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Pinus mugo

Mugo Pine, Mugho Pine, or Swiss Mountain Pine

(Pinaceae - Pine Family)

Form

• small- to medium-sized evergreen shrub (in most cases)
• ultimate size is highly dependent upon the cultivar, but the smallest cultivars ultimately mature at about 1.5' tall by 3' wide, and the largest selections in the nursery trade can eventually become very large shrubs (10' tall by 15' wide)
• upright mound or upright flat-top growth habit, spreading at an early age
• slow growth rate

Culture

• full sun to partial shade
• performs best in full sun in moist, well-drained soils but is very adaptable to poor soils, clay soils, sandy soils, dry soils, soils of alkaline pH, and is tolerant of moderate shearing
• propagated by seeds, grafts, or rooted cuttings
• Pine Family, with two serious pests (Pine Sawfly Larvae and Pine Needle Scale) that can be controlled with appropriate monitoring when they occur
• abundantly available, primarily as relatively compact cultivars in container form, but also in ball and burlap form for the larger selections
• newly emergent growth (candles) can be sheared back halfway for even more dense and formal growth the following year
• can be left unpruned if it has ample space to grow in a sunny location, since it is naturally a dense and low-branching shrub, but it is often sited at foundations, and therefore by habit and necessity regularly sheared into a rounded or flat-topped shape
• Pine Sawfly Larvae (green caterpillars with black heads, occurring in masses on individual stems, without an associated tent or webbing), which may infest any of several two-needled Pines in May, prefer Mugo Pine as their favorite delicacy, and can devastate the second- and third-year needles over the entire plant within a two-day period, rendering it to a nearly naked shrub of stems and expanding candle growth; treatment is best achieved by either squishing the caterpillars with one's fingers on a daily basis, or sprays with insecticides or insecticidal soap
• Pine Needle Scale (white elongated "dots", primarily on the older needles) can also be a serious pest problem that builds up over several seasons, and can be remedied by treatment with insecticides or dormant oil at specific times of the year
• Mugo Pine should be used more often as an embankment cover, as its shallow root system and spreading growth habit will combine, over time, to create a solid evergreen cover in sunny, exposed areas
• Mugo Pine can also be used as an effective non-thorny barrier hedge, and either formally sheared to the desired height and width, or informally left alone

Foliage

• two needles per bundle, from 1" to 2" long, persisting for up to five years, maturing to a dark green color

Flowers

• ornamentally inconspicuous, monoecious (separate staminate and pistillate flowers on the same plant), occurring in May but only on mature plants

Fruits

• small cones are relatively rare

Twigs

• attractive light green candles (vertical stems with miniature needles) emerge above the generally flat-topped to rounded canopy in Spring
• twigs mature to be rough (needle-scarred) and black-brown branches with age, often concealed by the dense and long-persistent needles

Trunk

• dark gray, broken into plates on larger specimens, often unseen as the plant is normally a shrub that branches and foliages to the ground

ID Summary

• although highly variable in growth habit and ultimate size in its native habitat, selections of Mugo Pine grown by nurseries are relatively compact or truly dwarf, low-branching, dense shrubs, usually under 5' in height and 10' in width at maturity and often sheared to smaller dimensions anyway
• straight, relatively short needles occur as two per bundle, on stiff, ascending stems that originally radiate from the central trunk at ground level, becoming spreading at an early age and mounding with maturity; sometimes infested repeatedly each Spring with Pine Sawfly Larvae, or continuously with Pine Needle Scale with age

Function

• foundation, entranceway, group planting, embankment, facer, specimen, raised planter, or hedge evergreen shrub

Texture

• medium texture
• thick density

Assets

• low branching and dense evergreen foliage occur to the ground
• attractive candles (new stems) are held prominently above the flat-topped, mounding, or rounded shrub
• slow growth rate (an asset since it is often sited at or near foundations)

Liabilities

• most "dwarf" cultivars get much larger than advertised with age
• two serious pest problems: Pine Sawfly Larvae (alarming cosmetic chewing damage) and Pine Needle Scale (subtle long-term damage that leads to plant decline if untreated)

Habitat

• zones 2 to 7
• native to the Alps in Europe (where it takes on a mixture of shapes and sizes that range from large shrubs to large trees [up to 80' tall])

Variants

• Pinus mugo 'Compacta' - to 5' tall by 8' wide (there may be several selections of this generic term in the trade; all eventually get larger than expected)
• Pinus mugo 'Enci' - slowly maturing to 3' tall by 5' wide, very densely twiggy with short needles, with a table-top growth habit
• Pinus mugo 'Gnome' - a true dwarf form, with shorter, more dense needles and a flat top, slowly maturing to 1.5' tall by 3' wide, sometimes grafted onto a standard

Purpose

• Mugo Pine often serves as a foundation, bed, or specimen evergreen shrub.

Summary

• Pinus mugo is known as a spreading, slow-growing evergreen shrub with ascending branches and relatively short needles, used at foundations and entranceways, on embankments, within rock gardens, as a facer shrub, as formal or informal hedges, and in raised planters, often getting larger than intended, but tolerant of pruning or shearing.

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