Xtremehorticulture

How to Rehabilitate Japanese Black Pine

Q. Are Black Pine, California Christmas Tree and
Thumbergii all the same plant? I have 2 trees that are important in my
landscape and have been doing well for several years. They were neglected
recently so there is no place for deep watering and not fertilized in 2015.
There is sap coming from the trunk. Should I try to rehabilitate them or
replace them?
Japanese Black Pine

A. Japanese black pine is Pinus thunbergii so
Thunbergii probably refers to Japanese black pine. I do not know if it is
called California Christmas tree but I doubt it because Japanese black pine has
a very unusual form making it a specimen plant in the landscape. It does not
have the Christmas tree shape.
          Most
of the textbooks say Japanese black pine tolerates alkaline soils but I have
not really found them to be very tolerant of the hot desert and our soils. Many
of them have been planted in Las Vegas but very few are still around which
tells me many were removed.
          If
you have Japanese black pine they are characteristically slow in growth and
have a very distinguished form that adds character to a landscape. If you are
looking for a Christmas tree pine this is not going to be it.
          They
are slow-growing. If they have been neglected and do not look good they will
rehabilitate very slowly. 
          Soil
applied systemic insecticides that control borers would be a good if the trees
actually have them. Pines can be “sappy” so make sure it is borers before you
make the application. Wounding of the trunk and limbs can also cause them to
bleed sap like borer damage.
          If
you choose to rehabilitate them, put tree wells around the trunk about 2 feet
in diameter to hold irrigation water. Give them a deep soaking with a hose once
a month along with their normal irrigations.
          Fertilize
them with 16–16–16 once a year in the early spring or apply it now if they
haven’t been fertilized this year. Punch some holes in the soil 2 to 4 feet
from the trunk to a depth of eight or 10 inches. Put a handful of fertilizer in
each of the holes and water them twice to activate the fertilizer and move it
into the tree.

          Expect
a very slow recovery if you choose to rehabilitate them. If they look bad now,
I would suggest that you consider replacing them with something that you really
like and can get instant gratification.

1 thought on “How to Rehabilitate Japanese Black Pine”

Leave a Comment

Your email address will not be published. Required fields are marked *