The genus camellias comprises about 300 species as well as countless varieties and hybrids. They all belong to the tea leaf family (Theaceae). The Chinese camellia (Camellia sinensis) is a thousand-year-old cultivated plant in East Asia – for over 4,000 years, green tea and fermented black tea have been extracted from its leaves. In addition to the tea plant itself, there are other camellias that are extremely popular as ornamental shrubs because of their beautiful large flowers. The most famous camellia species is the Japanese camellia (Camellia japonica). It was discovered in 1735 by the Swedish plant researcher Carl von Linné and named after Georg Joseph Kamel, a Moravian-Austrian Jesuit priest and naturalist who described the plant world of the Philippines for the first time.
The first camellias probably arrived in Europe in the 16th century – curiously enough mainly due to the efforts of the European states to import the precious tea plants. In China the optically very similar ornamental camellias were often declared as tea camellias because the country wanted to protect its monopoly in tea cultivation at that time. As a result, camellia was already a very popular garden plant in England in the middle of the 18th century, but tea was still sourced from East Asia.
Appearance and growth
Camellia has evergreen, alternate, mostly elliptic leaves with dark green upper and light green undersides. The flowers bear striking yellow stamens in the centre. They remind a little of the flowers of peonies and can reach a diameter of up to 15 centimetres depending on the variety. In autumn the camellia produces seeds in the form of capsule fruits. The loosely growing, mostly upright shrubs grow up to four metres high in mild regions of the garden. At their natural sites there are camellias up to 11 metres high and over 1,000 years old.
Location and substrate
In the open, camellias are classic solitary shrubs. They grow best in shady areas, even under larger trees, as long as they do not have intolerant roots. They can be combined with rhododendrons, carpet dogwoods and other woody plants and shrubs that have similar soil requirements. Due to their origin, they are also well suited as solitary shrubs for Japanese gardens. The plants feel at home in the tub on sunny terraces and balconies. But they also grow well in unheated conservatories.
From spring to winter, camellias stand optimally in a pot in a wind-protected, semi-shade place on the terrace. In summer they can also tolerate a little more sun with a good water supply. A good exposure is the prerequisite for the camellias to create many new flower buds.
Commercially available rhododendron soil is suitable as a substrate as it contains hardly any lime and has a correspondingly low pH value. If you want to make your own camellia soil, simply mix six parts of white peat with one part each of green compost, expanded clay, sand and bark compost. The ideal period for repotting camellias is between May and July. If the root ball of the pot is already strongly rooted, you can also repot the plants in autumn. This gets them better than if they had to spend the rest of the season in too small a pot.
If the soil is loamy, dig a very large planting hole and fill it with deciduous humus or special rhododendron soil before using the camellia. A drainage layer of lime-free gravel or chippings at the bottom of the planting hole protects against waterlogging. When cultivating in pots, a sufficiently large plant pot and good drainage are also essential.
Camellias, like almost all evergreen trees and shrubs, are cut-tolerant and can also be pruned more strongly if necessary. In mild regions of England they are even used for cut hedges. However, pruning is usually only necessary for younger plants so that they branch off well and grow into beautiful bushy plants. The best time for pruning is the spring before the start of the new shoot.
Avoid strong temperature fluctuations and dry heating air shortly before the flowering period, as many varieties then discard their flower buds. Water the camellia exclusively with rainwater or demineralised tap water and repot young potted plants about every two years after flowering. The root ball of your camellias should always be moist, but not stagnantly wet, as the fine roots of the plants die very quickly. Keep the plants dry from October: Remove the coaster and water only when the surface of the root ball is dry. Camellias tolerate rainwater best because, like rhododendrons, they react very sensitively to high lime contents in irrigation water. If the air humidity is low, for example in heated winter quarters, but also in summer on the terrace, you should occasionally spray the leaves with rainwater.
Commercially available mineral long-term fertilizers for rhododendron (e.g. Osmocote rhododendron fertilizers) or organic rhododendron fertilizers with guano are suitable as fertilizers for camellias. As soon as the new shoots become visible, you should spread the fertilizer on the pot balls. Since camellias have a high nitrogen requirement, but are also very sensitive to salt, it is best to halve the fertiliser recommended on the package. The long-term fertilizer dissolves over time and provides the camellia with all the necessary nutrients for several months. If you use organic rhododendron fertilizers, you will usually need to top up a little at the beginning of May. Alternatively, you can supply your camellias with liquid fertilizer for green plants every two to three weeks until the end of June. Conventional balcony flower fertilizer is less suitable because it contains too little nitrogen and too much phosphate. Halve the recommended dose for green plant fertilizers as well.
When hibernating camellias there are a few points to keep in mind. In this country camellia is mostly cultivated as a tub plant. It grows in winter-mild regions such as the Upper Rhine Graben and the coastal region also in the open, but then needs a protected location and must be provided in winter with a thick mulch layer and shaded with a fleece, otherwise the winter sun lets the leaves dry. Potted plants that have grown in well can tolerate frost to around -5 degrees Celsius without winter protection, outdoor plants with fleece cover to around -15 degrees Celsius. Late frost is usually the biggest problem for garden camellias, because the young shoots die off immediately at sub-zero temperatures.
A heated living room is not the ideal winter location for camellias. There the splendour of flowers is usually over after only a few days. The Williamsii cultivars, in particular, show flaccid petals when the temperature is too high, even when the flowers bloom. They are much better kept in a cold house or a weakly heated conservatory at temperatures up to a maximum of 15 degrees Celsius. Basically you should leave your camellia outside as long as possible in winter. Only from -5 degrees Celsius can the move to the winter quarters no longer be delayed. If you can’t offer your camellias optimal winter quarters (too warm and too dark), it’s best to put the plants back outside as soon as the frost period is over. By the way: Camellias need the cool temperatures, because the cold stimulus ensures that the flower buds open. The flowers can be kept at six to ten degrees ambient temperature for up to five weeks.
Important species and varieties
Nowadays, in addition to the varieties of Japanese camellia and the scented camellia (Camellia sasanqua), which already blooms in autumn, there is an unmanageably large number of hybrids with a wide variety of flowers, some of which are even multicoloured. Their ancestors all come from Asia. In this country, the garden shapes thrive as potted plants on the terrace without any problems. Some varieties are also suitable as garden plants in mild regions. In colder regions, the so-called Camellia Oleifera hybrids have proven their worth, which – provided with some winter protection – can withstand outdoor temperatures as low as -20 degrees Celsius. The varieties to be mentioned here include ‘Polar Ice’ (upright, medium-strong growth, white flowers), ‘Winter’s Dream’ (loosely upright growth, pink, semi-double flowers) and ‘Fire N Ice’ (compact growth, dark orange-red flowers).
Camellias can be propagated by cuttings. Depending on the species and variety, head cuttings, shoot cuttings, leaf cuttings or knot cuttings are used. If possible, however, you need a cultivation box with floor heating and a bright, semi-shade location. It can also take several months for the first roots to form. Some camellias, such as the Japanese camellia, also form seeds in our latitudes, which can be used for propagation and must also be kept warm. Professional gardeners usually multiply camellias by grafting.
Diseases and pests
In the winter-quarter, shield and wool-lice occasionally appear at the camellia . Typical fungal diseases are camellia death and Phyllosticta leaf spot disease. The camellia plague is highly infectious and very difficult to fight. It manifests itself through a brownish-red discoloration of the flowers, which usually begins in the middle of the flower, often accompanied by a mould-like coating. Light-flowered varieties are particularly susceptible.