Black Pine - Pinus thunbergi
iGeneral Information: An
excellent, small, irregularly-shaped Pine, the size and
shape of Japanese Black Pine is variable reaching a
height of 25 feet and a spread of 20 to 35 feet. The
exceptionally dark green, five to seven-inch-long
twisted needles are borne in groups of two.
Although trees may or may not have a central leader
prune to develop
one if the tree will be grown to a large size. Branches
are held horizontally in a picturesque silhouette and
sometimes can outgrow the central leader forming an
attractive multistemmed specimen tree. Black pine is a
native of Japan. It prefers but does not insist on
colder climates; needs special care if grown in the
warmer regions. It has
rough bark and dark needles. Occasionally a black pine
will have a "witches' broom" growth on a branch caused
by a fungus infection. It is a thick clump of branchlets
having dwarfed foliage. Trees propagated from witches'
brooms make ideal bonsai subjects as they are
characterized by compact foliage and needles which are
very short and erect. Bonsai propagated from witches's
broom stock are called "Yatsubusa".
Lighting: They require full
sun and good air circulation. Turn the tree from time to
time so that light reaches all parts of the foliage.
Temperature: Zone 6 through
8. The black pine does not like extreme heat, especially
in the area of its roots. Spray the foliage with water
daily during the summer.
Watering: May be allowed to
go dry between waterings. Needs good drainage.
Feeding: Fertilize with an
acid based fertilizer.
Pruning and wiring: Do
pruning during the early growing season. On all 2-needle
pines, begin pinching at the end of spring when the buds
have matured. First pinch the undesired weak buds and a
week later pinch the undesired strong ones. (Just
opposite for 5-needle varieties.) Then, as a result of
this first pinching, selectively remove buds in the weak
areas, leaving only the biggest and strongest. In the
strongest areas leave the weak buds, removing the
biggest and strongest. Remove needles growing from the
top and bottom of branches, leaving only lateral
needles. Every other spring, if the tree is healthy, you
can remove all of the new candles. The following fall,
buds will appear where the candles were removed. This
serves to greatly shorten the internodes and increase
Propagation: Black pines
may also be grown from seeds sown in sand in early
April. Seeds should be soaked in water for two days to
hasten germination. Be sure to discard any seeds which
are floating in the water. Black pines may also be
propagated by grafting and from cuttings.
Repotting: Repot in Spring
before the buds begin to swell. A soil mix of coarse
sand, calcinated clay and peat works well. The container
may have to be larger than aesthetics dictate so the
feeder roots do not dry out and die at the end of a
summer day. Don't under pot a black pine. To take up
nourishment, pines need to have a special type of fungus
in the soil around their roots. This fungus appears as a
white, stringy material. When repotting, make sure some
of this helpful fungus is included in the new soil mix.
Pests and diseases: Usually
none serious, except Pine wilt nematode in the east and
tip moth on recently transplanted Pines. The Maskell
scale has recently devastated large numbers of trees in
Some adelgids will appear as white cottony growths on
the bark. All types produce honeydew which may support
sooty mold. European Pine shoot moth causes young shoots
to fall over. Infested shoots may exude resin. The
insects can be found in the shoots during May.
Pesticides are only effective when caterpillars are
moving from overwintering
sites to new shoots. This occurs in mid to late April or
when needle growth is about half developed.
Bark beetles bore into trunks making small holes
scattered up and down the trunk. The holes look like
shotholes. Stressed trees are more susceptible to
attack. Keep trees healthy. Sawfly larvae caterpillars
are variously colored but generally feed in groups on
the needles. Some sawfly larvae will flex or rear back
in unison when disturbed. Sawflies can cause rapid
defoliation of branches if left unchecked.
Pine needle miner larvae feed inside needles causing
them to turn yellow and dry up.
Pine needle scale is a white, elongated scale found on
the needles. Pine tortoise scale is brown and found on
twigs. Depending on the scale, horticultural oil may
control overwintering stages. Pine spittle bug lives and
hides in a foamy mass. Zimmerman Pine moth larvae bore
into the trunk. The only outward symptoms may be death
of parts of the tree or masses of hardened pitch on the
branches. The larvae of Pine weevils feed on the sapwood
of the leaders. The leader is killed and the shoots
replacing it are distorted. First
symptoms are pearl white drops of resin on the leaders.
The leaders die when the shoot is girdled as adults
emerge in summer.
Aphids, mealy bug & red spider. Scale, shoot-tip moths
and beetles may attack the tree and can best be
controlled with a systemic insecticide. Do a preventive
fungicide spray every two to three weeks with Benomyl®
Diseases: This pine is
resistant to Diplodia tip blight.