Four thousand different species make the Erica family the 14th largest plant group in the world. The shrubs and low trees of Ericaceae species and genera originate from mainly continental countries. They are all acid-loving plants so any added fertiliser or compost has to be lime-free. Most have a fine-hair root system and do not have prominent taproots. They need good free-draining soil, so when placing them in the clay-based soils be cautious positioning them. Growing them on banks and inclines can help but they do have fine roots so will suffer if the area is summer dry. Mulching around the roots will help keep root runs moist. Plant families are recognised by the flower shape, and all Ericaceae, be it a large rhododendron tree or a small heather bush, have in common the bell–shaped or tubular flower.
These trees with beautiful winter flowers also have many herbal medicinal properties. While some are toxic to the human body, others offer pain relief from neuralgia and joint pain. The medicinal varieties are all species (original) of Ericaceae. Plant breeders enjoy the challenge of working with rhododendrons probably because they are such magnificent, eye-catching trees. There are now in excess of 10,000 registered cultivars. Many genera originate in China and the Himalayan areas. Subtropical varieties come from equatorial places like Hawaii.
These have sometimes been labelled ‘dwarf rhododendrons’ as they have many similarities to their larger cousins. Suited to smaller gardens, they fill any deeply shaded areas of the garden as underplanting and put on a great spring show. They too have been targeted by enthusiastic propagators and many cultivars now exist. Like rhododendrons, there are varieties that have wonderful perfume.
North American Ericaceae
With the many species of mammals that live in the vast American continent, the variety of plants is equally diverse. Plants have evolved here to produce fruit and berries. These attract browsing animals so the ingested fruit is carried away and expressed back onto the ground neatly packaged in a pile of nourishing manure. In the Ericaceae group there is a large collection of herbs that supports the abundant animal kingdom. The group contains herbs that the original settlers used in many ways. The berries were harvested in summer and autumn, dried and stored away for medicinal use when needed. Contained in small packages they were part of the medicine bag that Indian women carried with them.
This is an important herb group. Wintergreen oil from Gaultheria procumbens has many applications. It became popular with early European settlers to America as the oil has high levels of methyl salicylate and, like acetylsalicylic acid (aspirin), it is soothing for acute muscular pain. Many commercial pain-killing body rubs still contain this herb. It is also used in toothpaste flavouring. Unfortunately I have never been able to source Gaultheria procumbens herb plants in New Zealand. It would grow well in the South Island where the temperatures are high in summer and cool in winter. I do grow Gaultheria shallon, known also as shallon or salal, which is a low-spreading evergreen. Manawatu’s climate is too warm for it to flower and set seed though. This is reputed to have similar properties to wintergreen.
Kalmia, Leucothe, Pieris
These are all familiar ornamental plants in New Zealand. They grow slowly and not more than 2.5m here in Manawatu. All very showy, they are not considered herbs but with wonderful perfumes they must have some aromatherapy applications. Calico bush (kalmia) has always been a personal favourite. In winter time with few flowers in the herb garden the air is fragrant with the sweetness of the bush. The flowers are good for picking and their attractive cluster of pink or white flowers have eye appeal. There are red-flowering cultivars available which have speckles and patterning on the petals. With the typical leathery leafed foliage, these shrubs are hardy doers and like cool root runs in shady areas.
Bearberry is, like its cousins the Vacciniums, a low ground cover creeping herb. Arctostaphylos uva–ursi is well known for controlling urinary infections and, as its name suggests, the berries are ‘icecream’ to bears.
Huckleberry is the common name for cranberry (Vaccinium myrtillus), perhaps the most well known of the cranberry family. There are more than 450 species in this group. Vaccinium oxycoccos is the European cranberry. Many are bog plants and need conditions similar to New Zealand’s West Coast to thrive. Areas with drought-prone summers will not suit these herbs. Vaccinium macrocarpum and Vaccinium vitis-idaea (cowberry) are available in NZ from time to time and survive well in damp, shady areas. The other member of this group are the blueberries. A North American friend remarked that he was not sure of the origin of the blueberries commercially available here. The ones he remembers in his native Washington were fully deciduous. Perhaps the cultivars here originate from Vaccinium myrsinites which has the common name of evergreen blueberry. When purchasing blueberries, find out the ones more tolerant of your local growing conditions. There are differences and the recommendations for North and South Island varieties should be stated on the labels. If not, ask.
Calluna is the botanical name for heather. Calluna vulgaris (the common variety) is a native of Europe and is the low, tiny leafed shrub that thrives on poor heath and bog terrain. So much so in wasteland areas of NZ it has been declared a plant pest. The proliferation of this herb along the Desert Road of the mid North Island is causing concern. As it is used medicinally in similar ways to wintergreen, maybe there is a potential industry here as the Conservation Department is sure to allow free harvesting for some entrepreneur. Another consideration is to set up bee hives in the area as heather flowers produce delicious honey.
And last but not least are the heaths that all belong to the Erica group. There are many different species and cultivars now available from garden centres and their brilliant show of all-over colour in late winter and spring add cheer to the landscape. Be cautious of having lime anywhere near these garden shrubs as they are acid-lovers. Fortunately NZ soil tends to the acid side. Many heaths prefer sun so plant them in the rockery. They do not respond to being crowded out by other plants and suffer dieback and fungal problems if touching their neighbours.
Some other members of Ericaceae include:
Arbutus, Enkianthus, Epigaeas, Gaulnettya, Leather Leaf, Leduma, Manzanita, Menziesia, Pernettya, Sorrel Tree, Tree Heath, Zenoba.
HerbNews – Spring 2012