Bright, brash berries put Gaultheria in a class of its own during winter. The shrubby evergreen plants stand out in borders, mixed beds and containers in the coldest months, with their clusters of striking berries in a wide range of colours set against dark, often spiky, foliage. Gaultheria's main use is for winter interest but the genus also shines in early summer with a flourish of delicate bell-shaped flowers that identify it as part of Ericaceae, the heather family.
Like Rhododendron, Pieris and others ericaceous plants, Gaultheria is lime-hating and requires an acidic soil, rich in humus and free-draining in order to thrive. Any potential planting site needs to have acidic qualities if the plants are to survive. Acidifying soil is difficult and expensive. Ericaceous compost can be added to open soil but it will leach away over time. It is best to avoid growing Gaultheria and other ericaceous plants on alkaline soil.
There are as many as 180 species within the genus, though fewer than a third of these are in commercial production. The online RHS Plantfinder holds 69 recorded species and cultivars but shows many are no longer supplied. The easiest-to-find cultivars include G. procumbens and G. shallon, which are widely used in beds and containers. The addition of Pernettya mucronata into the genus (now G. mucronata) increases the range. Most Gaultheria plants are dioecious but many G. mucronata cultivars are self-fertile and are now perhaps the main focus for breeding efforts within the genus. When planting other varieties, at least one male plant will be required to ensure pollination and resulting berries.
The need for an acid soil does not rule Gaultheria out of projects in alkaline areas. With many cultivars around 50cm in height, the plants make great additions to winter container displays alongside other winter-interest plants including Calluna, Erica, Acorus, Hedera, Crocus, Viola and Helichrysum italicum.
When used in beds and borders, Gaultheria does not like to be crowded. Over time, many Gaultheria species will spread indefinitely via suckering action, making it a good low-level ground-cover option. A planting distance of around 45cm is suitable for most species. It sits well alongside other small, lime-hating plants in the border. Larger species such as G. yunnanensis require more space and are best used as stand-alone specimen plants or in clusters of three.
Plants in the genus do not perform well if allowed to dry out. A layer of mulch is recommended after planting to keep moisture in the soil and suppress competition from weeds. They can prove delicate in colder areas in exposed locations and will benefit from shelter from extreme conditions.
WHAT THE SPECIALISTS SAY
Alistair Scott, proprietor, Kirkdale Nurseries, Aberdeenshire "Pernettya species now come under the Gaultheria heading, bringing an advantage over other species within the genus as they are self-fertile. Most Gaultheria plants have either male or female flowers and both are needed if you are to get a good display of berries.
"However, G. mucronata 'Bell's Seedling' Award of Garden Merit (AGM), is self-fertile and will also act to pollinate other Gaultheria cultivars. If a dioecious variety such as G. shallon is being used, you will need at least one male plant to ensure a good berry display from the females. Some Gaultheria plants, including G. procumbens AGM, can be a little delicate and the Pernettya forms often make a hardier choice. They make great ground-cover plants and are best used in mass plantings. They love acidic soils and ericaceous compost or soils will be needed to get the best performance out of them."
Joan Lorraine, National Plant Collection holder, Greencombe Garden Trust, Somerset "We have about 20 varieties in the collection. The larger Chinese types such as G. yunnanensis are very good performers and make very dramatic plants. I am still waiting to find out how large they grow but the collection is turning into a selection of large, dramatic plants, having given them the space to thrive.
"The very best form, in my opinion, is G. fragrantissima. It gives wonderful blue berries in the autumn. Once established, it requires little upkeep but should never be forgotten. It doesn't take kindly to severe weather extremes and should never be allowed to dry out."
Anthony Henn, director, Gardens for Life, Hertfordshire "I used to work in retail and it was a very popular genus back in the 1970s and 1980s. A good volume still gets sold, but not to us - it is an acid-loving genus and the majority of our work is done on neutral and alkaline soils. We do use it occasionally as a front for a mixed border, where it comes into its own during winter with a good show of stunning berries.
"Ericaceous compost needs to be added to condition the soil if it's not already acidic, but this will drain away over time. If the soil you are working with is not suitable, Gaultheria is best used in containers and works well for potted winter displays and hanging baskets. It's a great plant and I would use it more if our work was centred in an area with acid soils.
"It can be quite an expensive plant to use for large ground cover and is quite slow growing. If the budget is there, that's not a problem. We tend to use it in groups of three when put into borders.
"G. procumbens AGM is the main variety we use. There have been some interesting introductions in the past couple of years. G. procumbens AGM is such a good performer, you don't need anything better. It has glossy leaves and pinky flowers."
SPECIES AND CULTIVARS
G. adenothrix is a useful ground-cover plant for semi-shade.
G. cuneata 'Cuneate Wintergreen' Award of Garden Merit (AGM) is a dwarf, spreading, densely branched evergreen shrub with small, oval, leathery, mid-green leaves, racemes of white, bell-shaped flowers in late spring and white spherical fruit in autumn.
G. cuneata 'Pinkie' is similar but bears vibrant pink fruit.
G. fragrantissima is not very hardy in Britain, only performing well outdoors in the milder areas of the country, growing well in Cornwall. The bruised leaves have a powerful camphor-like scent and flowers are scented like lily of the valley.
G. humifusa is an ideal option for alpine planting. The stems are less than 20cm in length and have small oval-shaped leaves, which are 1-2cm long. It bears solitary, bell-shaped flowers with white to light pink corollas and golden anthers. The fruit is a bright to dull red.
G. itoana is a small, creeping, Taiwanese shrub with attractive, glossy, dark green leaves and white summer berries that are loved by insects. It grows to 50cm x 25cm and is a good alpine option.
G. mucronata, formerly Pernettya mucronata, produces a mass of edible, though flavourless, lilac-coloured berries on female plants, which require male plants for pollination.
G. mucronata 'Bell's Seedling' AGM (f/m) is a hermaphrodite form with clusters of small white flowers in late spring and early summer followed in autumn by dark crimson berries.
G. mucronata 'Crimsonia' AGM (f) has white flowers followed by large crimson fruits in autumn.
G. mucronata 'Lilacina' (f) has lilac-rose berries.
G. mucronata 'Lilian' (f) offers white flowers followed in autumn by pink berries.
G. mucronata 'Male Boxberry' is a compact, evergreen, suckering shrub that has small, spiny-tipped, dark green, glossy leaves and white, nodding, urn-shaped flowers in spring. This male form will ensure that female plants produce a good crop of autumn berries.
G. mucronata 'Mulberry Wine' AGM (f) is similar to 'Wintertime' but produces magenta-purple fruits, which deepen in colour with age.
G. mucronata 'Signaal' (f) is a compact, bushy, suckering evergreen shrub with glossy, dark green leaves, white flowers and scarlet berries. It is female and has a height and spread of 1.2m.
G. mucronata 'Wintertime' AGM (f) is a small, thicket-forming evergreen shrub with spiny-tipped, dark green leaves. It has clusters of small white flowers in late spring or early summer, followed in autumn by white berries.
G. ovatifolia is a small, low shrub reaching 35cm in height. It has small, solitary, bell-shaped flowers in shades of white to very light pink with reddish bracts in spring, leading to red fruits.
G. procumbens AGM is a dwarf, spreading shrub with rounded, evergreen foliage that takes on red tinges in winter. Pale pink or white flowers appear in summer and are followed by bright red berries.
G. procumbens 'Very Berry' is a great container option with profuse fruits in winter.
G. pumila is an extremely small species growing to just 8cm high in clumping mounds of branches laden with small, green, oval leaves. It will produce oversized 5cm rosy pink fleshy berries.
G. shallon is a large, evergreen shrub with leathery, ovate, mid-green leaves tipped with a bristle tooth. It has reddish stems and racemes of nodding, bell-shaped, pinkish-white flowers in summer, followed by aromatic, dark purple, edible berries in autumn.
G. wisleyensis 'Pink Pixie' is a hardy variety reaching 40cm in height. It has white flowers in May, which are followed by pink fruit in late autumn.