JARS v46n3 - Heathers as Companion Plants

Heathers as Companion Plants
Alice Knight
Elma, Washington

Rewards are great when rhododendrons share their beds with heather "cousins". There won't be any new "hybrids", but you can enjoy heathers in bloom every day of the year!
Heathers (a common term which includes both heaths and heathers) are really excellent companion plants for rhododendrons and azaleas. Most like the same acid soil, respond to rhododendron-type fertilizers and can provide yearlong foliage interest and flower beauty.
The heathers are actually comprised of nearly 30 species plus several other closely related members of the Ericaceae family. Four genera are usually grouped as heather: Calluna , Daboecia , Bruckenthalia and Erica (also known as heath).
Other small-leaved plants resembling heathers are sometimes improperly dubbed "heather". Also, beware of the beautifully blooming "heathers" often in stores at Christmas or in early spring. These are the South African ericas, also known as "Cape heaths", which must be moved inside or treated as annuals any place the temperature dips below 28°Fahrenheit.

The Heather Species
Caliuna vulgaris is the Scottish heather or ling of England and has been collected over much of western Europe from the cold Scandinavian northlands to the warm Mediterranean area. It is the only "true heather". Other species are technically heaths but commonly called heather.
Daboecia includes D. cantabrica , the Irish heath, Daboecia azorica , a related plant from the Azores, and hybrids of the two. Daboecias originally came from the coastal areas of Portugal, Spain, France and Ireland.
Bruckenthalia spiculifolia , the Balkan heather or spike heath, originated in the mountains of Romania and the Balkan peninsula and south in the mountains of northern Turkey and Greece. Bruckenthalia is one of the few heathers which begin flowering in May. It also has a pleasing anise fragrance.
About two dozen species of Erica , (heaths) complete the heather group. All these versatile ericaceous "cousins" easily make themselves at home in almost any garden. Cultivars can range from spreading mats to tree heaths which tower to 20 feet or more. Flower colors range from white through shades of pink, purple and red to almost black. Foliage colors include many shades of green, gray, gold to bronze and even red! New growth on some cultivars often changes with the season.
It is important to select cultivars carefully when adding heathers to any garden. Some cultivars tolerate adverse weather conditions much better than others. Some must have full sun to grow and flower well. Other cultivars can tolerate shady spots or moist areas, and some do not like "wet feet."
Blooming time and height and shape of the plant also should be considered. Flower colors and foliage usually blend well but should be taken into consideration when heathers become companion plants.
Even though full sun is usually best, most heathers also do well in partial or filtered shade or in an area which gets sun at least part of the day. Heathers should not be planted directly under trees or shrubs but can be planted in areas which receive only a few hours of good light.

The Calluna Cultivars
Callunas are all summer flowering evergreen shrubs with small scale-like leaves. Growth habits vary from low spreading ground huggers to upright bushes almost three feet tall. Flowers range from white through pink, lavender and purple to crimson in both single and double flowering forms. The smooth leaved foliage often has shades of green, silver, gold and bronze, some with pink or white tips and some changing colors with the season.
Personal favorites as companion plants are some of the low bushy cultivars which can easily be maintained. 'County Wicklow' is an attractive bush with bright green foliage and double shell pink flowers from July through August. 'Kinlochruel' is its white-flowering sport. 'Foxii Nana' and 'Nana Compacta' are two excellent dwarf pincushion types of Calluna with mauve and lavender flowers. Both are very compact, seldom need pruning and are attractive all year.
'Mrs. Ronald Gray' and 'White Lawn' are good groundcover varieties which can also be planted in rockeries or where they can cascade over a wall. If you'd like to add foliage interest, consider some of the compact golden-foliaged callunas which have deep bronze or red tips in winter. 'Multicolor' and 'Sir John Charrington' sport golden foliage in summer which turns to bronze and copper in winter. 'Minima' is a dwarf variety with medium green to bronze foliage 'Silver Knight' has pale lavender flowers in August and September and attractive silvery-gray foliage all year.
Callunas are probably the most hardy of all heathers, and some cultivars can survive very severe winters. Taller growing cultivars are good for cut flowers or dried arrangements. Taller growing cultivars must be pruned annually because flower buds do not set on old wood. This causes untrimmed plants to become quite unattractive.

The Daboecia Cultivars
Daboecia cultivars do not look much like heather. They have small, flat leaves which are shiny on top and whitish underneath. These Irish bell heathers are natural bog plants and can tolerate "wet feet." Stems are fairly long and tapering. Flowers form along the top portion of the stem and are egg-shaped, sometimes as long as half an inch.
Daboecia 'William Buchanan' is an excellent lower growing cultivar with attractive crimson flowers from June through October. 'Alba' is upright to about 20 inches and has attractive light green foliage with white blossoms from June through October.

The Heaths
We rely on heath, the Erica species, for winter flowering plants; however, this is the group which can, with thoughtful selection, provide something in bloom every day of the year! Erica carnea is the winter heath. Its natural habitat is the mountainous area of Central Europe, and plants thrive well under a blanket of snow with flowers emerging as the snow melts. Flower buds form in the summer, but it takes up to nine months for some carneas to finish flowering.
Established plants require very little attention and, when properly planted, form a close carpet which smothers weeds. Most varieties of Erica carnea are compact in habit and fast growing, making excellent plants for rock gardens, slopes or drifts of color. Leaves are fine and narrow and range from golden or pale green to deep or grayish green, some with streaks of yellow. New tip growth is often pink or creamy. Flowers are bell-shaped with downward trend and are tightly clustered on each stem. Most are hardy to U.S.D.A. Zone 4, especially with the protection of snow cover.
Flowering of Erica carnea varies with cultivars, beginning as early as November with some lasting through May. Colors range from white through pink to deep rose pink and reddish-purple.
Some choice spreading Erica carnea cultivars are 'Springwood Pink' and 'Springwood White', 'Pink Spangles', 'Foxhollow Fairy' and 'Loughrigg'. Good bushier compact cultivars include 'Vivellii' and 'Porter's Red', both of which have deep rose pink to reddish purple flowers between January and May.
Erica x darleyensis includes many hybrids of Erica erigena and Erica carnea . This group is a little less hardy than Erica carnea ; however, plants have the reputation of blooming twice a year. Most cultivars set buds in June, and many begin flowering in September and continue flowering through May!
Pink and white flowering types of Erica x darleyensis are often improperly labeled as 'Med' or 'Mediterranean Pink' or 'Mediterranean White', rather than 'Darley Dale' and 'Alba' (or 'Silberschmelze').
A personal favorite is Erica x darleyensis 'Furzey' which has dark green foliage that takes on a pinkish cast in May and deep lilac pink flowers from October into May. 'Furzey' and 'Alba' are often used here in the Pacific Northwest for all-winter color in commercial landscaping where planters or beds feature bright-blooming annuals during the summer. Erica x darleyensis cultivars are good looking all year and need very little, if any, pruning. When plants outgrow their area and pruning is necessary, it is important to prune when flowers fade, or just before, because buds are set in June for the next season's flowers. Late pruning results in sparse flowers.
Two spreading cultivars are Erica x darleyensis 'Jenny Porter', a very pale lilac, and 'Margaret Porter', a deeper lilac. 'Jack H. Brummage' is a golden-foliaged cultivar with orange and deeper gold accents setting off sometimes sparse heliotrope flowers.
Erica cinerea is a fine leaved, late spring and summer blooming plant with an unusually wide range of flower colors. Most varieties are nicely shaped bushes from 6-18 inches tall. Plants can suffer foliage damage when temperatures near 0°Fahrenheit, however, often recover with hard pruning in spring. Flower colors range from white through many shades of pink and lavender to magenta and a very dark purplish crimson. Some are even bicolor.
Erica cinerea 'C. D. Eason', a showy magenta, begins flowering in early June and continues into September. 'Purple Beauty' is a low spreading variety with rich purple flowers from June into October. 'Apple Blossom" is a delicate shell pink and 'Velvet Night' blossoms are almost black!
Erica tetralix cultivars offer a combination of gray foliage with long lasting blossoms between June and October. This species originated in Northern Europe, often growing in bogs from Finland to Poland and throughout Britain. It is tolerant of a wide variety of climates and soil conditions. Flowers range from white through shades of pink to a deep magenta in 'Con Underwood'. Plants keep a neat bushy habit and are usually between 6-12 inches tall.
The Cornish heath, Erica vagans , is another long flowering, summer blooming plant with good symmetrical growth which makes it useful as a hedge or border plant. Stems are stiff and upright. Bell-shaped flowers bloom from July into October in colors from white through purple. Faded flowers become russet brown and cling to the stem in winter. To encourage flowering and tidiness, plants should be pruned back to the base of the flower shoot in early spring.
Very reliable cultivars of Erica vagans include 'Mrs. D. F. Maxwell', a deep rose pink, 'St. Kaveme', a lighter pink, and 'Lyonesse', a white flowering variety.
Other summer blooming ericas such as Erica ciliaris (Dorset heath), Erica umbellata , Erica x stuartii , Erica x watsonii and Erica x williamsii are also useful companion plants but may be harder to find in most nurseries. Several other ericas are commonly grouped as tree heaths. These can be useful as background plants or as focal plants in areas where winters are not too cold. Once established, many tree heathers are quite hardy but they can be damaged by heavy snowfall or cold winter winds.
Erica arborea 'Alpina' is a graceful beauty with a profusion of fragrant white flowers in March and April. 'Estrella Gold' is a golden foliaged form.
Erica terminalis is a Corsican heath and the only tree heath which flowers druing the summer months.
When adding heathers as companion plants, it is wise to think ahead. Take into consideration growing habit, flowering time and soil and light requirements. Don't plant a small dwarf calluna next to a vigorously spreading Erica carnea or crowd a tree heath into an area less than five or six feet square. Most heather labels give cultivar name, color of flower, blooming time, growth habit and average height at maturity - usually about five years.
Heathers can be easily maintained with annual pruning. Some Erica carnea , Erica x darleyensis and dwarf Calluna vulgaris cultivars do not need regular pruning unless they are outgrowing their space. Heathers should be pruned in early fall or early spring before new growth begins and buds for the next flowering season are set. Avoid late fall pruning in areas where moisture can collect and freeze in the stems, causing stem splitting.
Heathers are tolerant of a wide range of soil, but some species do have different pH preferences. Calluna vulgaris , Daboecia azorica , Doboecia x scotica , Erica ciliaris , Erica cinerea , Erica tetralix , Erica x watsonii and Erica x williamsii usually do best in acid soil.
Species tolerant of some lime include: Daboecia cantabrica and many Erica species such as E. arborea , E. australis , Erica carnea , E. x darleyensis , E. erigena , E. lusitanica and E. terminalis . Erica vagans does well in neutral soil.
Soil can usually be amended to adjust pH and improve drainage. Sand, vermiculite or perlite will improve drainage. Adding moist peat moss around the roots at planting time is often a good idea.
Early spring or early fall are usually best planting times, although in many parts of the world container-grown plants can be set out almost anytime. Once established, heathers are very easy-care plants. It is important to keep new plants well watered until they become established. Heathers are shallow-rooted, and allowing them to dry out is reason for most new plant losses.
Some people claim that heathers should not be fertilized; however, we believe that all plants need a boost now and then! Treat your heaths and heathers to a little ferilizer when you feed your rhododendrons. Keep the fertilizer off the foliage. Apply away from the main stem near the plant's drip line and water in to prevent foliage burn.
Established, well tended heather plants are relatively free from both pests and diseases. Most problems are usually cultural. Burrowing animals sometimes cause damage by undermining roots which can then dry out. Heathers do not seem to be a favorite food for most wild life, but both rabbits and deer will occasionally do a pruning job for you. Bigger culprits are dogs and cats (usually the neighbor's!) who often claim a heather as a bed or bathroom! Heathers are tough little guys, and they make excellent companion plants for rhododendrons.

Alice Knight, a former journalist, and her husband Bob operate Heather Acres, a heather specialty nursery in Elma, Wash. Both are founding members of the North American Heather Society and the recently formed chapter, the Cascade Heather Society. Alice Knight spoke to members of the ARS at the ARS Western Regional Conference in Olympia, Wash., in 1991.