Norfolk Island Pines (Araucaria), native to a small island in the South Pacific, are common houseplants. In the wild, Norfolk Island Pines can reach 200 feet tall and 10 feet across. As houseplants, Norfolk Island Pines are adaptable and easy to maintain. Most of the diseases that affect these plants result from improper care. Good care also reduces insect problems, since most insects attack already stressed plants.
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Ideally, Norfolk Island Pines should be kept barely moist. Over-watering leads to loss of vigor and eventual death from stunted and rotted root systems. If your plant is suffering from root rot (caused by a fungus such as Cylindrocladium or Pythium), unpot the plant and knock off as much soil as possible. Trim off all damaged roots, and then place into a pot with good drainage filled with a sterilized potting soil. Treat the roots with a fungicide, available at a garden center or hardware store. After repotting, water sparingly, keeping the soil barely moist. It is better to let the plant dry out a bit before watering than to over-water.
Inadequate feeding results in pale green or yellow growing tips (chlorosis). Feed plants every three to four months with an all-purpose houseplant fertilizer or one intended for foliage houseplants. This is especially important for large plants that have been in a pot for a long time–these plants will have used all the nutrients in the potting soil. Every three to four years, repot your plants into a larger pot filled with good quality potting soil, such as African violet potting mixture. Trees too large to repot should be top-dressed–remove the top 2 or 3 inches of soil from the pot and replace with fresh potting medium.
Anthracnose or Needle Necrosis
This disease starts as small dead areas on the needles. If untreated, branches turn brown and needles fall. This fungal disease (Colletotrichum derridis) is caused by overhead watering. Water plants at the roots only. Treat diseased plants by pruning off infected areas and applying a fungicide. Follow package application directions carefully.
This disease causes the lateral branches to droop down even though the main trunk is straight. Affected plants languish and develop poorly. Too-low light levels cause branch Droop. Norfolk Island Pine prefers bright indirect light or curtain-filtered sunlight and can take full sun in the winter. Move your plant into an area with brighter natural light or supplement available light with artificial lights. Plant lights are available at garden centers and hardware stores.