mugo has something of a poor reputation as bonsai, with the
correct techniques, Mugos are easy to cultivate and style.
Mugo pines (also known as Mountain Pines) are easily available at garden centres and nurseries compared to most pine species. It is recommended that the plain Mugo Pine is used as Mugo varieties tend to be weaker and unresponsive in comparison. Try to find ordinary landscape pines rather than the miniature rock-garden varieties such as P. mugo 'Mops' and 'Valley Cushion' that are known as being particularly touchy to bonsai cultivation.
Mugo pine care
Mugos like plenty of light and water to achieve their full potential, however they must have a fast draining soil so that their roots don't sit in water. For maximum health and vigour, feed Mugos strongly with slow release fertiliser from Spring through to late Summer.
Repotting Mugo Pines
mugo has a bad reputation for reacting badly to repotting and
rootpruning. It is not unusual to hear of Mugos becoming weak
or even dying after a Spring repotting.
Unlike the timing for the Japanese Black Pine which is normally repotted as they come into active growth (the candles have extended and the new needles can be seen held tight against the candle). Mugo pines react far better to Summer repotting.
Following comments I read on the internet last year that Mugos dislike being repotted in early Spring and respond strongly to be repotted while active in the Summer, I repotted 3 Mugos last August with great success. The Mugo pine appears to be one of a few tree species that actually prefer repotting and rootpruning during the growing season.
ideal repotting time would seem to be after the first flush
of growth has extended and is cut back (see below) and before
the end of the Summer; this equates to July and August in most
With a healthy mugo, all of any old, poor draining soil that is found can be removed by hand but do not wash the roots. This allows new, fast draining soil to be introduced around the rootball without removing the natural mycarrhizae attached to the roots. If you have any doubts as to the strength of the tree, only remove 50% of any old compacted soil that is found, removing the remainder in the next repotting.
It is not necessary to prune any of the foliage of the pine after rootpruning to 'balance' the tree. The waxy needles of a Pine require relatively little moisture uptake from the roots, there is no need to try and reduce transpiration through the removal of above-ground growth. The more foliage the tree has after rootpruning, the more strength it will have to repair and regenerate the rootmass. The tree will 'balance' the roots and foliage itself.
After repotting during the Summer, if temperatures in your climate are above an average 80°F (approx) keep the tree out of direct sun for a couple of weeks (only) and lightly mist the foliage a couple of times a day, otherwise no special provision is necessary.
Insulting a Pine
Healthy and vigorous, immature landscape or garden centre Mugos can be repotted, pruned and wired all at the same time after the first flush of growth through to early September. However,after this initial styling, the tree then will require 2 or 3 years to recover.
Be wary of reducing a nursery Pine's top growth by more than 50% in one vegetative period. Reduce the height of the trunk (and foliage) slowly in comparison to deciduous tree species.
Mature Mugos are much like other Pine species in that they will
only take one major working every year.
The general rule with mature (over 30-40 years) Pines is to keep to 'only one insult per vegetative period'. After repotting or drastic pruning or wiring or styling you must then wait until 12 months elapses before carrying out any further work. This also means that if a Pine is styled in the Summer, it cannot be repotted the following Spring.
Immature pines can be worked much harder and it is possible to get away with less time for recovery but it is important to respect that Pines must always be worked slowly.
Mugo Pine Pruning
The buds of the left-hand illustration are reduced to 2 weak buds for strong branches (middle image) or the strongest 2 buds for weaker branches (right hand image).
As with other Pine species, the number of buds at any one point on a branch is always reduced to 2 so that the branch forks into two sub-branches. Remove excess buds as and when they appear. (For more information on Pine bud selection and Areas of Apical Vigour and Weakness see Pruning Pines)
Bud selection on a Mugo Pine is required in early Spring and during the Summer after the first flush of growth is cut back.