All of the 267 species recorded within the genus Camellia
originated from Asia except C. lanceolata , which is a
native of the Philippines and Indonesia. In China, Camellias have
been used in the last three centuries as ornamental plants, and
to provide food from fermented young leaves, cosmetics, culinary
and industrial oils, high grade charcoal for fuel, and tea. In Japan,
green tea made from leaves of Camellia sinensis that have
been steamed, rolling and dried, is an integral component of the
tea ceremony. Besides its cultural significance, Camellias have
been used in Japan in textiles, ceramics, brewing, cooking, household
utensils, tools, printing, crafts, farming, fuel, medicine and foodstuffs
and cosmetics. Camellia plants have also been used as roadside trees
and fences. Camellia is the symbolic flower in more than 30 Japanese
Camellias were introduced into Europe in the 17th century with
the beverage tea, and later became treasured as ornamental flowering
plant. They were introduced into the United States in 1774 to establish
tea growing, but this venture failed. Ornamental Camellias did not
became established in the United States until enthusiasts began
seeking perfect blooms around the 1940s, many years after the first
flowering cultivar was imported to New Jersey in 1797. Ornamental
Camellias were introduced from England to Australia in 1826. They
were introduced into New Zealand soon after by missionaries and
others from Australia, and from England by British settlers. Some
of the oldest Camellia trees in New Zealand are found in Akaroa,
which was established in 1840 by French colonists.
Some species of Camellia are still grown for their economic value.
The leaves of C. sinensis L. var. sinensis and
C. sinensis var. assamica are used to make tea.
Crushed seeds of some species such as C. oleifera , C.
chekiangoleosa , C. reticulata , C. grijsii ,
C. vietnamensis , C. crapnelliana and C.
gauchowensis are cultivated for production of high quality
oils. The oil is used in cosmetics and for cooking, while other
Camellia products are used by pharmaceutical and manufacturing industries.
Production of tea oil from C. oleifera is currently under
investigation in Georgia, US. The oil is used in cooking and in
the cosmetic industry, with process residues being considered for
livestock feed and insecticide formulations.
Green tea recipe
Camellia sinensis , the tea plant, is used to make the
tea we drink. There are many different processes used to dry the
leaves for making the beverage. There are also many varieties of
C. sinensis used to make tea, with villages in China having
their own strain of tea plants with different qualities. There is
even a tea variety developed in China that does not have caffeine.
Try this Chinese recipe for green tea. The tea is reported to be
delicious, very smooth and not bitter.
Pick young shoots with 2-3 leaves from C. sinensis .
Roll several shoots between your hands until the leaves darken
and become crinkled. Bruising the leaves allows the fermentation
process to begin. Do not break the leaves into pieces.
Place thin layers of leaves on a tray in a shady location and
allow the fermentation process to occur over 2-3 days.
Dry the leaves in an oven at 106°C (250°F) for 20 minutes.
This step is necessary to remove all the water in the leaves and
stop the fermentation process.
Store the tea in an airtight container, or use immediately.
Most Camellias are now grown for their ornamental value. Camellia
flowers have been selected for centuries to produce a wide range
of colours, flower forms (single, semi-double peony, anemone, rose-form
double and formal double), and sizes (1-23 cm) (Figure 1). The most
popular ornamental species of Camellia are C. sasanqua ,
which flowers in autumn and winter, and C. japonica
L. and C. reticulata, which flower in winter and
spring. Inter-specific hybridisation has led to around 5600 hybrids
being registered worldwide.
Figure 1 : Flowers of Camellia japonica cultivars
(clockwise from top left) Little Michael, Nuccio's Pearl, Wilhelmina
and San Dimas.
There are 32,000 entries of Camellia cultivars in the International
Register, but many of these are invalid names - synonyms, duplications,
etc. Many entries represent extinct cultivars, where the names have
been extracted from books produced in Japan and China hundreds of
years ago, as well as in Europe in the 19th century. So the number
of valid entries is possibly around 15,000.
Camellias represent an important part of the nursery trade in New
Zealand. The Camellia industry generates about $2-4 million worth
of domestic sales and $0.4 million in export sales annually. Most
of the plants are used for amenity or ornamental purposes.
A garden shaded by deciduous trees provides ideal conditions, including
good sunlight with high humidity, temperatures below 15°C in
winter, and shade in summer. Soils should be rich in humus, porous,
and slightly acidic (pH 5.5). Camellias also survive well in pots.
To encourage flowering in potted plants, use a general potting
mix consisting of 500 g of 12-14 month release Osmocote Plus (15%
N, 3.5% P, 9.1% K, 1.2% Mg, plus traces of B, Cu, Fe, Mn, Mo and
Zn) in 200 L of bark and 50 L of sand. Re-pot every two years. An
alternative soil mix is one-third each of decomposed compost, garden
soil and moss peat.
If the potting mix has no fertiliser in it, add fertiliser weekly
to each pot during spring, immediately before flowering, ceasing
application by early summer. Use 2 g of an ericaceous fertiliser
(one suitable for azaleas or rhododendrons) mixed in 1 L water per
Camellias in the garden will normally thrive without fertiliser.
However, they will respond with improved growth and flower vigour
to an ericaceous fertiliser applied once in early spring prior to
flowering. Apply fertiliser to soil under the drip line of each
plant at a rate of half that recommended on the label. Water the
fertiliser into the soil. Avoid using lime, which will increase
the pH and create a basic soil.
Camellias can die in dry soils. Water the soil around Camellias
regularly but avoid creating waterlogged conditions. Soils do not
require watering if they feel moist to the touch.
Pruning of 1-3 year-old Camellias encourages earlier and better
branching. Cut the main shoot of 1 year-old bushes back to a length
of 10-15 cm to encourage outward branching.
Prune older bushes to the space available, and the second batch
of new shoots produced by some cultivars, which may cause an undesirable
shape in the bush.
Prune immediately after the new shoots have started forming, after
flowering has finished. Cut the selected branch 2 cm above a set
Misshapen bushes can be trimmed to the trunk using a technique
descriptively called 'Hatracking' (Figure 2). The bush will regenerate
and produce flowers in the next flowering season.
Figure 2 : Hatracking of Camellia bushes at the Wellington Botanic
Camellias can be propagated vegetatively from a single Camellia
cultivar, and generatively from two Camellia cultivars or species,
by different methods.
Seedlings are propagated from a low-hanging downward-pointing branch
of a Camellia bush that is more than two years old. Remove all leaves
and shoots of the branch except for a few leaves at the tip. Cut
a small incision near the tip of the branch, and train the branch
down to the ground or into a pot containing standard potting compost.
Secure the tip in the soil with a peg, heap peaty soil over it and
keep it moist. After two years, roots will have formed from the
incision, and the shoot tip can be separated from the mother bush
With this most successful propagation method, new plants should
flower after one year. Take cuttings in February. From the mother
plant, select a top shoot that has at least two leaves and no buds,
and is 15 cm long and olive green (signifying the optimum level
of maturity). Cut the stem diagonally 2 cm below the lowest leaf
using a sharp knife that has been sterilised in alcohol. Dip the
cut surface into a rooting powder. Push the cutting 2 cm deep into
sterilised potting mix (heated in a fan oven at 120°C for 40
minutes) in an 8 cm diameter pot. Cover the pot with a stiff plastic
bag and seal the bag to the pot with string. Incubate under shade
at 25°C until roots form (8-12 weeks). Then remove the bag,
and incubate at 16°C for a further four months when the seedling
can be re-potted in Camellia soil.
Root stimulation from stems
During the growth phase (after flowering), remove the leaves on
a 30 cm length of stem on a selected mother plant. Make two incisions
2 cm apart around the circumference of the stem, and peel off the
bark skin. Tie the end of a section of a transparent cylindrical
plastic bag below the scar. Fill the bag with moist moss peat. Then
tie the bag around the stem above the incision. Once roots appear
inside the peat-filled bag, separate the shoot with its new roots
from the mother bush, and plant it in an 8 cm diameter pot filled
with Camellia soil.
This method is suitable for cultivars that do not produce roots
readily. Camellia japonica and C. sasanqua
are good stock species. Cut the base of the scion of the cultivar
to be propagated into a wedge, and insert the wedge into a slot
cut into the stock. Secure the scion with grafting tape or cotton
wound tightly around the join. The two pieces will fuse together
within eight weeks.
Raise your own Camellia by crossing cultivars of the same or compatible
Camellia species. Transfer ripe pollen grains from the anther of
a flower or number of flowers of one Camellia bush to a ripe stigma
(recognised as receptive by secretion of a mucus). Cover the recipient
flower with gauze until fertilisation has occurred (recognised by
petal drop) to avoid inadvertent pollination from other genotypes.
Under favourable climatic conditions, a woody seed capsule the size
of a walnut will have formed by autumn. It will open naturally to
release up to six blackish-brown seeds.
Test the resulting seeds for viability by placing them in a bowl
of water. Seeds that sink to the bottom after 10 minutes are viable.
Those that float are sterile and incapable of germination.
Press three seeds per pot about 25 mm deep into potting mix contained
in a 10 cm diameter pot. Cover with peat, and water. Place a transparent
plastic bag over the pot and incubate at about 20°C. Remove
the bag after the seedling develops two leaves (3-5 weeks). Prick
out each seedling once it has grown a total of four leaves, into
an individual pot containing Camellia soil. Re-pot as necessary.
Flowering should occur 3-5 years after sowing.
In New Zealand, strongly growing Camellia bushes are generally
free from invertebrate pests and diseases. However, Camellias can
be susceptible to a number of disorders, insect pests and fungal
pathogens present in New Zealand.
Physiological disorders result from climatic changes, nutritional
imbalance or inadequate drainage, and can usually be rectified by
changing the environmental conditions. Algae and lichen may grow
on leaves in shady humid conditions. They have no effect on the
health of the plant but can be controlled with a spray of copper
oxychloride. Camellia cultivars with white or pale pink flowers
are more delicate than cultivars with darker-coloured flowers and
may develop brown petals from exposure to sun or wind. Shading from
extremes of weather and careful pruning to prevent blooms from rubbing
against other parts of the plant are recommended. Extreme frost
or changes in temperature can induce buds to drop before flowering.
Transferring the plant to a more sheltered part of the garden could
solve this problem.
Chlorosis of the leaves could be due to natural senescence, a genetic
condition, or it may be caused by extended dry periods resulting
in dehydration, or an excess of water with poor drainage. Chlorosis
caused by alkaline soils, which prevent iron and other nutrients
being available in a soluble form, can be ameliorated by applying
acid fertilisers, compost, and iron chelate or iron sulphate. Yellowing
between green veins in the leaves can indicate lack of iron or magnesium,
readily corrected by application of sulphate of iron or magnesium
sulphate. Corky scabs on the undersides of leaves can result from
plants absorbing more water through the roots than the leaves can
transpire (oedema), and can occur through over-watering. It can
also occur in Camellias with a large root mass and little foliage.
Bronze patches on leaves can occur in some cultivars exposed to
hot sunny conditions as a result of sunburn. Shade solves the problem.
Potassium deficiency can result in brown patches on leaves and can
be corrected with potassic superphosphate. An excessive build-up
of salts in the soil can result in edges of leaves turning brown,
and is usually corrected by thorough watering to wash the salts
from the immediate root zone.
Sucking insects including scale and aphids, which may affect the
vigour of Camellia plants less than 5 years old, require treatment
with insecticides. The scale insect Pulvinaria floccifera
can severely affect young bushes. They can be effectively controlled
by spraying the bushes with Attack ® (a mix of permethrin, primiphos-methyl
and hydrocarbon liquid) at 1 mL/L water until run-off. Aphids can
be controlled easily with an readily available aphicide from your
garden shop. These insects secrete sugars that black sooty moulds
then feed on. Controlling these insects will also stop new mould
growing on the leaves, but the old mould may require wiping off
to remove the unsightly blemish.
Beetles of grass grub Costelytra zealandica and bronze
beetle Eucolaspis brunnea , and larvae of case moth Liothula
omnivorous , chew the leaves of Camellia plants, but they rarely
affect the vigour of mature Camellia plants and have no effect on
Viruses can infect Camellias, but their effect is usually minor
and aesthetic. Viruses can cause irregular blotches of white on
coloured flowers, and irregular blotches of yellow or pale colour
on the foliage. A virus causes ringspot, identified by faint green
rings in young leaves that turn bright green with dark edges within
yellowing leaves as they mature. Viruses can be introduced by grafting
on to infected stock, and by using scions from infected plants as
cuttings. Some breeders do this on purpose to create a variegated
leaf in a new line of Camellias.
Fungal diseases of Camellia plants are more serious. Dieback caused
by the fungus Glomerella cingulata can be lethal to Camellias.
Symptoms include sudden death and wilting of young shoots, followed
by the dead leaves holding on to the shoot, and dying of tissue
and growth of a canker, which continues to enlarge, extracting water
and nutrients causing yellowing of leaves, loss of foliage and dieback
of twigs and branches. The wind-borne fungus Exobasidium
spp. affects young leaves at the ends of branches, causing them
to become light green to white, or deep pink to red. Phytophthora
cinnamomi is the main fungi of several species that cause
root rot. Root rot disease is common in waterlogged non-aerobic
soils. Symptoms are expressed in summer, when leaves become yellow
and die, and branches wilt and die back from the tip until the whole
plant dies. Roots of an affected plant will be dark brown and brittle,
and contain few white fibrous roots essential for a healthy plant.
Two fungal diseases of flowers are of concern because of the importance
of Camellias for their flowers. Botrytis cinerea causes
botrytis flower blight or grey mould, characterised by water-soaked
brown spots on the petals. The spots spread fast to form tan to
grey-brown blotches associated with the blighting and ecay of blooms.
Colours on diseased flower petals quickly fade as the flower withers
into a brown-grey wrinkled mass. The disease is prevalent when relative
humidity exceeds the threshold of 93% for when botrytis spores infect
the petals. Consequently, the disease can be a problem in glasshouse-grown
Camellias. The other flower disease is Camellia flower blight, otherwise
known as Camellia petal blight.
Since Camellias are most commonly grown for their attractive flowers,
the most important disease affecting Camellias is Camellia flower
blight, as the premature browning and fall of infected flowers detract
from their aesthetic value and can make blooms unfit for showing
(Figure 3 ). Camellia flower blight is caused by the sclerotial-forming
fungus Ciborinia Camelliae , and is specific to flowers
of most species of Camellias. The pathogen does not affect Camellia
Camellia blight was first identified in Japan in 1919 and first
found in the United States in California in 1939, spreading to most
states where Camellias are grown within the next 50 years. In New
Zealand, the disease was first reported in Wellington in 1993. It
is present throughout New Zealand in most regions north of Ashburton.
Figure 3 : Symptoms
of Camellia blight, comparing healthy and blighted flowers
on Camellia Gwenneth morey.
While the symptoms of flower blight are similar to those of Botrytis
infection, with browning and premature dropping of flowers, the
diseases are easily distinguishable from one another. With flower
blight, the entire and intact whorl of petals (corolla) separates
easily from the receptacle, leaving a characteristic grey ring of
fungal hyphae at the point of separation (Figure 4). With Botrytis
, the petals come away separately, with no sign of grey fungal
growth on the broken surfaces.
Figure 4: Early C. Camelliae infection
in a Camellia flower (left), and advanced flower infection (right)
showing growth of mycelium at the base, which eventually will
develop into sclerotia in fallen flowers. Sclerotia of assorted
sizes (bottom) can be found at the base of infected bushes.
The pathogen has a simple life cycle (Figure 5). Wind-borne spores
arising in late winter and spring from the apothecia of soil-borne
sclerotia infect the flowers of Camellias, and develop within the
fallen flower to form new sclerotia. These produce apothecia in
Current control strategies are aimed at interrupting the lifecycle
of the pathogen by preventing formation of sclerotia or apothecia,
thereby preventing the release of ascospores, or by preventing infection
of flowers on Camellia bushes.
Limiting its spread
The spread of the disease from an endemic area, and its introduction
into new locations could be restricted by only transporting Camellia
plants that are free of flowers, and as bare-rooted cuttings or
scions. These measures aim to prevent old sclerotia in the soil
or potential sclerotia in infected flowers from being transported
along with the plant. It would be extremely effective if adopted,
but home gardeners and many nurserymen often do not recognise that
the pathogen is present when purchasing or transferring cuttings.
Home gardeners who select their plants on the appearance of the
flowers are also unlikely to purchase bare-root cuttings that are
too young to flower. Once the disease is established in a region,
a number of cultural and chemical methods can be used to prevent
may be avoided by growing autumn-flowering species such as C.
sasanqua , or cultivars that flower early in the season before
apothecia are produced by the soil-borne sclerotia (mid-late July
in New Zealand). While this approach might be effective, most growers
of Camellias prefer to have Camellias flowering during the winter-spring
period, when apothecial production is at its peak.
The fallen infected Camellia flowers may be raked up and burned
to kill the developing sclerotia. A plastic sheet laid underneath
flowering bushes makes collection of fallen flowers easier, and
prevents apothecial development from sclerotia underneath. This
approach would be highly effective if adopted universally, but is
practised by only a few Camellia growers. Further, home gardeners
do not usually burn the flowers, instead adopting the easier approach
of discarding the flower debris in compost. As sclerotia may survive
composting, council or private green-waste composting schemes can
contribute to the spread of the disease.
Moisture levels on the ground where the sclerotia fall can be reduced,
thereby depriving the sclerotia of moist conditions for subsequent
development. This can be achieved by trimming the lower Camellia
branches to about 0.5 m above ground, raking off loose-leaf litter
and weeds to expose bare soil, or by covering the exposed ground
with either black polythene or 75-100 mm thick pine needles. Adding
ground cover could also be effective in smothering the soil-borne
sclerotia and suppressing apothecial production from sclerotia underneath.
However, these methods would have limited control of apothecia produced
by sclerotia developing in flowers that fall after the ground cover
has been applied. The apothecia could still form in wet seasons
or after periods of rain.
Fungicides can be applied to soil under Camellia bushes to prevent
production of apothecia by sclerotia, or they can be sprayed on to
the bushes during flowering to protect blooms from infection by ascospores.
Alternatively, cut blooms can be dipped into fungicide solutions prior
to display at flower shows.
Application of fungicides
to soil immediately prior to apothecial production has generally
given effective control of apothecia. Alto ® 100SL (100 g/L
cyproconazole) or Shirlan ® 500SC (500 g/L fluazinam) sprayed
on to infested soil at 4 L/ha in 1000 L water/ha in early August,
and reapplied 3-4 weeks later, can be effective in preventing production
of apothecia during August to November. No fungicides are registered
in New Zealand for use against C. camelliae , so the risk
in controlling the pathogen is borne by the user.
Many foliar-applied fungicide sprays have been evaluated for protection
of flowers against infection by ascospores, but generally they have
not been successful in controlling the disease. For any degree of
effective protection, the fungicides needed to be applied repeatedly
during flowering. Bayleton ® 5 DF (50 g/kg triadimefon), applied
at 1 g/L water to Camellia bushes weekly during flowering, only
reduced numbers of blighted flowers by 31–77% in every season
over six years in the United States. In New Zealand, Camellia bushes
sprayed fortnightly until run-off with either Alto ® 100SL at
0.15 mL/L or Shirlan ® at 1.0 mL/L water, both containing a
surfactant to help spread the fungicides during the 8 weeks of flowering,
had disease levels similar to that of the untreated control (17%).
Dipping Camellia blooms into fungicide solutions has been shown
to be effective in preventing infection of cut flowers. Healthy
Camellia blooms dipped into a solution containing Cereous 250EC
(250 g/L triadimenol) at 2.0 mL/L water, or Bayleton 5DF (50 g/kg
triadimefon) at 4.0 mL/L water plus a few drops of washing up detergent,
for 5 min 1–7 days prior to showing, can effectively delay
the onset of the disease.
However, none of these strategies are sufficiently effective or
practical for ready adoption by Camellia growers.
strategy for integrated biocontrol of Camellia flower blight was
developed in a PhD project at Lincoln University. Two approaches
were examined. One approach was to protect Camellia flowers against
wind-borne spores arising from the sexual fruiting bodies by either
stimulating the plant's natural defence systems or spraying naturally
occurring microbes on to the flowers, but this approach was only
partially successful. Although isolates of naturally occurring leaf-surface
microbes such as Bacillus , Pseudomonas , Aureobasidium
and Cladosporium spp. provided almost complete protection
against Camellia blight in petal assays (Figure 6), they did not
prevent symptoms on whole flowers on Camellia bushes, even after
repeated applications with or without additives that were added
to the formulation to aid spread of the antagonists over the flowers.
It appears that the microbes were not able to colonise the burgeoning
blooms in competition with other microbes in sufficient numbers
to provide protection against infection.
Figure 6: Bio-protection of
The other approach was to attack the soil-borne sclerotia with
naturally occurring microbes and soil amendments, and thereby prevent
apothecial production. Screens of 400 candidate microorganisms isolated
from sclerotial baits and decaying sclerotia (Figure 7), two isolates
of Trichoderma and an isolate of Fusarium lateritium
reduced the number of viable sclerotia by 38-50%. This indicated
that moderately parasitic micro-antagonists were present in soil
under Camellia bushes.
Figure 7 : Ciborinia camelliae mycelium growing from
healthy sclerotia (top left), and species of Trichoderma
(top right) and other fungi (bottom) growing from parasitised
A range of soil treatments was also investigated in field trials
in an attempt to reduce the viability and germination potential
of over-wintering sclerotia. Nitrogenous fertilisers that contain
cations have been shown by other researchers to stimulate microbial
degradation of sclerotia of other pathogen species. Urea applied
to soil at 10 g urea/m² (46 kg N/ha) in February and again
in June reduced field populations of C. camelliae sclerotia
by 64% in the following November. We think this reduction was due
to stimulation of parasitic microbes.
The direct toxic effect of selected fertilisers on apothecial production
was also tested. A single application of the fertiliser calcium
cyanamide at 500-1000 kg/ha to soil under Camellia bushes immediately
before flowering (July-August), was found to give complete suppression
of apothecial production. This treatment could be used for short-term
control of the disease. Calcium cyanamide decomposes naturally in
the soil to urea, and so this may also aid in the reduction of sclerotia.
Potassium bicarbonate and ammonium bicarbonate gave partial suppression
(76-87%) of apothecia at the 300 kg/ha rate tested in the trial,
and presumably could be more effective at higher rates.
Tree mulches can also stimulate parasitic microbes in the soil.
Covering soil under Camellia bushes with 100 mm thick mulches from
trees such as pine, gum, and manuka, for 9 months resulted in total
suppression of apothecia and a 77% reduction in the population density
of soil-borne sclerotia, compared to bare soil. The different species
of tree mulches had a similar effect on reducing numbers of sclerotia.
However, the tree mulches had no effect on the new generation of
C. camelliae sclerotia developing in fallen flowers, which
would produce fruiting bodies in subsequent years.
The successful control strategies developed in this study could
be integrated into a programme for effective control of Camellia
blight. Urea applied at 20 g/m² (200 kg/ha) to soil beneath
Camellia bushes followed by a 100 mm thick layer of tree mulch should
result in significant suppression of apothecia, thereby preventing
infection of flowers, and resulting in a gradual decline in numbers
of soil-borne sclerotia.
Thanks to Dr Vince Neall, President of the New Zealand Camellia
Society, for critiquing this manuscript.