If you’ve been to the seashore in the northeastern United States, you have definitely seen Japanese black pines. Because of their high tolerance to salt spray and saline soil, the rugged trees used to be one of the first choices for sun-drenched beachfront plantings. If grown in ideal conditions, Japanese black pines can reach a height of 80 feet or more.
The Japanese black pine is a not the same tree as black pine (Pinus nigra). The Japanese black pine grows irregularly and asymmetrically without a central leader. The rigid needles, five to seven inches long, are exceptionally dark green. Unlike most conifers, the buds are prominent—one-half to three quarters of an inch long and silvery white, forming an attractive contrast with the dark green needles.
In addition to being tolerant of wind, drought and salt, the Japanese black pine is also tolerant of deer, which usually don’t find the tree palatable.
However, if you like to keep your backyard neat, Japanese black pine might not be the right tree for you, as it litters its surroundings with a substantial number of cones, twigs and needles.
|Botanical Name||Pinus thunbergii|
|Common Name||Japanese black pine|
|Plant Type||Evergreen tree|
|Mature Size||15 to 50 feet height, 20 to 35 feet width|
|Sun Exposure||Full sun|
|Soil Type||Sandy, silt, loamy|
|Soil pH||5 to 6.5 to 8|
|Native Area||Japan and Korea|
How to Grow Japanese Black Pine
Japanese black pine transplants well if you get a balled and burlapped tree from a nursery.
Because the tree has an irregular growth pattern, it will likely require regular pruning to make room for people and vehicles to pass underneath the canopy.
If grown in ideal conditions, the tree does not have many insect or disease problems. However, in the last thirty years, environmental stress factors such as changing weather and climate patterns have provided less than ideal conditions. Japanese black pine trees have been affected by and died from several pests and diseases. This has led to its drop in popularity as a seashore tree.
There is also the option to grow a dwarf Japanese black pine as a bonsai.
Japanese black pine should get six hours of direct sunlight. Some light afternoon shade is acceptable.
The soil must be moist but well-drained. Japanese black pine does not tolerate soggy soil and poor drainage. It prefers acidic soil but can also grow in slightly alkaline soil.
After you plant the tree, water it weekly in the absence of rain for at least the first year. After the tree is established, it is drought-tolerant.
Temperature and Humidity
In locations with temperatures below ten degrees below F, the needles dry and turn brown as a result of winter burn.
Only a soil test can tell you the quality of your soil. If your soil is poor in nutrients, add a complete fertilizer in the spring.
Grown in Containers
With regular pruning, Japanese black pine can be successfully trained as a bonsai. It is in fact is one of the hardiest trees for bonsai growing.
If you keep it outdoors—or bring it outdoors for the summer—the container must be protected from the hot sun to prevent root burn. In partial shade, the needles will be lighter than a tree grown in full sun.
Water it regularly but let the soil dry out to the touch between watering.
In a container, Japanese black pine needs more frequent fertilizing, about every two weeks during the growing season.
Pruning stresses the tree and causes sap bleeding. Do substantial pruning only between fall and early winter. If you need to do minor pruning during the summer, make sure to move the container into the shade for about a month afterwards to minimize sap bleeding.
Varieties of Japanese Black Pine
'Thunderhead' is a dwarf cultivar that grows to about six feet high in ten years.
‘Oculus Draconis’ is a variegated variety. The needles have a yellow band close to their base.
‘Pygmaea’ is a compact cultivar with full-length needles. It grows only about five feet in ten years.
‘Shirone Jamone’, another variegated cultivar, has bright golden or yellow bands on dark green needles. In ten years, it grows up to ten feet high and seven feet wide.
When grown in optimal conditions similar to its natural habitat, Japanese black pine has few problems but when it’s under stress, it can be susceptible to a range of diseases, including diplodia tip blight, twig or needle blight, rusts, cankers, leaf cast, and pine wilt disease.
Possible pests include sawflies, Nantucket tip moth, pine wilt nematodes, pine sawyers, and the black turpentine beetle.
The best way to identify the problem is to contact your local Cooperative Extension office and bring in a sample for diagnosis.