Tall and stately northern pine trees grow to a height of 90 to 100 feet. They're known for their bluish-green needles and slender, yellow-brown cones, and don't require a great deal of care. Northern pines are also known as white pines or northern white pines. These fast-growing evergreens thrive in cool, humid climates. Seedlings grow well in partial shade for the first 5 years, and full sun thereafter.
Newly planted or transplanted northern pine trees should be watered regularly for the first 3 to 5 years to establish a healthy root system, especially in the summer and/or periods of drought. Continue watering until the ground freezes to reduce winter damage. Before watering, check the soil moisture with a soil probe 6 to 8 inches deep to confirm that the soil isn't soggy. Using a garden hose or drip system, water the entire root system so moisture penetrates 12 inches down into the soil.
Mulching a northern pine with a 3-foot diameter of organic material such as leaves, needles or bark will help to maintain the tree's health, improve water retention, reduce weeds and insulate the roots from cold temperatures. Mulch should be 2 to 3 inches deep, though not applied against the bark of the tree. The mulch will break down over time and should be reapplied each year. Rake the existing mulch before adding more, to break up compacted layers.
It's typically not necessary to fertilize a northern pine tree unless the soil is tested by a laboratory to be deficient of nutrients. A basic soil test will provide readings on organic matter, pH and nutrients. Your soil's results may include timing and quantity recommendations for applying a complete nitrogen-phosphorous-potassium fertilizer. Always confirm that the soil is moist, and not extremely hot or frozen, before applying fertilizers.
Pruning northern pine trees reduces insect damage and helps the trees grow straighter. It's important to not remove too many branches at a time, which will slow the growth. Always leave at least two thirds of the branches and prune during fall or winter, the tree's dormant seasons. Use pruning shears or a pruning saw, and leave branch stubs.
Staking may be necessary for northern pine trees during their first 1 to 3 years of life while the roots are growing and beginning to stabilize the tree. Check the attachment points of the staking every 3 to 6 months and loosen if necessary. The staking should be removed within 1 year of installing to prevent damage, and a new one installed only if the tree still can't stand on its own.