Pineapples are native to Southern Brazil and Paraguay. They are an herbaceous perennial of subtropical to tropical habitat. Pineapples began to be grown commercially around 1720 in greenhouses. The fruit is the standout. A prickly leaved large fruit with spiny ends, the inside is a juicy yellow to golden sweet fruit. It can grow 12 inches tall and weigh up to 4.54 Kilogram. Pineapples should be grown in well-drained soil in a warm location with generous, nitrogen-rich fertilising every three to four months, while the fruit is growing. There are several diseases and deficiencies that can cause a pineapple plant's leaves to yellow.
Crookneck is caused by zinc deficiency. It is characterised by deformed heart leaves that become waxy and brittle. The leaves also turn a light yellowish green. Yellow spots can form on leaves and become small blisters. The blisters become greyish or brown and sunken. The fruit actually grows sideways in a nearly prone position. Treatment is a 1 per cent solution of zinc sulphate. Care should be taken with application levels as excessive treatment can cause healthy leaves to die on the tips and the older leaves to turn yellow.
Yellow Spot Virus
Yellow Spot Virus is transmitted by the Thrips tabacii. This pest is the onion thrip and generally bothers plants in the allium--garlic and onion--family. It causes striations and yellow striping on the leaves of the pineapple. The treatment is to control the thrips. A good insecticidal soap applied every couple of days should provide adequate control. Treat nearby plants as well, since the insects travel.
Pineapples need to be transplanted annually to keep soil clean and give the plant room to grow. However, the root system is shallow and easily damaged. Transplant shock can lead to yellowing and dying leaves and is an indication the plant is stressed. It normally goes away after the loss of some leaves, but an application of vitamin B-12 or a transplant fertiliser helps normalise the plant's condition and slows leaf loss.
Pineapples need regular fertilising with a nitrogen-rich formula. A slow-release formula is best so the nutrients don't overwhelm the plant's abilities to metabolise them. Too much of a nutrient can cause fertiliser "burn," which can affect not only the leaves but also the roots and other plant systems. A slow release every three months or a liquid well-diluted in water at every watering keeps the plant healthy, but limit the supply of potentially toxic minerals.
Humidity and Temerature
Humidity needs to be high for pineapple plants to thrive. A humidifier in the room where the plant is kept will keep the plants leaves moist and avoid the dry yellow tips that sometimes occur. Yellowing of leaves can also happen if a plant is too cold. Keep it away from draughty windows and maintain a temperature of around 70F.