Brugmansia: Growing in a frost-prone UK
Brugmansia, or Datura as it used to be known, can be grown almost anywhere. However in areas susceptible to frost these vigorous plants do not reach the dimensions they can achieve when permanently planted out in warmer areas. With the right growing conditions some of the most spectacular container plants imaginable can be grown year after year.
Commonly known as Angel Trumpets, Brugmansia are from high altitude, moist tropical cloud forests with specific temperature and humidity. These conditions vary between species but generally speaking a warm day at about 23°C combined with a high humidity will keep them happy. If night temperatures are around 10°C, give or take 3°C, a strong growth rate will ensue. In summer months these temperatures can be easily exceeded, but an average humidity of 70% will ensure optimal growth and full flower colour. The good news is, the UK has the perfect humidity and temperature to support brugmansia growth, but the more challenging part is overwintering the plant when temperatures dip below freezing. To understand how this may affect different species let’s get back to basics.
There are seven Brugmansia species. These species are then divided into two natural genetically isolated groups, cold growing (CG) and warm growing (WG).
Cold growing Brugmansia include B.Sanguinea, B.Vulcanicola, B.Arborea and all cultivated hybrid varieties of these are adapted to the cool climate of their native habitat in the Andes, South America.
B.Sanguinea is native to the midland and lowland areas around the Andes mountain range. It grows wildly throughout Bolivia, Chile, Columbia, Ecuador, and Peru. It has also been found growing at sea level in Chile. They are endemic to the Andes Mountains from Colombia to northern Chile at elevations from 2,000 to 3,000 m and it is not uncommon for them to receive light frosts.
B.Vulcanicola is found in Columbia in regions of high altitude and even there only isolated plants are found. The B.Vulcanicola is considered to be difficult to grow in hot climates preferring higher altitudes with cooler climates.
B.Arborea is native to the Andes Mountains of southern Colombia, Ecuador, Peru, western Bolivia, and northern Chile. As the hardiest of all Brugmansia species in regards to both cold and drought, they are often found in the drier valleys of the Andes, in areas with an annual rainfall of 400 to 1,400 mm. Occurring at elevations of 2000 to 3000 m. It is not uncommon for them to receive light frosts.
These cold growing species tend to flower in the UK autumn time, when temperatures fall to the level they prefer. In some mild winters they will flower under protection through winter. The one species which is slightly different is B.Arborea, which can sometimes grow better in warm periods as it has a higher heat tolerance.
Warm growing species include.B.Suaveolens, B.Insignis, B.Versicolor, B.Aurea, and hybrid cultivated varieties of these, which all grow well in a UK summer. Each species has slightly different growing conditions.
B. Suaveolens is originally endemic to the coastal rainforests of south-east Brazil, where it grows below 1,000 m (3,300 ft) along river banks and forest edges with warm temperatures, high humidity, and heavy rainfall.
B. insignis is predominantly found in gardens in the Andean foothills of western Amazonia where it is an important plant in indigenous medicine and rituals.
B.versicolor is found in the Northwestern Amazonian rainforest, primarily in Ecuador and northern Peru.
B. Aurea is native to the highland areas around the Andes mountain range in South America.
All warm growing species originate from high humidity warm regions but frosts are unlikely due to the shelter of the rainforest, cloud forest and altitude. In their native habitat these warm growing species require a lot of water and we recommend frequently watering during the hot summer months and regularly feeding to encourage flowers.
It is important to know the microclimate of your garden balancing humidity with sun, wind and shade. Best conditions for warm growing Brugmansia species generally tend to be part shade in summer to stop the root ball drying out and over scorching the leaves or flowers. An enclosed area of your garden with some shade facing south or west will suit best, protecting them from strong winds and hot sunny days.
The image below is a heat tolerance chart relating to different Brugmansia species. Notably B.Insignis is the most tender and difficult to grow in the UK but other species have a better tolerance levels. For reference, Candida is a two species Brugmansia of B.Versicolor and B.Aurea. For more information on two species and three species Brugmansia see this blog link:
In the UK during prolonged cold conditions it is necessary to force a Brugmansia into dormancy for the winter, during cold frosts and snow. This is easily achievable by lightly fleecing and storing them in a dry storage room, garage, shed or greenhouse which is frost free and ventilated. The foliage can be removed but this may drop by itself which is perfectly fine. Growth will recommence again when temperatures exceed 8 to 10C.
If you would like to purchase a Brugmansia from Exotic Earth Plants we hold a growing collection, which we have been cultivating since 2016. We are exhibiting at several plant fairs over the summer of 2019. Please see www.exoticearthplants.co.uk for more information.