Camellia (genus Camellia) is an evergreen shrub belonging in the family Theaceae. It is an attractive garden addition and relatively hardy, providing gardeners meet its growth requirements. There are various cultivars well adapted to growing in USDA planting zones 7 through 9. Large, rose-like flowers bloom in spring and again in winter in colors of pinks, oranges, reds, yellows and purples. Plants prefer acidic, well-draining soils. Several diseases and pests bother camellias but are treatable and avoidable with pesticides and proper planting.
Rot rot (Phytophthora and Pythium) is a condition leading to the camellia’s death. The condition develops when plants are overwatered, planted in a moisture-retentive soil that is too heavy or planted in a container that is too large. Plants usually start performing poorly and the foliage begins to yellow, with leaves easily falling from the plant as you run your fingers down the stems.
Symptoms of root rot are controllable by planting outdoor camellias in well-draining soil mediums that do not have a tendency to retain water. If soil conditions are too wet, amend the site with sand and peat moss, or plant in a raised bed. Water camellia plants only when necessary. Use well-draining potting mixes when growing camellias inside containers, and use a container that is approximately 1 1/2 times larger than its root ball. Gardeners tend to overwater plants grown in big containers, and root rot develops.
Camellias infected with algal spot (Cephaleuros virescens) have small raised areas, such as blotches, covering their leaves. The raised areas are usually grayish-silver, greenish or tan, with green margins running through the affected leaf. Plants with heavy infestations may have leaf drop or yellowing. The condition is most damaging to plants that are weak.
Too much moisture and sunlight, not enough airflow and high temperatures usually cause the condition. Since there are no fungicides to control the problem, gardeners can prune away infected areas of the plant and selectively prune the branches to open the plant up and create more air circulation.
Scales are small insects that are problematic with camellia plants during periods of warm weather. Females lay their eggs when temperatures range between 86 and 91 degrees F. In warm regions such as Florida, scales reproduce year-round, creating problems all year. In cooler areas, scale outbreaks generally coincide with the arrival of warm, springtime temperatures. Affected leaves look variegated on their tops, with the bottoms covered in clusters of a white, fuzzy substance and insects.
Camellias infected with scales require pruning to remove infected leaves and open up the plant so it receives better air circulation. Spraying the foliage with pesticides, insecticidal soaps or oils kills the insects, with a repeated application required every week for two to three weeks, as scale is sometimes hard to control. Gardeners should treat the scale outbreak as early as possible in spring.