsie Purnell'
Light green foliage tinted silver. Mid-pink double flowers with light centres. 40 cm × 50 cm.
'Foxhollow Wanderer'
Deep green foliage. Deep lavender pink flowers. Spreading growth habit. 15 cm × 70 cm.
'Foxii Nana'
Bright green foliage turning bronze in winter. Lavender flowers but seldom blooms. Grown for its very dense compact habit. 10 cm × 25 cm.
'Goldsworth Crimson'
Deep green foliage. Pinkish red flowers. 60 cm × 75 cm.
'H.E. Beale'
Bright green foliage. Bright pink double flowers on long stems (excellent cut flowers). 60 cm × 80 cm.
'J.H. Hamilton'
Bright green foliage. Soft pink double flowers. 25 cm × 40 cm.
'Mrs Ronald Gray'
Dark green foliage. Reddish-purple flowers. 10 cm × 40 cm.
'Robert Chapman'
Greenish-yellow foliage that turns to orange then red as the weather cools in autumn. Bright lavender-pink flowers. 25 cm × 50 cm.
'Sister Anne'
Silver-grey foliage turning bronze in winter. Bright, light pink flowers. 20 cm × 40 cm.
'Tib'
Deep green foliage. Reddish-purple double flowers. 20 cm × 45 cm.
'Wickwar Flame'
Golden foliage that develops bright orange tones from mid autumn. Mid pink flowers. 30 cm × 50 cm.
Ericas
Species
The following are some of the more common or influential species. They are divided into three groups: those that are tender and prefer near frost-free conditions, those that are moderately hardy and capable of tolerating regular light frosts, and those that are very hardy and should be capable of surviving very winters.
Tender
Erica conica (South African)
Mid green foliage with clusters of 8 mm long widely flared, deep pink flowers in spring. 60 cm × 60 cm.
Erica glauca (South African)
Fine bluish-green foliage and unusual pendulous pink and cream flowers with overlapping scale-like petals. This species flowers in winter and early spring. 60 cm × 60 cm.
Erica parkeri (South African)
Bright green foliage with clusters of 20 mm long, pale pink, tubular flowers in winter and spring. 1.2 m × 75 cm.
Erica patersonia (South African)
Soft bright green foliage and yellow tubular flowers up to 20 mm long in late winter and spring. 1 m × 60 cm.
Erica peziza (South African)
Light to mid green foliage and massed small white flowers in winter and spring. It is often used as a cut flower. 90 cm × 75 cm.
Erica regia (South African)
Bright green foliage and clusters of short tubular flowers in spring. The flowers are white at the base changing abruptly to bright red at the tips. This is a very striking shrub. 90 cm × 75 cm.
Erica sessiliflora (South African)
Dark green foliage and terminal clusters of light yellowish-green 20 mm long tubular flowers in late winter or spring. 80 cm × 60 cm. Hardy to -5°C.
Erica ventricosa (South African)
Fine, almost furry, mid to deep green foliage. In spring it produces massed clusters of pale to mid pink, upward facing bell shaped flowers with flared mouths. 50 cm × 50 cm.
Erica walkeri (South African)
Bright green foliage and, in spring, massed bright mid pink short tubular flowers with widely flared mouths. 60 cm × 60 cm.
Moderately hardy
Erica arborea (European)
Light green foliage and masses of tiny whitish grey flowers in spring. 1.8 m × 1 m.
Erica australis (European)
Deep green foliage with massed tiny mauve to purplish-red flowers in spring. A white form is also available. 1.5 m × 1.2 m.
Erica bauera (South African)
Greyish to mid green foliage and clustered 20 mm long tubular white flowers tinted pink in late winter and spring. 1.2 m × 60 cm.
Erica canaliculata (South African)
Bright green foliage with massed deep pinkish purple open bell-shaped flowers in winter. It makes a good cut flower. 2 m × 1.5 m.
Erica cerinthoides (South African)
Dark green foliage with clusters of vivid orange-red, slightly hairy, 30 mm long, tubular flowers in late winter, spring and summer. 1 m × 1.2 m.
Erica cruenta (South African)
Bright green foliage and vivid red, 25 mm long, narrow tubular flowers. They appear mainly in spring but this plant may flower at any time. 1.2 m × 80 cm.
Erica mammosa (South African)
Bright green foliage and massed bright red 20 mm long tubular flowers in spring. 75 cm × 50 cm.
Erica melanthera (South African)
Bright green foliage and masses of pinkish purple flowers in winter. It is widely grown as a cut flower. 1 m × 1.2 m. Hardy to -10°C.
Erica verticillata (South African)
Mid green foliage and deep pink 20 mm long tubular flowers. These appear throughout the year but usually most heavily in early summer. 1.6 m × 1 m.
Erica wilmorei (South African)
Soft mid green foliage with large clusters of 20 mm long white tipped, deep pink tubular flowers in winter. A hose-in-hose or double form is also available. 1 m × 60 cm.
Very hardy
Erica carnea (European)
Deep green foliage and tiny pale pink flowers in winter and spring. 35 cm × 50 cm.
Erica ciliaris (European)
Light green foliage and small deep-reddish purple flowers in late summer and autumn. 20 cm × 75 cm.
Erica cinerea (European)
The foliage colour of this species varies from light greyish green to deep bronze-green. Grey and gold foliage forms also occur. The flowers, which appear in late summer and autumn, are usually pale pink but they may be white to deep purplish-pink. 35 cm × 75 cm.
Erica erigena (European)
Deep green foliage and bright pink flowers in winter and spring. 50 cm × 75 cm.
Erica tetralix (European)
This species has greyish-green foliage, but the best forms are quite silvery. Light pink or white flowers, that are large for a European erica, appear in summer and autumn. 20 cm × 45 cm.
Erica vagans (European)
Deep green foliage and pale pink flowers in clusters in summer and autumn. White forms are also available. 60 cm × 80 cm.
Cultivars
Very few cultivars or selected forms of South African ericas are available, so all of these listed here are derived from hardy European species unless otherwise noted.
'Aurea'
Bright yellow foliage with orange tints in winter and deep pink flowers from mid winter. 20 cm × 40 cm.
'Candy'
A form of Erica cerinthoides, a South African erica, with light pink, flushed deep pink, 30 mm long tubular flowers. Apart from the different colour of the flowers it is identical to the species. Although of South African origin, it is hardy to -10°C with some damage.
'C.D. Eason'
Deep green foliage and massed deep pink flowers in summer. 25 cm × 45 cm.
'Darley Dale'
This is a cross between Erica carnea and Erica erigena that has given rise to many hybrids. The original cross, known as Erica × darleyensis, has deep green foliage and pale lilac flowers from late autumn to mid spring. 35 cm × 45 cm.
'Dawn'
Bright green foliage with yellowish new growth and deep pink flowers in autumn. 20 cm × 50 cm.
'Golden Drop'
Bright yellow summer foliage turning to bronze in winter with purplish-pink flowers in winter and spring. 20 cm × 1 m.
'Gwavas'
Light green foliage with yellowish winter buds and new growth. The pale pink flowers appear in winter and spring. 40 cm × 75 cm.
'Jack H. Brummage'
Bright yellow summer foliage that takes on gold to orange tones in winter. Deep pink flowers appear in autumn and winter. 30 cm × 40 cm.
'Irish Lemon'
Deep green foliage with bright yellow new growth and pinkish-purple flowers in summer and autumn. 20 cm × 40 cm.
'Irish Salmon'
Light coloured foliage, with new growth tinted red and small, bright clear pink flowers in late winter and early spring. 40 cm × 50 cm.
'Mrs D.F. Maxwell'
Bright mid green foliage with pink flowers from late summer to early winter. 20 cm × 60 cm.
'Rosslare'
Dark green foliage and bright pink flowers from mid winter, peaking in early spring. 50 cm × 50 cm.
'Silver Beads' ('Silberschmelze')
Deep green foliage and white flowers in autumn and winter. 45 cm × 50 cm.
'Springwood Pink' and 'Springwood White'
Deep green foliage and, in late winter and spring, bright light pink or white flowers. These two cultivars are superb when massed as large scale ground covers. 25 cm × 60 cm.
'W.T. Rackliff'
Deep green foliage with lighter coloured new growth and white flowers. It blooms mainly in the spring with occasional flowers from autumn through winter. 30 cm × 40 cm.
'Valerie Proudley'
Light green foliage with bright golden-yellow new growth and white flowers in summer and autumn. 20 cm × 60 cm.
'Vivellii'
Dark green foliage tinted red in winter and bright carmine flowers in late winter and spring. 30 cm × 50 cm.
Copyright Geoff Bryant
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