Pine trees (Pinus spp.) are coniferous evergreens with clusters of long, slender needles. The trees grow between 30 and 100 feet tall in U.S. Department of Agriculture plant hardiness zones 2 through 10, depending on the species. While there are advantages to planting pine trees, such as year-round green, fragrant needles, the ability to grow in poor soils and minimal pruning, there are also some disadvantages.
Needles and Cones
Pine trees, like other needled evergreens, drop needles. Though they are evergreen, periodic needle shed occurs as new needles grow. Unlike the leaves of deciduous trees that can be raked up fairly easily and used for mulch, pine needles are difficult to remove. They can be used for mulch if you are able to pick them up, but their more acidic properties mean they should be used in moderation. The cones also drop. If the tree is planted near a lawn, the dropped cones can cause problems for mowers if they aren't removed.
Pine trees exude a sticky sap. The sap can get all over your hands if you try to collect the needles or cones that fall around the tree. The sap also attracts insects. Some of these insects, such as butterflies, may be welcome. But other insects such as beetles and weevils are also attracted by the sap; they then cause damage to the tree when they bore into the wood. Pruning during the winter dormant period -- when the injury won't produce as much sap to draw pests -- helps to reduce insect problems.
While most pine trees will grow in poor soils with low levels of nutrients, they need an acidic soil pH below 7.0 to thrive. Alkaline soils can cause chlorosis, or yellowing of the needles, as well as poor growth rates and stunted growth. The trees also need a soil with good drainage, and they can have problems in heavy clay soils. If your soil is not naturally acidic, this soil requirement is a disadvantage. Many pines species are also sensitive to air pollution and do not grow well in urban areas.
Pine trees have their own specific diseases that tree owners must guard against. Pine wilt is spread by a nematode carried by beetles. Soon after infection, the needles turn reddish-brown and the tree dies. There's nothing you can do to save the tree; instead, you must remove it from the area and burn or dispose of it to prevent the disease from spreading. Needlecast is caused by a fungus and also affects pines. Needles die, and without a fungicide treatment, the tree may die.