Mugo Pine (Swiss Mountain Pine)
- Pinus mugo
Mugo Pine is a shrub or small, round or broad pyramidal
plant 4 to 10 feet tall which grows best in sun or
partial shade in moist loam. It comes from Alpine
Europe. The dark green, 1 - 1 1/2 inches long, stiff
needles of this two-needle Pine are held on the tree for
more than four years making this one of the more dense
Pines suitable for a screen planting. Most other Pines
are not suited for screens since they loose their inner
needles and lower branches as they grow older. Since
there seems to be great variability in height among
individual trees, select nursery plants which have the
form which you desire. When selecting a Mugo Pine to
grow into a tree, choose one with a central leader; if
looking for a more dwarf type Mugo Pine choose among the
many compact selections.
Lighting: Full sun.
Turn the tree from time to time so that all parts of the
foliage receive adequate light.
Temperature: Zones 2
through 7. Will tolerate freezing but roots need to be
Watering: May dry
out between waterings. Fast draining soil to avoid root
rot. Spray the foliage with water daily during the
Feeding: Simon and
Schuster's recommends feeding once a month in spring and
autumn using a slow-acting organic fertilizer. If you
prefer to feed using chemical fertilizers, feed the tree
once every two weeks with a half-strength solution of a
fertilizer meant for
acid-loving plants, such as Miracid. Suspend feeding for
two months during the hot part of summer (July and
August in the northern hemisphere). Do not feed if the
tree is ailing or has been repotted recently (2-4
Pruning and wiring:
Initial pruning should be carried out at the same time
as repotting. When repotting, be sure to leave a good
root system. Subsequent pruning can be carried out when
wiring in the fall. Pinch by shortening new shoots
(candles) by two thirds in the spring,before the needles
open. Pinch the candles in two stages, pinching the most
vigorous candles first and a week later pinching the
weaker candles. In the fall, reduce the number of buds
on each branch to two to encourage ramification. Also in
the fall, thin the needles by removing any needles that
are too long or that are growing downward. Thin more at
the apex of the tree and less as you work down the tree.
This will allow light to reach the lower branches and
will slow the growth of the apex.
Wiring should be done in late fall or early winter, and
the wire removed 6-8 months later at most. With healthy
trees, it is possible to remove all the new candles
other year, before they harden. The following fall, buds
will appear where the candles were removed. This serves
to shorten the internodes and encourage more dense
Repotting: In early
spring or late summer, every 2-3 years for young
specimens and every 3-5 years for older ones. Pines need
deep, well drained soil, so plant in a fairly deep
container. Simon and Schuster's recommends 50% soil and
50% coarse sand. Rémy Samson recommends 1 part leaf
mould, 1 part loam, and 1 part coarse sand.
Peter Chan recommends 1 part loam, 1 part peat, and 3
parts coarse sand. Pines and other conifers grow in
association with a symbiotic fungus which grows in the
root ball of the tree. If this fungus is not present,
the tree may die. For this reason, pines and other
conifers should never be bare-rooted, unless steps are
taken to re-introduce the fungus to the repotted plant,
such as making a slurry (thin mud) of the old soil and
pouring it over the newly potted soil. Some experts feel
that it is more important to be sure that the tree
always has a healthy root system with sufficient feeder
roots than to
worry about symbiotic fungi. They feel that trees are
more likely to die from having their root systems
reduced too much at once than from not having the fungus
present. Certainly it is good advice in any case to be
sure the tree has sufficient roots.
Pests and diseases: Pests:
Mugo Pine is a favored host for Pine sawfly and Pine
needle scale. 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.
Stressed trees are more susceptible to attack. The holes
look like shotholes. 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.
Spruce mites cause damage to older needles, and are
usually active in the spring and fall. Mites cause older
needles to become yellowed or stippled. 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 August. Prune out and burn infested
terminals before July 15. Pine wilt nematode can kill
tip blight is a common problem and Mugo Pine is very
sensitive. This pine is susceptible to rusts. Canker
diseases may rarely cause dieback of landscape Pines.
Keep trees healthy and prune out the infected branches.
Needle cast is common on small trees and plantation or
forest trees. Infected needles yellow and fall off.